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OG25.1 | Amenorrhea — SDL Guide

Learning Objectives

• Define primary and secondary amenorrhea with the correct age and duration thresholds
• Classify the causes of amenorrhea using a compartment-based framework (outflow/uterine, ovarian, pituitary, hypothalamic)
• Describe the clinical features and hormonal patterns that distinguish major causes within each compartment
• Outline a systematic investigation approach including β-hCG, TSH, prolactin, FSH/LH, progesterone challenge, karyotype, and pelvic ultrasound
• Discuss the principles of management tailored to each aetiology, including fertility implications and long-term considerations

INSTRUCTIONS

Amenorrhea — the absence of menstruation — is one of the most common and diagnostically rich presentations in gynaecological practice. Far from being a single diagnosis, it is a symptom whose cause can reside at any level of the hypothalamic-pituitary-ovarian-uterine axis. This module guides you through a structured compartment-based framework to localise the problem, interpret investigations logically, and apply cause-specific management. The skills you develop here — systematic hormonal thinking and pattern recognition — underpin your ability to counsel patients effectively on fertility, long-term bone health, and cardiovascular risk.

References

• DC Dutta's Textbook of Gynaecology, 8th ed., Ch. 24 — Amenorrhea (textbook)
• Shaw's Textbook of Gynaecology, 17th ed., Ch. 19 — Amenorrhea and Oligomenorrhea (textbook)
• Jeffcoate's Principles of Gynaecology, 8th ed., Ch. 22 (textbook)
• ESHRE Guideline: Management of women with premature ovarian insufficiency, 2016 (guideline)
• Endocrine Society Clinical Practice Guideline: Functional Hypothalamic Amenorrhea, 2017 (guideline)

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Version 2.0 | NMC CBUC 2024

Clinical Presentation and Classification of Amenorrhea

Amenorrhea is defined not merely as the absence of menstruation, but with specific age- and duration-based thresholds that reflect clinically actionable cut-points. Understanding which definition applies is the first step in the clinical encounter.

Primary amenorrhea is the condition in which menstruation has never occurred. The two accepted thresholds are: no menarche by the age of 15 years when secondary sexual characteristics (thelarche, pubarche) are present, and no menarche by the age of 13 years when there are no secondary sexual characteristics whatsoever. The logic behind the lower threshold is that the absence of secondary sexual characteristics at 13 suggests a more fundamental failure of puberty — likely at the ovarian or hypothalamic-pituitary level — and warrants earlier evaluation. Using the higher cut-off when secondary sexual characteristics are present acknowledges that most adolescents with breast development who have not yet menstruated by 15 will have a structural anomaly of the outflow tract rather than a failure of hormonal activation.

Secondary amenorrhea is defined as the cessation of previously established menses. The conventional duration thresholds are: absence of ≥3 months in a woman who previously had regular monthly cycles, or ≥6 months in a woman who previously had irregular cycles. The rationale for the longer threshold in irregular-cycle patients is that occasional gaps are expected in anovulatory states such as polycystic ovary syndrome (PCOS), and labelling a 3-month gap as secondary amenorrhea would over-medicalise normal variation. Pregnancy must always be excluded before either category of amenorrhea is further investigated — a serum β-hCG is the mandatory first step.

The clinical evaluation begins with a careful history: when did periods start (if ever), how regular were they, was there a precipitating event (weight change, intense exercise, stress, uterine procedure, postpartum haemorrhage, systemic illness), are there symptoms of hypoestrogenism (hot flushes, vaginal dryness, dyspareunia), galactorrhoea (suggests hyperprolactinaemia), or hirsutism and acne (suggests androgen excess). The presence or absence of secondary sexual characteristics on examination directs the initial compartment hypothesis. A normal height and normal sexual development in primary amenorrhea suggests an intact hormonal axis with a structural outflow or uterine problem, while short stature with absent sexual development points strongly toward a chromosomal or gonadal cause.

Compartment-Based Causes of Amenorrhea in the HPO Axis

Physiological Basis and Compartment-Based Aetiology

The most powerful organising principle for amenorrhea is the compartment-based aetiology framework, which asks: at which level of the reproductive axis has the menstrual process been disrupted? There are four compartments, each with a distinct hormonal signature that allows you to localise the problem with targeted blood tests before any definitive imaging. The value of this framework lies in its parsimony: rather than memorising an undifferentiated list of 20-plus diagnoses, you learn four hormonal archetypes and then populate each with its specific conditions. This approach transforms the investigation of amenorrhea from a scatter-gun hormone panel into a directed, logical sequence that conserves resources and minimises patient anxiety.

The four compartments correspond to the four anatomical levels where the menstrual process can be disrupted: (1) the hypothalamus, which generates the GnRH pulse; (2) the anterior pituitary, which converts that pulse into FSH and LH; (3) the ovary, which responds to FSH and LH by developing a follicle and producing oestradiol; and (4) the outflow tract and uterus, which responds to ovarian hormones by growing and shedding the endometrium. Because each level depends on the one above it, a lesion at any level creates a characteristic upstream-downstream hormonal pattern. Specifically: a failure at the ovary will deprive the pituitary of negative feedback, causing FSH and LH to rise — creating the hypergonadotrophic pattern. A failure at the hypothalamus or pituitary will deprive the ovary of its stimulatory signal, causing FSH and LH to fall — the hypogonadotrophic pattern. And a failure at the uterus or outflow tract does not alter the hormonal axis at all — the hormones are entirely normal, but the end-organ cannot respond or the menstrual flow cannot exit.

The four compartments and their characteristic hormonal patterns:

Compartment	Key Causes	FSH	LH	Oestradiol	Prolactin
Hypothalamic	FHA, craniopharyngioma, Kallmann	Low	Low	Low	Normal/low
Pituitary	Prolactinoma, Sheehan, empty sella	Low/normal	Low/normal	Low	Elevated (prolactinoma)
Ovarian	Turner, POI, PCOS	Elevated (POI/Turner) / Normal (PCOS)	Elevated / Elevated LH (PCOS)	Low (POI/Turner) / Variable (PCOS)	Normal
Outflow/Uterine	MRKH, Asherman, imperforate hymen	Normal	Normal	Normal	Normal

The key insight is that if the ovaries have failed (compartment III), the pituitary loses inhibitory feedback from oestradiol and drives FSH and LH upward — this is called hypergonadotrophic hypogonadism. If the problem is above the ovary (hypothalamus or pituitary), the signal to the ovary is absent and FSH/LH are inappropriately low — hypogonadotrophic hypogonadism. If the ovaries are functioning normally but the uterus or outflow is obstructed, the hormonal axis is intact and FSH/LH/oestradiol are all normal — the classic normogonadotrophic pattern. PCOS represents a distinct normogonadotrophic picture with anovulation and hyperandrogenism. This hormonal classification allows you to direct the investigation toward the correct compartment before committing to expensive imaging.

Outflow Tract and Uterine Causes

Outflow tract and uterine causes produce primary or secondary amenorrhea in the presence of a hormonally normal axis. Because the ovaries are intact and producing oestradiol, the patient has normal secondary sexual development — the hallmark of this compartment.

Müllerian agenesis (MRKH syndrome — Mayer-Rokitansky-Küster-Hauser) is the commonest structural cause of primary amenorrhea, accounting for approximately 15% of cases. The karyotype is 46XX (a normal female genotype), the ovaries are present and functional, and secondary sexual characteristics are completely normal. The defect is developmental failure of the Müllerian (paramesonephric) ducts, resulting in absence of the uterus and the upper two-thirds of the vagina. On examination, there is a short blind vaginal pouch. The FSH, LH, and oestradiol are all normal. MRKH must be distinguished from complete androgen insensitivity syndrome (CAIS), which also presents with primary amenorrhea, absent uterus, and normal female external genitalia — but the karyotype is 46XY, and serum testosterone is in the male range (because the patient has undescended testes producing testosterone that cannot be utilised at androgen receptors). Karyotype testing is therefore mandatory in every patient with primary amenorrhea and absent uterus.

Provided image

Asherman syndrome (intrauterine adhesions, synechiae) is the commonest cause of secondary amenorrhea in the uterine compartment. It results from destruction of the basal endometrial layer, most often after dilatation and curettage (D&C) — particularly post-pregnancy curettage (for incomplete abortion, missed abortion, or postpartum retained products) where the decidualised endometrium is especially vulnerable. In India, endometrial tuberculosis is an important additional cause. The hallmark finding is that the progesterone challenge test produces no withdrawal bleed, because even if oestrogen primes the endometrium, adhesions prevent it from shedding normally. Hysteroscopy is both diagnostic (directly visualises adhesions) and the definitive treatment modality.

Other outflow tract causes include imperforate hymen (typically presents at menarche with cyclical lower abdominal pain, haematocolpos, bulging membrane at the introitus — classified as obstructive primary amenorrhea with cyclic pain rather than true hormonal amenorrhea), transverse vaginal septum, and cervical stenosis (post-cone biopsy or post-D&C).