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Menstruation is a complex physiological process controlled by coordinated communication between the hypothalamus, pituitary gland, ovaries, and uterus. For many people, menstrual bleeding follows a predictable pattern, but the cycle can become irregular for numerous reasons, ranging from normal physiological changes to endocrine disorders, pregnancy, medications, structural abnormalities, chronic disease, and disorders of ovulation.

Menstrual irregularities are therefore not a single disease. They are a clinical sign or group of symptoms that may indicate an underlying condition.

Irregular menstruation may appear as:

Periods occurring too frequently
Periods occurring too far apart
Missed periods
Very heavy menstrual bleeding
Very light periods
Bleeding lasting unusually long
Spotting between periods
Bleeding after sexual intercourse
Sudden changes in a previously regular cycle
Complete absence of menstruation

The World Health Organization emphasizes that menstrual bleeding that is unpredictable, infrequent, very painful, heavy, or disruptive to daily activities can sometimes indicate an underlying condition requiring evaluation.

This comprehensive article explains menstrual irregularities from basic physiology to causes, clinical presentation, investigations, PCOS, thyroid disease, hyperprolactinemia, pregnancy-related causes, treatment options, complications, adolescent menstrual disorders, perimenopause, and practical clinical cases.

What Are Menstrual Irregularities?

Menstrual irregularities occur when menstrual bleeding differs significantly from an individual's expected or previously established pattern in terms of:

Frequency
Regularity
Duration
Volume
Timing

A menstrual cycle is counted from the first day of bleeding of one period to the first day of the next period.

For many adults, a typical menstrual cycle is approximately 21–35 days, and a period commonly lasts up to 7 days.

However, menstrual patterns vary among individuals and across different stages of life.

Therefore, the word “irregular” should not automatically mean “disease.”

The clinical question is:

Is this pattern appropriate for the person's age and physiological situation, or does it suggest an underlying disorder?

Normal Menstrual Cycle

Understanding the normal menstrual cycle is essential for understanding menstrual irregularities.

The menstrual cycle is regulated by the:

Hypothalamus → Pituitary → Ovary → Endometrium

This is commonly called the:

Hypothalamic–Pituitary–Ovarian axis

The Hypothalamus

The hypothalamus releases:

Gonadotropin-releasing hormone — GnRH

GnRH stimulates the anterior pituitary gland.

GnRH is released in a pulsatile manner.

The frequency and amplitude of GnRH pulses influence secretion of:

The Pituitary Gland

The anterior pituitary produces two major reproductive hormones:

Follicle-stimulating hormone — FSH

FSH promotes:

Follicular development
Granulosa cell activity
Estrogen production

Luteinizing hormone — LH

LH contributes to:

Follicular maturation
Ovulation
Corpus luteum formation
Progesterone production

The Ovary

The ovary produces:

Estrogen
Progesterone
Androgens

These hormones regulate the endometrium and influence the timing and characteristics of menstruation.

The Endometrium

The endometrium is the inner lining of the uterus.

During the cycle it undergoes:

Proliferation
Secretory transformation
Breakdown and shedding

If pregnancy does not occur, progesterone levels fall after corpus luteum regression.

This hormonal withdrawal contributes to:

Menstruation

Main Phases of the Menstrual Cycle

The cycle is commonly divided into:

Menstrual phase
Follicular/proliferative phase
Ovulation
Luteal/secretory phase

1. Menstrual Phase

The endometrial lining is shed.

This produces menstrual bleeding.

2. Follicular Phase

FSH stimulates development of ovarian follicles.

Developing follicles produce increasing amounts of estrogen.

Estrogen stimulates:

Endometrial proliferation

3. Ovulation

When estrogen remains sufficiently elevated for an appropriate period, feedback on the hypothalamic-pituitary system changes.

This contributes to the:

LH surge

The LH surge triggers ovulation.

4. Luteal Phase

After ovulation, the follicle becomes the:

Corpus luteum

The corpus luteum produces progesterone.

Progesterone:

Stabilizes the endometrium
Converts proliferative endometrium into secretory endometrium
Prepares the uterus for possible implantation

If pregnancy does not occur:

Corpus luteum regresses → progesterone falls → endometrial breakdown → menstruation

Why Menstrual Cycles Become Irregular

Menstrual regularity depends on several systems functioning correctly.

A disturbance at almost any point can alter menstruation.

For example:

Hypothalamic dysfunction

↓

Reduced GnRH pulsatility

↓

Reduced FSH/LH stimulation

↓

Reduced ovarian hormone production

↓

Absent or irregular ovulation

↓

Irregular menstruation

Alternatively:

PCOS

↓

Chronic ovulatory dysfunction

↓

Irregular/infrequent menstruation

How Common Are Menstrual Irregularities?

Menstrual irregularities are common across the reproductive lifespan.

They are particularly common during:

The first few years after menarche
Pregnancy
Breastfeeding
Perimenopause

They may also occur with:

PCOS
Thyroid disorders
Hyperprolactinemia
Excessive exercise
Low energy availability
Eating disorders
Obesity
Stress
Certain medications
Structural uterine disease
Bleeding disorders

ACOG notes that irregular bleeding can occur at different stages of life, including adolescence and perimenopause, although persistent or significant abnormalities still warrant appropriate evaluation.

Terminology Used for Menstrual Irregularities

Several terms are commonly encountered in medical literature.

Amenorrhea

Complete absence of menstrual periods.

It is divided into:

Primary amenorrhea
Secondary amenorrhea

Oligomenorrhea

Infrequent menstrual periods.

The term is often used clinically for cycles occurring at unusually long intervals.

Polymenorrhea

Menstrual bleeding occurring at unusually short intervals.

Menorrhagia

Historically used to describe excessive menstrual blood loss occurring at regular intervals.

Modern terminology increasingly uses:

Heavy menstrual bleeding — HMB

Metrorrhagia

Historically referred to bleeding occurring between expected menstrual periods.

Menometrorrhagia

Historically described both:

Excessive menstrual bleeding
Irregular/intermenstrual bleeding

Modern terminology generally uses more precise descriptions such as abnormal uterine bleeding.

Abnormal Uterine Bleeding

A broader modern clinical term is:

Abnormal uterine bleeding — AUB

ACOG describes abnormal uterine bleeding as bleeding that differs from normal in timing, frequency, duration, or amount. It can include bleeding between periods, bleeding after sex, heavy menstrual bleeding, cycles shorter than 21 days or longer than 35 days, and prolonged absence of periods.

When Is a Menstrual Cycle Considered Abnormal?

In adults, features that should prompt consideration of evaluation include:

Cycles consistently shorter than 21 days
Cycles consistently longer than 35 days
Large variation in cycle length
Periods lasting more than 7 days
Very heavy bleeding
Bleeding between periods
Bleeding after sex
Periods separated by several months
Sudden change from a previously regular pattern

ACOG identifies cycles shorter than 21 days or longer than 35 days and significant cycle-to-cycle variation as examples of abnormal uterine bleeding.

Heavy Menstrual Bleeding

Heavy menstrual bleeding is more than simply having a “heavy period.”

It becomes clinically important when bleeding:

Interferes with daily life
Causes fatigue
Produces anemia
Requires very frequent product changes
Persists for more than about 7 days
Causes social, educational, occupational, or physical limitations

ACOG lists bleeding lasting more than 7 days and soaking through pads or tampons approximately every hour for several hours as signs of heavy menstrual bleeding.

NICE emphasizes that assessment should consider the impact of heavy bleeding on quality of life, rather than focusing only on estimated blood volume.

Major Causes of Menstrual Irregularities

The causes can be divided into several broad categories.

1. Physiological causes

Early adolescence
Pregnancy
Breastfeeding
Perimenopause

2. Ovulatory disorders

PCOS
Hypothalamic dysfunction
Hyperprolactinemia
Thyroid disorders
Primary ovarian insufficiency

3. Structural causes

Fibroids
Endometrial polyps
Adenomyosis
Endometrial abnormalities

4. Pregnancy-related causes

Normal pregnancy
Miscarriage
Ectopic pregnancy

5. Medications

Hormonal contraceptives
Anticoagulants
Some psychiatric medications
Certain endocrine medications

6. Systemic disease

Thyroid disease
Liver disease
Kidney disease
Chronic inflammatory disease

7. Hematological disorders

von Willebrand disease
Platelet disorders
Other coagulation disorders

8. Lifestyle and energy imbalance

Excessive exercise
Rapid weight loss
Low caloric intake
Eating disorders
Severe psychological stress

The PALM-COEIN Classification

For abnormal uterine bleeding in reproductive-age patients, a useful FIGO framework is:

PALM

These represent structural causes:

P — Polyp
A — Adenomyosis
L — Leiomyoma
M — Malignancy and hyperplasia

COEIN

These represent mainly nonstructural causes:

C — Coagulopathy
O — Ovulatory dysfunction
E — Endometrial
I — Iatrogenic
N — Not otherwise classified

This classification is particularly useful for organizing the differential diagnosis of abnormal uterine bleeding.

P — Endometrial Polyps

Endometrial polyps are localized overgrowths of endometrial tissue.

They may cause:

Irregular bleeding
Intermenstrual bleeding
Heavy periods
Postmenopausal bleeding

Small polyps may produce no symptoms.

When a uterine cavity lesion is suspected, hysteroscopy can be particularly useful because it allows direct visualization and may permit treatment during the same procedure. NICE recommends outpatient hysteroscopy when symptoms suggest submucosal fibroids, polyps, or endometrial pathology.

A — Adenomyosis

Adenomyosis occurs when endometrial-type tissue is present within the muscular wall of the uterus.

Typical features include:

Heavy menstrual bleeding
Painful menstruation
Enlarged or bulky uterus
Pelvic pain

NICE recommends transvaginal ultrasound as the preferred first-line imaging test when adenomyosis is suspected because of significant dysmenorrhea or a bulky, tender uterus.

L — Leiomyoma

Leiomyomas are commonly called:

Fibroids

They are benign tumors of uterine smooth muscle.

Depending on their size and location, they can cause:

Heavy menstrual bleeding
Pelvic pressure
Pelvic pain
Urinary symptoms
Constipation
Infertility
Recurrent pregnancy problems

Why Does Fibroid Location Matter?

Not all fibroids cause the same symptoms.

Submucosal fibroid

Projects toward the uterine cavity.

It is particularly associated with:

Heavy bleeding
Irregular bleeding
Fertility problems

Intramural fibroid

Located within the uterine muscular wall.

Subserosal fibroid

Projects toward the outer surface of the uterus.

It may produce:

Pressure symptoms
Pelvic fullness

M — Malignancy and Endometrial Hyperplasia

Although malignancy is less common than benign causes, it must not be overlooked.

Abnormal uterine bleeding can be a presenting symptom of:

Endometrial hyperplasia
Endometrial intraepithelial neoplasia
Endometrial cancer

ACOG notes that abnormal uterine bleeding is the most common symptom of endometrial hyperplasia.

Risk increases with factors such as:

Increasing age
Obesity
Chronic anovulation
PCOS
Prolonged unopposed estrogen exposure
Certain medications
Family history of endometrial cancer

C — Coagulopathy

Bleeding disorders should be considered when heavy menstrual bleeding:

Began from the first periods
Is unusually severe
Is associated with easy bruising
Is associated with frequent nosebleeds
Causes excessive bleeding after dental procedures or surgery
Is present in other family members

A classic example is:

von Willebrand disease

ACOG notes that heavy bleeding from the beginning of menstruation combined with a personal or family history suggestive of a bleeding disorder should prompt consideration of coagulation evaluation.

O — Ovulatory Dysfunction

Ovulatory dysfunction is one of the most important causes of irregular menstruation.

If ovulation does not occur regularly:

↓ Progesterone exposure

↓

Endometrium remains exposed to estrogen without normal cyclic progesterone

↓

Irregular endometrial growth and shedding

↓

Irregular and sometimes heavy bleeding

Conditions associated with ovulatory dysfunction include:

PCOS
Thyroid disease
Hyperprolactinemia
Hypothalamic dysfunction
Perimenopause
Obesity
Eating disorders

E — Endometrial Causes

Sometimes abnormal bleeding occurs even when there is no obvious structural abnormality and ovulation is occurring.

The problem may involve:

Local endometrial hemostasis
Inflammatory mediators
Vascular regulation
Prostaglandin pathways

These cases can be difficult to identify because imaging may be normal.

I — Iatrogenic Causes

“Iatrogenic” means caused by medical treatment or intervention.

Examples include:

Hormonal contraceptives
Copper IUD
Hormone therapy
Anticoagulants
Some medications affecting endocrine pathways

ACOG specifically notes that hormonal contraception can produce breakthrough bleeding and that anticoagulants and aspirin may contribute to heavier bleeding.

N — Not Otherwise Classified

This category includes less common causes that do not fit neatly into the other groups.

Examples may include:

Certain uterine vascular disorders
Chronic endometritis
Cesarean scar-related abnormalities
Other uncommon conditions

Menstrual Irregularities Due to PCOS

One of the most important causes of irregular menstruation is:

Polycystic Ovary Syndrome

PCOS is a common endocrine and metabolic disorder.

The World Health Organization estimates that PCOS affects approximately 10–13% of reproductive-aged women worldwide, with many affected individuals remaining undiagnosed.

Why Does PCOS Cause Irregular Periods?

PCOS is commonly associated with:

Hyperandrogenism
Abnormal follicular development
Ovulatory dysfunction
Insulin resistance in many patients

This may produce:

Irregular ovulation

↓

Irregular progesterone exposure

↓

Irregular endometrial shedding

↓

Irregular periods

Symptoms Suggesting PCOS

Possible features include:

Irregular periods
Infrequent periods
Amenorrhea
Difficulty becoming pregnant
Excess facial or body hair
Acne
Oily skin
Scalp hair thinning
Weight gain or obesity in some patients
Insulin resistance
Acanthosis nigricans

WHO notes that PCOS can produce irregular or absent periods, hyperandrogenic symptoms, infertility, acne, and metabolic complications.

Important PCOS Myth

A woman does not need to have visible ovarian cysts to have PCOS.

Diagnosis is based on the overall clinical picture and exclusion of alternative causes.

WHO notes that some women with PCOS do not have polycystic ovaries and that ovarian cysts are not required for diagnosis.

Menstrual Irregularities and Thyroid Disease

Both:

Hypothyroidism

and

Hyperthyroidism

can disrupt menstruation.

Possible menstrual effects include:

Irregular periods
Heavy bleeding
Infrequent periods
Amenorrhea

Thyroid hormones interact with reproductive endocrine pathways, and thyroid dysfunction can interfere with normal ovulation.

ASRM recommends TSH as part of the initial assessment of many patients presenting with amenorrhea or menstrual abnormalities.

Menstrual Irregularities and Hyperprolactinemia

Prolactin is primarily associated with:

Lactation
Breast development
Reproductive regulation

Excess prolactin can suppress reproductive signaling.

Possible symptoms include:

Irregular periods
Amenorrhea
Infertility
Galactorrhea
Reduced libido

Causes include:

Prolactinoma
Certain medications
Hypothyroidism
Physiological factors

ASRM recommends considering prolactin measurement in patients with amenorrhea and menstrual irregularities.

Menstrual Irregularities Due to Pregnancy

Pregnancy should be considered whenever a person of reproductive potential has a missed period or unexpected bleeding.

Possible pregnancy-related causes of bleeding include:

Implantation-related bleeding
Threatened miscarriage
Miscarriage
Ectopic pregnancy
Other pregnancy complications

Therefore:

Pregnancy testing is one of the first steps in evaluating secondary amenorrhea.

ASRM specifically states that pregnancy should be the first consideration in secondary amenorrhea.

Ectopic Pregnancy

An ectopic pregnancy occurs when implantation occurs outside the normal uterine cavity, most commonly in a fallopian tube.

Possible symptoms include:

Missed period
Vaginal bleeding
Unilateral pelvic pain
Shoulder pain in some cases
Dizziness
Syncope
Hemodynamic instability

A ruptured ectopic pregnancy is an emergency.

Menstrual Irregularities and Weight Changes

Both significant weight loss and weight gain can affect menstrual cycles.

Rapid weight loss

Can suppress hypothalamic GnRH secretion.

This may result in:

↓ GnRH → ↓ LH/FSH → ↓ ovarian activity → amenorrhea

Excessive Exercise

High levels of physical activity combined with insufficient energy intake can disrupt the hypothalamic-pituitary-ovarian axis.

This may lead to:

Oligomenorrhea
Amenorrhea
Low estrogen levels

ACOG recognizes excessive exercise and eating disorders among possible causes of abnormal periods.

Functional Hypothalamic Amenorrhea

Functional hypothalamic amenorrhea can occur when reproductive function is suppressed in response to factors such as:

Low energy availability
Significant weight loss
Excessive exercise
Psychological stress

It is important because prolonged hypoestrogenism can affect:

Bone health
Fertility
Cardiovascular health

Eating Disorders

Conditions such as anorexia nervosa can cause profound menstrual dysfunction.

Energy depletion affects:

Leptin signaling
GnRH pulsatility
LH secretion
Ovarian estrogen production

ACOG considers menstrual disturbance an important clinical sign in adolescents and young women with eating disorders.

Stress and Menstrual Irregularities

Psychological stress can influence hypothalamic function.

Severe or prolonged stress may contribute to:

Delayed menstruation
Irregular cycles
Amenorrhea

However, stress should not automatically be blamed for persistent menstrual abnormalities.

A clinician should still consider:

Pregnancy
PCOS
Thyroid disease
Hyperprolactinemia
Ovarian insufficiency
Structural disease

Menstrual Irregularities in Adolescents

Menstrual irregularity is relatively common during the first years after menarche because the hypothalamic-pituitary-ovarian axis is still maturing.

However:

Not every irregular period in an adolescent should be dismissed as “normal puberty.”

ACOG considers the menstrual cycle an important vital sign in adolescent health.

When Should an Adolescent Be Evaluated?

Important warning patterns include:

Periods consistently more than 90 days apart
Very heavy bleeding
Bleeding lasting more than 7 days
Symptoms of anemia
Severe pelvic pain
Signs of hyperandrogenism
Significant weight loss
Eating disorder symptoms
Possible pregnancy
Excessive bruising or bleeding elsewhere

ACOG notes that although longer intervals can occur during adolescence, going more than about 90 days without menstruation is uncommon and warrants evaluation.

Menstrual Irregularities During Perimenopause

Perimenopause is the transition toward menopause.

During this period:

Ovulation becomes less predictable
Cycle length can change
Periods may become heavier or lighter
Periods may occur closer together or farther apart

Although irregularity becomes more common, significant or unusual bleeding should not automatically be attributed to perimenopause.

Structural abnormalities and endometrial pathology may still need evaluation.

Menstrual Irregularities After Menopause

Any vaginal bleeding after menopause requires evaluation.

Postmenopausal bleeding can result from:

Vaginal or endometrial atrophy
Polyps
Endometrial hyperplasia
Endometrial cancer
Other gynecological conditions

Bleeding after menopause should not simply be assumed to be “another period.”

Menstrual Irregularities and Medications

A detailed medication history is essential.

Potential contributors include:

Hormonal contraceptives
Copper IUD
Anticoagulants
Antiplatelet medications
Aspirin
Certain antipsychotics
Some antidepressants
Certain endocrine medications

ACOG emphasizes reviewing both prescription and over-the-counter medications when evaluating abnormal uterine bleeding.

Hormonal Contraceptives and Irregular Bleeding

Hormonal contraception can cause changes in bleeding patterns, especially after initiation or changes in the method.

Possible patterns include:

Spotting
Breakthrough bleeding
Lighter periods
Fewer periods
Complete amenorrhea with some methods

These changes may be expected depending on the contraceptive.

However, new or persistent bleeding should be assessed when clinically appropriate.

Copper IUD

Copper intrauterine devices can increase menstrual bleeding, particularly during the first year of use.

Patients experiencing problematic bleeding may require:

Assessment for other causes
Symptomatic treatment
Discussion of alternative contraception

How Is Menstrual Irregularity Diagnosed?

Diagnosis begins with:

1. Detailed history

↓

2. Physical examination

↓

3. Pregnancy exclusion

↓

4. Targeted laboratory testing

↓

5. Imaging when indicated

↓

6. Endometrial evaluation when appropriate

The goal is not to order every test for every patient.

Instead:

Investigations should be guided by the bleeding pattern, age, symptoms, examination, pregnancy possibility, and suspected cause.

Menstrual History

A good menstrual history should include:

Age at menarche
Date of last menstrual period
Typical cycle length
Shortest cycle
Longest cycle
Duration of bleeding
Amount of bleeding
Presence of clots
Intermenstrual bleeding
Postcoital bleeding
Pain
Previous regularity
Recent changes

Menstrual Diary

A menstrual diary can be extremely useful.

Record:

Feature	What to record
Date	First day of bleeding
Duration	Number of bleeding days
Flow	Light/moderate/heavy
Spotting	Yes/no
Pain	Mild/moderate/severe
Clots	Present/absent
Medication	What was taken
Associated symptoms	Fatigue, dizziness, etc.

ACOG recommends keeping track of bleeding dates, duration, and flow because this information can help clinicians evaluate abnormal bleeding.

Important Questions in History

A clinician may ask:

“Were your periods previously regular?”

A sudden change is more concerning than a lifelong stable pattern.

“Could you be pregnant?”

This is essential.

“How heavy is the bleeding?”

Ask about:

Pad/tampon frequency
Night-time changes
Leakage
Clots
Duration

“Do you have pelvic pain?”

May suggest:

Adenomyosis
Endometriosis
Fibroids
PID

“Do you have excess facial hair or acne?”

May suggest androgen excess/PCOS.

“Do you have nipple discharge?”

May suggest hyperprolactinemia.

“Have you recently lost weight or increased exercise?”

May suggest hypothalamic dysfunction.

Physical Examination

Depending on the presentation, examination may include:

General appearance
BMI
Blood pressure
Signs of anemia
Thyroid examination
Skin examination
Signs of hyperandrogenism
Galactorrhea assessment
Abdominal examination
Pelvic examination when indicated

Signs of Hyperandrogenism

Look for:

Hirsutism
Acne
Androgenic alopecia
Deepening voice
Increased muscle mass
Clitoromegaly

Rapid virilization is particularly concerning and may require evaluation for an androgen-secreting tumor.

Signs of Thyroid Disease

Possible findings include:

Hypothyroidism

Fatigue
Weight gain
Cold intolerance
Constipation
Dry skin
Bradycardia

Hyperthyroidism

Weight loss
Heat intolerance
Tremor
Palpitations
Anxiety
Tachycardia

But menstrual irregularity may sometimes occur without obvious thyroid symptoms.

Laboratory Investigations

Testing depends on the suspected diagnosis.

Commonly considered investigations include:

Pregnancy test

Often the first test.

CBC

Especially important in heavy menstrual bleeding.

TSH

When thyroid disease is suspected or when evaluating amenorrhea/menstrual dysfunction.

Prolactin

When amenorrhea, oligomenorrhea, or galactorrhea suggests hyperprolactinemia.

FSH and LH

Useful in selected cases of amenorrhea or suspected ovarian dysfunction.

Estradiol

Can help characterize hypoestrogenic states.

Testosterone

When hyperandrogenism is suspected.

DHEAS

May help evaluate adrenal androgen excess.

17-hydroxyprogesterone

May be considered when congenital adrenal hyperplasia is suspected.

ASRM describes pregnancy testing, FSH/LH, estradiol, prolactin, TSH, and targeted androgen testing as important components of appropriately selected amenorrhea evaluations.

CBC and Menstrual Irregularities

CBC is particularly important when bleeding is heavy or prolonged.

It can detect:

Anemia
Hemoglobin reduction
Platelet abnormalities
Other hematological clues

NICE recommends a full blood count for all women being evaluated for heavy menstrual bleeding.

Iron Deficiency

Chronic heavy menstrual bleeding can produce:

Iron-deficiency anemia

Symptoms may include:

Fatigue
Weakness
Dizziness
Headache
Reduced exercise tolerance
Palpitations
Shortness of breath

Severe iron deficiency can affect quality of life and cognitive performance.

Should Ferritin Always Be Tested?

Not necessarily.

Guidelines differ depending on the clinical context.

NICE does not recommend routine ferritin testing for every woman with heavy menstrual bleeding, while clinicians may still order iron studies when iron deficiency is suspected based on the clinical situation.

Thyroid Testing

Thyroid testing should be guided by the clinical presentation.

For amenorrhea, ASRM considers TSH a first-line screening test.

For isolated heavy menstrual bleeding without other symptoms of thyroid disease, NICE does not recommend routine thyroid hormone testing.

This illustrates an important principle:

The correct test depends on the clinical presentation.

Pelvic Ultrasound

Ultrasound is one of the most commonly used imaging techniques for menstrual abnormalities.

It can help identify:

Fibroids
Adenomyosis
Ovarian abnormalities
Endometrial abnormalities
Pelvic masses

NICE recommends pelvic ultrasound when the examination suggests a pelvic mass, enlarged uterus, or when adenomyosis or other structural disease is suspected.

Transvaginal Ultrasound

Transvaginal ultrasound provides high-quality imaging of pelvic structures.

It may be particularly useful for:

Uterine abnormalities
Endometrial assessment
Ovaries
Adenomyosis
Fibroids

It is generally preferred over transabdominal ultrasound for suspected adenomyosis in appropriate patients.

Hysteroscopy

Hysteroscopy involves inserting a small camera through the cervix into the uterus.

It allows direct visualization of the uterine cavity.

It can detect:

Polyps
Submucosal fibroids
Endometrial abnormalities

In selected cases, treatment can be performed during the same procedure.

Endometrial Biopsy

Endometrial sampling may be indicated when there is concern for:

Endometrial hyperplasia
Endometrial cancer
Persistent abnormal bleeding
Certain high-risk clinical scenarios

NICE recommends obtaining endometrial samples in the context of hysteroscopy rather than using blind biopsy alone for heavy menstrual bleeding.

When Is Endometrial Cancer a Concern?

Consider endometrial pathology when there is:

Persistent abnormal bleeding
Intermenstrual bleeding
High-risk factors
Bleeding after menopause
Obesity with prolonged anovulation
PCOS with prolonged irregular cycles
Failure of appropriate treatment

ACOG notes that abnormal uterine bleeding can be a sign of endometrial cancer and that evaluation is particularly important when risk factors are present.

Treatment of Menstrual Irregularities

Treatment depends entirely on the cause.

There is no single “menstrual irregularity medicine.”

Treatment may include:

Lifestyle modification
Iron replacement
Hormonal therapy
Non-hormonal therapy
Treatment of thyroid disease
Treatment of hyperprolactinemia
PCOS management
Treatment of fibroids or polyps
Surgical treatment
Fertility treatment

Treatment Principle

The correct approach is:

Identify the cause

↓

Treat the cause

↓

Control symptoms

↓

Prevent recurrence

↓

Protect fertility and long-term health

Treatment of Heavy Menstrual Bleeding

Depending on the cause and patient's reproductive goals, options may include:

Levonorgestrel-releasing intrauterine system
Tranexamic acid
NSAIDs
Combined hormonal contraception
Cyclical oral progestogens
Progestogen-only contraception
Treatment of fibroids
Endometrial ablation in selected patients
Hysterectomy in selected cases

NICE recommends an LNG-IUS as a first treatment for many women with heavy menstrual bleeding when there is no identified pathology, small non-cavity-distorting fibroids, or suspected/diagnosed adenomyosis.

Levonorgestrel-Releasing Intrauterine System

The LNG-IUS releases progestogen locally within the uterus.

It can:

Thin the endometrium
Reduce menstrual blood loss
Provide contraception

It is an important treatment option for many patients with heavy menstrual bleeding.

Tranexamic Acid

Tranexamic acid is an antifibrinolytic medication.

It works by reducing the breakdown of fibrin clots.

This can reduce menstrual blood loss.

It is particularly useful because it:

Is non-hormonal
Is taken during bleeding
Does not act as contraception

Its use must be individualized, particularly in patients with thrombotic risk.

NSAIDs

NSAIDs can reduce menstrual bleeding and menstrual pain in some patients.

They reduce prostaglandin synthesis.

However, they may not be appropriate for patients with:

Certain gastrointestinal disorders
Significant kidney disease
NSAID hypersensitivity
Some cardiovascular conditions
Other contraindications

NICE lists NSAIDs as one of the non-hormonal options for heavy menstrual bleeding.

Combined Hormonal Contraceptives

Combined hormonal contraception contains:

Estrogen
Progestogen

It can regulate bleeding and reduce menstrual blood loss.

It may also provide:

Contraception
Reduction in dysmenorrhea
Improvement in acne in some patients

However, estrogen-containing methods are contraindicated in certain clinical situations, such as some thrombotic conditions.

Progestogens

Progestogen therapy can be useful for:

Anovulatory bleeding
Endometrial protection
Cycle regulation
Certain PCOS-related menstrual abnormalities

In chronic anovulation, progesterone/progestogen exposure is important because prolonged unopposed estrogen can contribute to endometrial hyperplasia.

PCOS Treatment

Treatment depends on the patient's goals.

If pregnancy is not currently desired

Management may focus on:

Cycle regulation
Endometrial protection
Hyperandrogenic symptoms
Metabolic health

Options may include:

Combined hormonal contraception
Progestogen therapy
Lifestyle intervention
Metformin in selected patients

If Pregnancy Is Desired

The focus changes.

Treatment may involve:

Ovulation induction
Weight and metabolic management when appropriate
Evaluation of other infertility factors

The exact fertility treatment depends on the individual clinical situation.

Lifestyle Management in PCOS

Lifestyle management can include:

Balanced nutrition
Regular physical activity
Adequate sleep
Weight management when appropriate
Management of metabolic risk factors

Lifestyle treatment should not be framed as “just lose weight.”

PCOS is a complex endocrine and metabolic disorder, and people can have PCOS at different body sizes.

Treatment of Hypothyroidism

If hypothyroidism is responsible for menstrual dysfunction, appropriate thyroid hormone replacement can restore endocrine balance and improve menstrual abnormalities.

Treatment should be guided by laboratory results and clinical assessment.

Treatment of Hyperprolactinemia

Treatment depends on the cause.

For example:

Prolactinoma

May be treated with dopamine agonists such as:

Cabergoline
Bromocriptine

Medication-induced hyperprolactinemia may require:

Medication review
Dose adjustment
Switching medications when appropriate

Treatment of Fibroids

Treatment depends on:

Size
Number
Location
Symptoms
Age
Fertility goals
Severity of bleeding

Options may include:

Medication
LNG-IUS in appropriate patients
Tranexamic acid
Hormonal therapy
Myomectomy
Uterine artery embolization
Other minimally invasive therapies
Hysterectomy

NICE recommends specialist assessment for fibroids 3 cm or larger and emphasizes individualized treatment according to symptoms and patient preferences.

Treatment of Endometrial Polyps

Symptomatic polyps may be removed hysteroscopically.

This can:

Control bleeding
Provide tissue for histological evaluation
Treat the structural lesion directly

Treatment of Adenomyosis

Possible treatments include:

LNG-IUS
Hormonal therapy
NSAIDs for pain
Other medical therapies
Surgical treatment in selected severe cases

Treatment depends on symptom severity and reproductive goals.

Endometrial Ablation

Endometrial ablation destroys or removes much of the endometrial lining.

It may reduce heavy menstrual bleeding in selected patients.

However:

It is not a fertility-preserving treatment.

Pregnancy after endometrial ablation can be dangerous, and the procedure is generally intended for patients who do not desire future pregnancy.

Hysterectomy

Hysterectomy is surgical removal of the uterus.

It:

Permanently stops menstruation
Eliminates the possibility of pregnancy
Can definitively treat uterine causes of abnormal bleeding

Because it is major surgery and eliminates fertility, it is generally reserved for appropriately selected patients after discussion of alternatives.

NICE identifies hysterectomy as one surgical option when symptoms are severe or other treatments are unsuccessful or unsuitable.

Menstrual Irregularities and Fertility

Irregular periods can sometimes indicate:

Irregular ovulation

This can make conception more difficult because ovulation is unpredictable or absent.

Common causes include:

PCOS
Hyperprolactinemia
Thyroid disorders
Hypothalamic dysfunction
Primary ovarian insufficiency

Therefore, irregular periods should not be dismissed when pregnancy is desired.

Primary Ovarian Insufficiency

Primary ovarian insufficiency refers to impaired ovarian function occurring before the expected age of natural menopause.

Possible features include:

Irregular periods
Oligomenorrhea
Amenorrhea
Infertility
Symptoms of estrogen deficiency

ASRM includes hypergonadotropic hypogonadism/ovarian insufficiency among important causes of secondary amenorrhea.

Amenorrhea

Amenorrhea is particularly important because it can have multiple causes.

Primary amenorrhea

Failure to begin menstruation within expected pubertal development.

ASRM recommends evaluation when menstruation has not occurred by age 15 in the presence of normal secondary sexual development, or within 5 years after breast development if breast development began before age 10.

Secondary Amenorrhea

Secondary amenorrhea refers to the absence of menstruation after previously having menstrual cycles.

ASRM defines it as absence of menses for:

More than 3 months in someone who previously had regular cycles
About 6 months in someone whose cycles were previously irregular

Pregnancy must first be excluded.

Causes of Secondary Amenorrhea

A useful framework includes:

Pregnancy

Most important initial consideration.

PCOS

Chronic anovulation.

Hyperprolactinemia

Suppresses reproductive function.

Thyroid disease

Can disturb menstrual regulation.

Hypothalamic dysfunction

Associated with:

Stress
Excessive exercise
Low energy availability

Primary ovarian insufficiency

Reduced ovarian function.

Anatomical abnormalities

Such as intrauterine adhesions.

Intrauterine Adhesions

Also called:

Asherman syndrome

This involves scar tissue within the uterine cavity.

It may occur after:

Uterine procedures
Curettage
Certain infections
Pregnancy-related uterine procedures

It can cause:

Reduced menstrual flow
Amenorrhea
Infertility

ASRM notes that an attenuated endometrial echo in the appropriate clinical context can raise suspicion for endometrial scarring and may warrant further evaluation.

Menstrual Irregularities and Endometrial Hyperplasia

Chronic anovulation can result in prolonged estrogen exposure without adequate cyclic progesterone.

This can cause:

Endometrial proliferation

↓

Endometrial hyperplasia

↓

Potential progression to:

Endometrial intraepithelial neoplasia

↓

Potential progression to:

Endometrial carcinoma

This is particularly relevant in patients with chronic anovulation, including some patients with PCOS.

Why Progestogen Matters

Progesterone or progestogen helps counterbalance estrogenic stimulation of the endometrium.

Therefore, in chronic anovulation, appropriate progestogen exposure may be important for endometrial protection.

This is one reason why prolonged amenorrhea due to chronic anovulation should not simply be ignored.

Menstrual Irregularities and Anemia

Heavy or prolonged bleeding can gradually reduce iron stores.

The sequence may be:

Heavy menstruation

↓

Chronic blood loss

↓

Iron depletion

↓

Iron-deficiency anemia

↓

Symptoms such as:

Fatigue
Weakness
Dizziness
Palpitations
Reduced concentration
Shortness of breath

When Is Menstrual Bleeding an Emergency?

Seek urgent medical attention when heavy bleeding is accompanied by:

Fainting
Severe dizziness
Shortness of breath
Chest pain
Very rapid heartbeat
Extreme weakness
Severe abdominal/pelvic pain
Pregnancy or possible pregnancy
Signs of shock

ACOG advises emergency evaluation when someone is soaking through a pad or tampon approximately every hour for more than two hours and also has symptoms such as chest pain, shortness of breath, lightheadedness, or dizziness.

Practical Clinical Case 1: PCOS

Case

A 22-year-old woman reports periods every 2–3 months.

She also has:

Acne
Increased facial hair
Weight gain

Pregnancy test is negative.

Most likely diagnosis

Polycystic ovary syndrome

Key reasoning

Irregular periods + clinical hyperandrogenism strongly suggest chronic ovulatory dysfunction.

Further assessment should exclude alternative causes and evaluate metabolic health.

Practical Clinical Case 2: Hypothyroidism

A 34-year-old woman develops:

Heavy periods
Fatigue
Weight gain
Cold intolerance
Constipation

Likely consideration

Hypothyroidism

Investigation

TSH ± free T4

Thyroid dysfunction can disrupt normal reproductive hormone function.

Practical Clinical Case 3: Hyperprolactinemia

A 27-year-old woman develops:

Irregular periods
Amenorrhea
Milky nipple discharge

Most likely endocrine cause

Hyperprolactinemia

Investigation

Serum prolactin

If persistently elevated, the cause must be investigated.

Practical Clinical Case 4: Excessive Exercise

A 19-year-old athlete develops amenorrhea after:

Increasing training intensity
Reducing calorie intake
Losing substantial weight

Likely diagnosis

Functional hypothalamic amenorrhea

The key mechanism is suppression of hypothalamic reproductive signaling due to inadequate energy availability.

Practical Clinical Case 5: Fibroid

A 42-year-old woman has:

Very heavy regular periods
Pelvic pressure
Enlarged uterus

Likely cause

Uterine leiomyoma

Investigation

Pelvic ultrasound

Practical Clinical Case 6: Bleeding Disorder

A teenager has had extremely heavy periods since menarche.

She also reports:

Frequent nosebleeds
Easy bruising
Excessive bleeding after dental procedures

Important diagnosis to consider

von Willebrand disease or another bleeding disorder

This is an important clue that the heavy bleeding may not simply be a gynecological problem.

Practical Clinical Case 7: Pregnancy-Related Bleeding

A woman with previously regular periods misses her period and then develops:

Vaginal bleeding
Unilateral pelvic pain
Dizziness

Important emergency diagnosis

Ectopic pregnancy

Pregnancy testing and urgent evaluation are required.

Common Myths About Menstrual Irregularities

Myth 1: “Irregular periods always mean PCOS.”

False.

Other causes include:

Pregnancy
Thyroid disease
Hyperprolactinemia
Hypothalamic dysfunction
Primary ovarian insufficiency
Structural disease
Medications

Myth 2: “Stress is always the cause.”

False.

Stress can affect menstrual function, but persistent irregularity requires appropriate assessment.

Myth 3: “Heavy periods are normal if they have always been heavy.”

Not necessarily.

Heavy bleeding from menarche can be a clue to a bleeding disorder.

Myth 4: “PCOS means ovarian cysts must be present.”

False.

Polycystic ovarian morphology is not required in every patient with PCOS.

Myth 5: “A missed period always means pregnancy.”

Pregnancy is an important first consideration, but other causes include:

PCOS
Thyroid disease
Hyperprolactinemia
Hypothalamic dysfunction
Ovarian insufficiency

Myth 6: “Menstrual irregularity is just a cosmetic issue.”

False.

Persistent abnormalities can be associated with:

Infertility
Anemia
Endometrial hyperplasia
Metabolic disease
Reduced quality of life
Underlying endocrine disorders

WHO emphasizes that significant menstrual symptoms can affect education, work, relationships, social participation, and overall quality of life.

Prevention and Menstrual Health

Not every cause can be prevented, but several measures can support menstrual health.

Maintain adequate nutrition

Avoid extreme calorie restriction.

Exercise appropriately

Regular physical activity is beneficial, but excessive training combined with inadequate energy intake can disrupt menstruation.

Monitor menstrual patterns

Track:

Dates
Duration
Flow
Pain
Spotting

Seek evaluation for persistent abnormalities

Especially when cycles suddenly change.

Treat chronic conditions

Examples:

PCOS
Thyroid disease
Diabetes
Bleeding disorders

Review medications

Particularly hormonal medications and anticoagulants.

Menstrual Irregularities: Clinical Approach

A practical approach is:

Step 1

Determine the bleeding pattern.

Too frequent?

Too infrequent?

Too heavy?

Too prolonged?

Intermenstrual?

Postcoital?

Absent?

↓

Step 2

Exclude pregnancy when relevant.

↓

Step 3

Look for emergency features.

Hemodynamic instability?

Severe pain?

Possible ectopic pregnancy?

↓

Step 4

Assess likely cause.

Think:

PALM-COEIN

↓

Step 5

Perform targeted laboratory testing.

↓

Step 6

Use ultrasound/hysteroscopy/endometrial assessment when indicated.

↓

Step 7

Treat the cause.

↓

Step 8

Monitor response and recurrence.

Quick Comparison of Major Causes

Cause	Typical clues
PCOS	Irregular cycles + hyperandrogenism
Hypothyroidism	Fatigue, weight gain, cold intolerance
Hyperprolactinemia	Amenorrhea + galactorrhea
Pregnancy	Missed period
Ectopic pregnancy	Pregnancy + pain + bleeding
Fibroid	Heavy bleeding + pressure/enlarged uterus
Adenomyosis	Heavy painful periods + bulky tender uterus
Polyp	Intermenstrual/postcoital bleeding
Bleeding disorder	Heavy bleeding since menarche + bruising
Hypothalamic dysfunction	Low weight/excess exercise/stress
Primary ovarian insufficiency	Amenorrhea/irregular cycles + ovarian insufficiency
Perimenopause	Increasing cycle variability in later reproductive years
Endometrial malignancy	Persistent abnormal bleeding, particularly with risk factors

High-Yield Pharmacology

Drug	Main role
Tranexamic acid	Reduces menstrual blood loss
NSAIDs	Reduce bleeding and menstrual pain in selected patients
Combined hormonal contraception	Cycle control + contraception
Progestogens	Endometrial protection and cycle control
LNG-IUS	Major option for heavy menstrual bleeding
Metformin	Used in selected patients with PCOS/metabolic features
Levothyroxine	Treats hypothyroidism
Cabergoline	Treats many cases of hyperprolactinemia/prolactinoma
Iron	Treats iron deficiency/iron-deficiency anemia

High-Yield Examination Points

Point 1

Normal adult menstrual cycles are commonly around:

21–35 days

Point 2

A typical period lasts:

Up to about 7 days

Point 3

The two major hormones regulating the endometrium are:

Estrogen + progesterone

Point 4

Ovulation is triggered by:

LH surge

Point 5

The corpus luteum primarily produces:

Progesterone

Point 6

A common cause of irregular periods is:

Ovulatory dysfunction

Point 7

A major cause of chronic anovulation is:

PCOS

Point 8

A first consideration in secondary amenorrhea is:

Pregnancy

Point 9

Important tests in amenorrhea include:

Pregnancy test + TSH + prolactin + FSH/E2 as appropriate

Point 10

Heavy menstrual bleeding may cause:

Iron-deficiency anemia

Point 11

Heavy bleeding from menarche plus easy bruising suggests:

Bleeding disorder

Point 12

The PALM causes are:

Polyp, Adenomyosis, Leiomyoma, Malignancy/hyperplasia

Point 13

COEIN stands for:

Coagulopathy, Ovulatory dysfunction, Endometrial, Iatrogenic, Not otherwise classified

Point 14

PCOS is associated with:

Hyperandrogenism + ovulatory dysfunction

Point 15

Postmenopausal bleeding requires:

Evaluation

Frequently Asked Questions

1. What is the most common cause of irregular periods?

There is no single cause for all patients. Ovulatory dysfunction, particularly PCOS, is a major cause, but pregnancy, thyroid disorders, hyperprolactinemia, lifestyle factors, medications, and structural uterine disease are also important.

2. Are irregular periods always dangerous?

No.

Irregular cycles can occur normally during adolescence and perimenopause.

However, persistent, severe, new, or symptomatic abnormalities should be evaluated.

3. Can PCOS cause irregular periods?

Yes.

PCOS commonly causes irregular or absent periods because of ovulatory dysfunction. WHO identifies PCOS as a major cause of irregular menstruation and anovulation.

4. Can thyroid problems cause irregular periods?

Yes.

Both hypothyroidism and hyperthyroidism can interfere with normal menstrual function.

5. Can stress delay menstruation?

Yes.

Significant psychological or physiological stress can affect hypothalamic reproductive signaling.

But persistent amenorrhea should not automatically be attributed to stress.

6. Can excessive exercise stop periods?

Yes.

Excessive exercise combined with inadequate energy availability can suppress reproductive hormone signaling and cause amenorrhea.

7. Can being underweight cause irregular periods?

Yes.

Low energy availability and reduced body fat can interfere with hypothalamic-pituitary-ovarian function.

8. Can obesity cause irregular periods?

Yes.

Obesity can be associated with ovulatory dysfunction and is frequently associated with PCOS and other endocrine abnormalities.

9. Can irregular periods cause infertility?

They can.

Irregular menstruation often reflects irregular ovulation, which can make conception more difficult.

10. Can heavy periods cause anemia?

Yes.

Repeated blood loss can lead to iron deficiency and iron-deficiency anemia.

11. Is bleeding for more than seven days normal?

Bleeding that consistently lasts more than seven days should be evaluated, particularly when it is heavy or affects quality of life. ACOG and NICE both recognize prolonged heavy bleeding as clinically significant.

12. When should I worry about heavy bleeding?

Seek urgent medical attention when very heavy bleeding is accompanied by:

Dizziness
Fainting
Shortness of breath
Chest pain
Severe weakness
Rapid heartbeat
Severe pain

13. What test should be done first when a period is missed?

When pregnancy is possible:

Pregnancy testing

should be the first consideration.

ASRM specifically emphasizes excluding pregnancy first in secondary amenorrhea.

14. Does every patient with irregular periods need an ultrasound?

No.

Ultrasound is selected according to the clinical presentation and suspected cause.

For example, it is particularly useful when structural disease such as fibroids or adenomyosis is suspected.

15. Does every patient with heavy bleeding need hormone tests?

No.

For example, NICE does not recommend routine female hormone testing solely for heavy menstrual bleeding.

Testing should be guided by the suspected cause.

16. Can hormonal contraception cause spotting?

Yes.

Breakthrough or irregular bleeding can occur with hormonal contraception.

17. Can a copper IUD make periods heavier?

Yes.

Copper IUDs can increase menstrual bleeding, especially during the first year.

18. Can menstrual irregularity be a sign of cancer?

Sometimes.

Most irregular bleeding is not caused by cancer, but persistent abnormal bleeding—particularly in higher-risk patients or after menopause—requires appropriate evaluation.

Final Summary

Menstrual irregularities are a symptom, not a single disease.

A normal menstrual cycle depends on coordinated function of:

Hypothalamus → Pituitary → Ovary → Endometrium

Disruption anywhere along this pathway can alter menstruation.

Common manifestations include:

Irregular periods
Heavy bleeding
Prolonged bleeding
Intermenstrual bleeding
Amenorrhea
Oligomenorrhea
Spotting
Sudden changes in previously regular cycles

Major causes include:

PCOS

Pregnancy

Thyroid disease

Hyperprolactinemia

Hypothalamic dysfunction

Primary ovarian insufficiency

Fibroids

Polyps

Adenomyosis

Bleeding disorders

Medications

Endometrial pathology

A useful framework for abnormal uterine bleeding is:

PALM-COEIN

PALM = structural causes

Polyp
Adenomyosis
Leiomyoma
Malignancy/hyperplasia

COEIN = nonstructural causes

Coagulopathy
Ovulatory dysfunction
Endometrial
Iatrogenic
Not otherwise classified

Diagnosis should be individualized.

Important initial considerations include:

Pregnancy test → menstrual history → physical examination → targeted laboratory testing → imaging/endometrial evaluation when indicated

Treatment depends on the underlying cause and may include:

Lifestyle intervention
Iron therapy
Hormonal therapy
Tranexamic acid
NSAIDs
LNG-IUS
PCOS treatment
Thyroid treatment
Prolactin-directed therapy
Fibroid/polyp treatment
Endometrial procedures
Surgery

The most important clinical principle is:

Do not simply try to make the menstrual cycle “regular” without finding out why it became irregular.

A missed period may be pregnancy.
Irregular periods may be PCOS.
Heavy bleeding may be fibroids or a bleeding disorder.
Amenorrhea may indicate hypothalamic dysfunction or ovarian insufficiency.
Bleeding after menopause may indicate endometrial pathology.

Therefore, the pattern of menstrual abnormality provides important diagnostic information.