Secondary Amenorrhoea (Hyperprolactinaemia)
A 26-year-old woman presents with eight months of absent periods after previously regular cycles. She reports bilateral milky nipple discharge and reduced libido but no headache or visual disturbance. She takes no medication. A urine pregnancy test is negative, and pelvic examination and body mass index are normal. Which of the following is the most appropriate initial investigation?
- A.Magnetic resonance imaging of the brain
- B.Karyotype analysis
- C.Hysteroscopy
- D.Serum prolactin levelCorrect
Explanation
Secondary amenorrhoea with galactorrhoea in a young woman points to hyperprolactinaemia, and once pregnancy is excluded the first step is simply to measure the serum prolactin. Prolactin suppresses pulsatile gonadotrophin-releasing hormone secretion, which lowers luteinising and follicle-stimulating hormone and stops ovulation, producing oligomenorrhoea or amenorrhoea, infertility, reduced libido and, with prolonged oestrogen deficiency, bone loss. Thyroid-stimulating hormone is checked at the same time because primary hypothyroidism raises prolactin, and a careful drug history matters since antipsychotics, metoclopramide and some antidepressants are frequent causes. Only after a genuinely and persistently elevated level is confirmed does pituitary imaging become indicated, to separate a microprolactinoma from a macroadenoma or a stalk-compressing lesion; imaging first is costly and may reveal incidental findings that mislead. Karyotyping belongs to primary amenorrhoea and premature ovarian insufficiency, neither suggested by eight months of secondary amenorrhoea with galactorrhoea. Hysteroscopy investigates intrauterine adhesions after uterine instrumentation and would not explain galactorrhoea. A dopamine agonist is the usual treatment once a prolactinoma is confirmed.
Why each option
- A.
- Pituitary imaging follows a confirmed elevated prolactin level rather than preceding it, and may otherwise reveal misleading incidental findings.
- B.
- Karyotype analysis is used for primary amenorrhoea or premature ovarian insufficiency, not for galactorrhoea with secondary amenorrhoea.
- C.
- Hysteroscopy assesses intrauterine adhesions after uterine instrumentation and cannot explain galactorrhoea.
- D.
- Correct. Measuring serum prolactin confirms the hyperprolactinaemia that explains both the galactorrhoea and the amenorrhoea before any imaging is arranged.
Reference: Endocrine Society, Clinical Practice Guideline: Diagnosis and Treatment of Hyperprolactinemia, 2011.
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