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Hyperprolactinaemia endocrine effects — MRCPsych Paper A MCQ

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ModerateNeuroimaging, neuroendocrinology and psychoneuroimmunologyHyperprolactinaemia endocrine effectsMRCPsych Paper A

A 27-year-old woman treated with risperidone develops secondary amenorrhoea and difficulty conceiving. Investigations show raised serum prolactin, low oestradiol and low-normal luteinising hormone and follicle-stimulating hormone concentrations. Which mechanism best explains these findings?

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Correct answer: B — Prolactin suppresses pulsatile GnRH release, reducing LH and FSH secretion

Explanation lettering: E = shown as A · D = shown as C · A = shown as D · C = shown as E

The correct answer is B. Risperidone antagonises dopamine D2 receptors in the tuberoinfundibular pathway, removing dopaminergic inhibition of pituitary prolactin secretion. Raised prolactin suppresses hypothalamic GnRH pulsatility, reducing LH and FSH secretion and consequently ovarian oestradiol production. This produces hypogonadotropic hypogonadism, with amenorrhoea, anovulation and impaired fertility. Prolactin does not cause continuous GnRH stimulation and receptor downregulation (A). Direct ovarian D2 antagonism is not the principal mechanism (C). Increased inhibin would predominantly suppress FSH and does not explain this established hyperprolactinaemic pathway (D). Risperidone blocks dopamine receptors rather than increasing hypothalamic dopamine release (E).

Reference: Electronic Medicines Compendium. Risperidone 1 mg/ml oral solution, Summary of Product Characteristics, sections 4.6 and 4.8. Updated 14 July 2026. https://www.medicines.org.uk/emc/product/4364/smpc