A 22-year-old subfertile woman has amenorrhoea, recent frequent headaches and bilateral nipple discharge. Investigations show an elevated serum prolactin. What is the most appropriate investigation?

Answer: D. MRI of the head (pituitary)

Hyperprolactinaemia with headaches

Amenorrhoea, galactorrhoea and an elevated prolactin, together with recent headaches, strongly suggest a pituitary tumour (prolactinoma).

Why MRI of the head

• MRI of the pituitary is the investigation of choice to image a pituitary adenoma - it best visualises soft tissue and the pituitary/hypothalamic region.
• The headaches raise concern about a macroadenoma with possible mass effect, making imaging important.

Management context

Prolactinomas/hyperprolactinaemia are treated with a dopamine agonist (cabergoline or bromocriptine), which lowers prolactin, restores ovulation and shrinks the tumour.

Why D

MRI of the head best images a suspected pituitary tumour.

Why the others are wrong

CT is less sensitive than MRI for the pituitary; nipple-discharge cytology and a pituitary X-ray are not useful here; thyroid function (though hypothyroidism can raise prolactin) does not explain the headaches and would not image a tumour - MRI is the appropriate investigation.