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Here is a thorough, structured overview of menstrual cycle disturbances - identification and investigation.
Menstrual Cycle Disturbances: Identification and Investigation
Normal Cycle - Reference Point
A normal menstrual cycle is 21-35 days long, with bleeding lasting 2-7 days and blood loss of 20-80 mL. Ovulation normally occurs around day 14 in a 28-day cycle. The hormonal interplay is shown below:
Classification of Menstrual Disturbances
| Term | Definition |
|---|---|
| Primary amenorrhea | No menses by age 15 with secondary sexual characteristics, or age 13 without |
| Secondary amenorrhea | Absence of menses for 3 cycles or 3 months in a previously menstruating woman |
| Oligomenorrhea | Fewer than 9 cycles/year, or cycle length >35 days |
| Menorrhagia | Heavy or prolonged menstrual bleeding |
| Dysmenorrhea | Painful menstruation |
| Metrorrhagia | Irregular bleeding between periods |
A woman with regular cycles and even a week's delay warrants a pregnancy test. Evaluation is advisable if a woman has fewer than 9 cycles per year or cycle length longer than 35 days. (Berek & Novak's Gynecology)
WHO Classification of Amenorrhea
The World Health Organization classifies amenorrhea into three groups, plus a fourth added later:
- WHO Group I - Hypogonadotropic hypogonadism: no endogenous estrogen, normal/low FSH, normal prolactin, no hypothalamic-pituitary lesion
- WHO Group II - Normogonadotropic anovulation (e.g. PCOS): evidence of estrogen production, normal FSH and prolactin
- WHO Group III - Hypergonadotropic hypogonadism: elevated FSH indicating gonadal failure (e.g. premature ovarian insufficiency)
- WHO Group IV (added later) - Hyperprolactinemic anovulation: anovulation due specifically to elevated prolactin
(Berek & Novak's Gynecology, Tietz Textbook of Laboratory Medicine 7e)
Common Causes
Hypothalamic / Functional
- Excessive exercise, stress, nutritional disorders, weight loss
- Hypothalamic tumors or infiltrative disease
- Functional hypothalamic amenorrhea (HPO axis suppression)
Pituitary
- Hyperprolactinemia (prolactinoma, drug-induced) - presents with galactorrhea + oligomenorrhea/amenorrhea
- Sheehan syndrome (postpartum pituitary necrosis)
- Pituitary apoplexy, empty sella syndrome
- Acquired hypopituitarism (trauma, tumor)
Ovarian
- PCOS (most common cause of oligomenorrhea) - hyperandrogenism + oligo/amenorrhea + polycystic ovaries (Rotterdam criteria: 2 of 3 required)
- Premature Ovarian Insufficiency (POI) - ovarian failure before age 40, hypergonadotropic state
- Gonadal dysgenesis (Turner syndrome 45,X - most common in primary amenorrhea)
- Autoimmune oophoritis
Uterine / Outflow Tract
- Asherman syndrome - intrauterine adhesions from D&C or infection; normal hormones but no bleeding
- Endometrial damage, cervical stenosis
Endocrine / Systemic
- Thyroid disease (hypothyroidism or hyperthyroidism)
- Congenital adrenal hyperplasia (21-hydroxylase deficiency most common)
- Cushing syndrome
- Chronic disease, cancer
Drugs / Iatrogenic
- Antipsychotics (phenothiazines, haloperidol, clozapine) - cause hyperprolactinemia
- Antidepressants (tricyclics, MAOIs)
- Antihypertensives (methyldopa, calcium channel blockers, reserpine)
- Drugs with estrogenic activity (digitalis, marijuana, oral contraceptives)
- Cytotoxic chemotherapy (busulfan, cyclophosphamide, cisplatin)
Physiological
- Pregnancy (most common cause of secondary amenorrhea)
- Lactation
- Perimenopause
Investigation Algorithm
Step 1: History
- Complete menstrual history (age at menarche, cycle regularity, flow, pain)
- Galactorrhea, hot flashes, hirsutism, acne
- Symptoms of hypothyroidism
- Weight changes, exercise habits, nutritional status, stress
- Prior pelvic surgery or trauma, infections (PID)
- Current medications
- Contraceptive history
Step 2: Physical Examination
- BMI, weight, signs of androgen excess (hirsutism, acne, virilization)
- Thyroid palpation
- Breast examination (galactorrhea)
- Visual fields (pituitary tumor may cause bitemporal hemianopia)
- Pelvic examination (uterus, ovaries, outflow tract)
- Secondary sexual characteristics (absent in Turner syndrome)
Step 3: First-Line Laboratory Tests
| Test | What it detects |
|---|---|
| Urine/serum hCG | Pregnancy (always first) |
| FSH + LH | Ovarian reserve; elevated = ovarian failure; low/normal = hypothalamic/pituitary cause |
| Prolactin | Hyperprolactinemia (prolactinoma, drug-induced) |
| TSH | Thyroid dysfunction |
| Total testosterone + androstenedione | Hyperandrogenism (PCOS, adrenal, tumor) |
| DHEA-S | Adrenal androgen excess; very high = adrenal tumor |
| 17-hydroxyprogesterone | Congenital adrenal hyperplasia (21-hydroxylase deficiency) |
| AMH (Anti-Mullerian Hormone) | Ovarian reserve; elevated in PCOS, very low in POI |
Note on androgen testing: Androstenedione has better sensitivity (88.3%) and specificity (97.7%) for detecting androgen excess in PCOS than testosterone alone. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is preferred over immunoassay for androgen measurement in women due to the low concentrations involved. (Tietz Textbook of Laboratory Medicine 7e)
Note on PCOS diagnosis: Serum AMH >35 pmol/L (5 ng/mL) has been proposed as a surrogate for polycystic ovarian morphology, but the 2018 International PCOS Network recommends against using AMH alone as a standalone diagnostic test. (Tietz Textbook of Laboratory Medicine 7e)
Step 4: Imaging
- Pelvic ultrasound - uterine structure, endometrial thickness, ovarian morphology (polycystic ovaries), follicle count
- MRI pituitary - if prolactin elevated or pituitary tumor suspected
Step 5: Additional / Targeted Tests
| Situation | Additional test |
|---|---|
| Elevated FSH, age <25 or short stature | Karyotype / chromosomal microarray (rule out Turner syndrome, Y chromosome) |
| Elevated FSH, POI | FMR1 premutation screening (fragile X) |
| Elevated FSH, POI | Autoimmune antibodies (adrenal, thyroid, ovarian) |
| Suspected Asherman syndrome | Hysteroscopy or sonohysterogram |
| Virilization | DHEA-S, pelvic/adrenal imaging (rule out tumor) |
| Suspected CAH | 17-hydroxyprogesterone, ACTH stimulation test |
| Cushing suspected | 24-hour urinary free cortisol, dexamethasone suppression |
Key Diagnostic Points
- Pregnancy must always be excluded first before any other workup.
- Oligomenorrhea etiologies largely overlap with amenorrhea; the distinction between primary and secondary amenorrhea should not be overemphasized clinically. (Berek & Novak's Gynecology)
- In PCOS, the LH:FSH ratio is often elevated, but this ratio should not be used as a routine diagnostic test.
- Women with POI younger than 25 or shorter than 5 feet should have karyotyping to rule out chromosomal abnormalities, including a Y chromosome (gonadoblastoma risk).
- Asherman syndrome presents with normal hormones but absent menses - the outflow tract is structurally blocked.
Sources: Berek & Novak's Gynecology; Tietz Textbook of Laboratory Medicine 7e; Textbook of Family Medicine 9e; Goldman-Cecil Medicine.
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