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A 28-year-old woman presents to the outpatient endocrine clinic complaining of breast milk discharge for the past 6 weeks. She denies recent pregnancy, visual changes, or headaches. Her menstrual cycles have become irregular over the past few months. She has a history of bipolar disorder, for which she was started on risperidone 5 months ago.
Physical examination shows galactorrhea. Serum prolactin is elevated at 7845 mU/L. A urine pregnancy test is negative.
Which of the following is the most likely cause of her condition?
A. Prolactinoma B. Drug-induced hyperprolactinemia C. Craniopharyngioma D. Non-functioning pituitary adenoma E. Primary hypothyroidism
Correct Answer: B. Drug-induced hyperprolactinemia
✅ Explanation:
Risperidone is a dopamine D2 receptor antagonist.
Dopamine normally inhibits prolactin secretion from the anterior pituitary.
Blocking this inhibition leads to hyperprolactinemia, which can cause:
Galactorrhea
Amenorrhea or oligomenorrhea
Infertility
A prolactin level up to ~10,000 mU/L can be seen with antipsychotic drugs.
There is no need for MRI unless levels are very high (>10,000 mU/L) or there are other symptoms (e.g. visual loss).
Why the other options are incorrect:
❌ A. Prolactinoma
Prolactinomas typically present similarly (galactorrhea, amenorrhea), but:
Macroprolactinomas usually have levels >10,000 mU/L and may cause visual symptoms or headaches.
In this case, there's no visual disturbance, and the patient is on a known prolactin-elevating drug.
Prolactin level is not high enough to confidently diagnose a macroadenoma without imaging.
❌ C. Craniopharyngioma
Rare tumor near the pituitary.
Often presents with visual field defects, delayed puberty, or panhypopituitarism.
Does not typically cause isolated hyperprolactinemia to this degree.
No signs of increased intracranial pressure or visual changes here.
❌ D. Non-functioning pituitary adenoma
May cause mild prolactin elevation due to stalk effect, but not usually >2000 mU/L.
Usually presents with mass effect (e.g. headache, vision problems).
Again, no such features in this case.
❌ E. Primary hypothyroidism
Can lead to mild hyperprolactinemia via elevated TRH stimulating prolactin release.
But levels are usually mildly elevated (<2000 mU/L).
Also expect other symptoms: weight gain, cold intolerance, constipation, bradycardia, etc.
No such signs are present here.
Q A 45-year-old man is admitted to the medical ward with new-onset seizures and muscle cramps. He underwent a total thyroidectomy 5 days ago for thyroid cancer. On examination, he has positive Chvostek’s and Trousseau’s signs. His serum calcium level is 1.85 mmol/L (normal 2.1–2.6 mmol/L).
What is the best immediate management?
A. Oral calcium carbonate supplementation B. Intravenous calcium gluconate C. Intravenous magnesium sulfate D. Oral calcitriol only E. Observation and repeat blood tests
Ans
B. Intravenous calcium gluconate
Explanation:
The symptoms described (paresthesia around mouth, hands, and feet) suggest acute symptomatic hypocalcemia, likely due to post-thyroidectomy hypoparathyroidism or transient hypoparathyroidism.
Although her calcium level (2.02 mmol/L) is only mildly low, the presence of neuromuscular symptoms (tingling) is an indication for immediate intravenous calcium to quickly restore calcium levels and prevent progression to tetany or seizures.
Oral calcium alone would be too slow in this symptomatic patient.
IV magnesium is used only if magnesium deficiency is confirmed.
Calcitriol is often started but is not immediate management; it takes days to weeks to raise calcium.
Observation without treatment is unsafe given symptoms.
