On this page
Study tools
Write your answer
Saved on this device. No marking — you are the marker.
Q1: Definition and mechanism (2 min)
Examiner: Define a prolactinoma. Why does it cause amenorrhoea and infertility?
Expected answer:
- A prolactinoma is a benign pituitary lactotroph adenoma that autonomously secretes prolactin; it is the most common hormonally active pituitary tumour.
- Size defines microprolactinoma (under 10 mm) versus macroprolactinoma (10 mm or more).
- Excess prolactin inhibits hypothalamic GnRH, lowering FSH and LH and producing hypogonadotropic hypogonadism: amenorrhoea, anovulation, infertility, low libido and (over time) osteoporosis.
- Prolactin also has a direct lactogenic effect on the breast, causing galactorrhoea.
Q2: Causes of hyperprolactinaemia and investigation (3 min)
Examiner: A young woman has a raised prolactin. What else must you exclude, and how do you investigate?
Expected answer:
- Always exclude pregnancy first (beta-hCG) — the commonest physiological cause.
- Other causes: drugs (antipsychotics — risperidone, haloperidol; metoclopramide, domperidone; SSRIs; opioids; verapamil; methyldopa; oestrogens); primary hypothyroidism (TRH stimulates prolactin); chronic kidney disease and cirrhosis; stress, sleep, nipple stimulation; macroprolactin (bio-inactive complex).
- Stalk effect: a large non-functioning sellar mass compresses the pituitary stalk, interrupting dopamine delivery and raising prolactin only modestly (usually under 2000 mU/L) — a big tumour with a small prolactin rise.
- Confirm with at least two resting fasting prolactin samples; send TSH, U&E, LFTs, macroprolactin; pituitary MRI to localise the tumour; visual fields and full pituitary axes for macroadenomas.
Q3: Treatment (3 min)
Examiner: Walk me through the management.
Expected answer:
- First-line is medical with a dopamine agonist — cabergoline preferred (more efficacious and better tolerated than bromocriptine), even for macroprolactinomas with visual loss.
- Cabergoline normalises prolactin, shrinks the tumour, restores fertility and often relieves visual field defects within weeks.
- Bromocriptine is the alternative with the most pregnancy safety data.
- Transsphenoidal surgery is reserved for dopamine-agonist resistance or intolerance, pituitary apoplexy, CSF leak, optic chiasm compression unresponsive to drugs, or patient choice.
- Radiotherapy is a last resort for aggressive or resistant disease.
- Withdraw offending drugs, treat hypothyroidism, and replace other deficient pituitary axes.
Q4: Pregnancy, complications and pearls (2 min)
Examiner: She wants a pregnancy and a child. How do you manage her, and what are the complications?
Expected answer:
- Warn that cabergoline restores ovulation quickly — advise contraception if pregnancy is not desired.
- Microprolactinoma in pregnancy: stop the dopamine agonist once pregnant; risk of symptomatic enlargement is low (under 5%); monitor clinically.
- Macroprolactinoma in pregnancy: continue the dopamine agonist and check visual fields each trimester because enlargement risk exceeds 20%.
- Complications: infertility and osteoporosis from hypogonadism; visual loss and hypopituitarism from mass effect; dopamine-agonist adverse effects (nausea, postural hypotension, impulse control disorders, and high-dose cardiac valvulopathy).
- Watch for the high-dose hook effect in very large tumours — dilute the sample.
- Emergency: pituitary apoplexy (sudden headache, visual loss, ophthalmoplegia) — IV hydrocortisone and urgent surgery.