Describe amenorrhoea — its aetiology, clinical features and management.

Definition

Amenorrhoea is the absence of menstruation. Primary amenorrhoea — failure to menstruate by 15 years with normal secondary sexual characteristics (or by 13 years in their absence). Secondary amenorrhoea — cessation of menstruation for 6 months (or three cycles) in a woman who previously menstruated.

Physiological Causes

Before puberty, during pregnancy and lactation, and after the menopause.

Pathological Causes (BY Level)

• Outflow tract/uterus — imperforate hymen, transverse vaginal septum, Müllerian agenesis (Rokitansky), and Asherman's syndrome (intra-uterine adhesions).
• Ovary — gonadal dysgenesis (Turner's syndrome), premature ovarian failure and PCOS.
• Pituitary — prolactinoma/hyperprolactinaemia and Sheehan's syndrome.
• Hypothalamus — stress, excessive exercise, weight loss/anorexia, and chronic illness.

Investigations

A pregnancy test first, then serum FSH/LH, prolactin and TSH, a progesterone challenge, and ultrasound/karyotype as indicated to localise the cause.

Management (principle)

Treatment is directed at the cause — relieving an outflow obstruction (e.g. Cruciate incision of an imperforate hymen), dopamine agonists for hyperprolactinaemia, ovulation induction or cyclical oestrogen-progestogen for ovarian/hypothalamic causes, and hormone replacement in premature ovarian failure or gonadal dysgenesis.

A Note on WHY Amenorrhoea Is Approached 'from the Bottom Up'

A useful concept is understanding why the causes of amenorrhoea are best approached anatomically, working upwards from the outflow tract to the brain — which turns a bewildering list into an orderly investigation. Menstruation requires four things, in ascending order: a patent outflow tract; a responsive endometrium; functioning ovaries producing oestrogen and progesterone; and an intact hypothalamic-pituitary axis to drive them. Failure at any level stops the periods. Hence the compartments: outflow (imperforate hymen, transverse vaginal septum, cervical stenosis — causing cryptomenorrhoea, in which menstruation occurs but cannot escape, giving cyclical pain and a haematocolpos); uterine/endometrial (Asherman's syndrome — intrauterine adhesions after over-vigorous curettage or genital TB; Mullerian agenesis); ovarian (premature ovarian insufficiency, PCOS, gonadal dysgenesis such as Turner's); and hypothalamic-pituitary (stress, weight loss, excessive exercise, hyperprolactinaemia, Sheehan's syndrome, tumours). This scheme dictates the tests: first exclude pregnancy (always), then measure FSH/LH (high = ovarian failure; low = hypothalamic-pituitary), prolactin and TSH, and use a progestogen challenge to test for oestrogen and a patent tract.

Exclude pregnancy before any other investigation.

• Always exclude pregnancy first — it is by far the commonest cause of secondary amenorrhoea.
• Primary amenorrhoea: no menses by 15 years (with secondary sexual characters) or by 13 (without); secondary: cessation for 6 months (or 3 cycles).
• Approach by compartment: outflow tract (imperforate hymen → cryptomenorrhoea), uterus (Asherman's, TB, Mullerian agenesis), ovary (POI, PCOS, Turner's), hypothalamic-pituitary (stress, weight loss, exercise, prolactinoma, Sheehan's).
• Investigate: pregnancy test, FSH/LH (high = ovarian failure; low = hypothalamic-pituitary), prolactin, TSH, ultrasound, karyotype if primary.
• Treat the cause: hormone replacement in ovarian failure, dopamine agonist for hyperprolactinaemia, weight restoration, surgery for outflow obstruction.

A further point is that cryptomenorrhoea deserves special mention: the girl menstruates normally but the blood cannot escape (most often because of an imperforate hymen), so she presents with primary amenorrhoea accompanied by cyclical lower abdominal pain, a lower abdominal mass and a tense, bulging bluish membrane at the introitus — and is cured completely by a simple cruciate incision (hymenotomy), which makes it the one cause of amenorrhoea that must never be missed on examination.