Amenorrhoea Causes

Overview – Amenorrhoea Causes

Amenorrhoea is the absence of menstruation in a woman of reproductive age and is a common clinical presentation with a range of potential causes. Differentials include hormonal contraceptive use, physiological states like pregnancy, pathological conditions such as hypothalamic suppression and premature menopause. Accurate identification of the underlying cause is essential for effective management and fertility planning.

Definition

Amenorrhoea is defined as the absence of a menstrual period in a woman of reproductive age. It may be primary (never initiated menstruation) or secondary (cessation of previously regular cycles).

Hormonal Contraceptives

Aetiology

• Prolonged or recent use of hormonal contraception:
  • Depo-Provera (injectable)
  • Progesterone-only pills or implants (e.g. Implanon, Mirena)
  • Combined oral contraceptive pills (COCP) – especially with extended-cycle use (skipping sugar pills)

Pathogenesis

• Depo-Provera can suppress ovulation for several months beyond cessation
• Extended-cycle COCP use → constant high levels of oestrogen and progesterone → inhibits withdrawal bleed
• Progesterone-only contraceptives commonly cause menstrual irregularity, prolonged amenorrhoea, or erratic bleeding

Hypothalamic Amenorrhoea (Anorexia / Female Athlete Triad)

Aetiology

• Functional hypothalamic suppression due to:
  • Anorexia nervosa
  • Excessive exercise
  • Female athlete triad (low energy availability, menstrual dysfunction, osteoporosis)

Pathogenesis

• Inadequate energy intake/excessive energy expenditure → impaired hypothalamic GnRH secretion
  → ↓ FSH & LH
  → anovulation → amenorrhoea

Clinical Features

• Low BMI
• History of intense training or eating disorders
• Symptoms of female athlete triad (fatigue, amenorrhoea, bone loss)

Management

• Nutritional rehabilitation
• Moderate exercise routines
• Psychological support and treatment for eating disorders

Physiological Amenorrhoea (Pregnancy & Lactation)

Aetiology

• Pregnancy
• Breastfeeding

Mechanism

• Pregnancy:
  • ↑ β-hCG mimics LH → sustains corpus luteum → high progesterone → inhibits endometrial shedding
• Lactation:
  • Prolactin (stimulated by suckling) → inhibits GnRH secretion
    → ↓ FSH & LH → anovulation and amenorrhoea

Premature Menopause (Premature Ovarian Insufficiency)

Aetiology

• Idiopathic
• Autoimmune oophoritis
• Chemotherapy/radiotherapy
• Surgical oophorectomy

Pathogenesis

• Premature depletion of ovarian follicles → ↓ oestrogen
  → Loss of negative feedback → ↑ GnRH, ↑ FSH
  → Amenorrhoea

Clinical Features

• Menopausal symptoms:
  • Hot flushes
  • Mood changes
  • Vaginal dryness
  • Dry skin
• Complications:
  • ↑ Risk of osteoporosis

Management

• Hormone Replacement Therapy (HRT)
  • Combined oestrogen and progesterone therapy (if uterus intact)
  • Aim to alleviate symptoms and reduce long-term complications

Summary – Amenorrhoea Causes

Amenorrhoea can be physiological (pregnancy, lactation), medication-induced (hormonal contraceptives), or pathological (hypothalamic suppression, premature menopause). Identifying the underlying cause is essential for guiding investigations and management. For a broader context, see our Reproductive Health Overview page.