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Persistent Hyperprolactinaemia — MRCPsych Paper B MCQ

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HardSchizophrenia & PsychosisPersistent HyperprolactinaemiaMRCPsych Paper B

A 42-year-old man with schizophrenia developed gynaecomastia while taking oral risperidone 6 mg daily. His serum prolactin was 3200 mIU/L. Risperidone was discontinued, and he has now taken aripiprazole monotherapy for 12 weeks. Two appropriately collected morning samples show prolactin concentrations of 2750 and 2800 mIU/L. Macroprolactin has been excluded, and thyroid and renal function are normal. He takes no other prolactin-raising medication. What is the most appropriate next step?

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Reveal the answer and explanation

Correct answer: C — Refer to endocrinology and arrange pituitary MRI to investigate for a prolactinoma

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

B is correct. This is confirmed, symptomatic, monomeric hyperprolactinaemia above 2500 mIU/L that persists 12 weeks after complete withdrawal of risperidone and substitution with a low-prolactin-liability antipsychotic. Common confounders have also been excluded. UK NHS guidance recommends endocrinology assessment and investigation for prolactinoma, including pituitary MRI, in this situation. Continuing without investigation risks missing pituitary disease. Clozapine can be prolactin-sparing but is not indicated solely for this purpose and would not explain the persistent elevation. Repeated concordant samples and exclusion of macroprolactin make laboratory error unlikely. Cabergoline should not precede diagnostic assessment and is used cautiously with specialist input because dopamine agonists may exacerbate psychosis.

Reference: Essex Partnership University NHS Foundation Trust, Section 22: The Treatment of Hyperprolactinaemia, sections 22.3 and management algorithm, 2021. https://eput.nhs.uk/wp-content/uploads/2025/04/section-22-treatment-of-hyperprolactinaemia-sep-2021.pdf