Question

Which level of prolactin definitely suggests a prolactinoma?

• A. 300 ng/ml
• B. 150 ng/ml
• C. 200 ng/ml
• D. 100 ng/ml

Hint:

Only a prolactin clearly above 200 ng/ml is diagnostic of a prolactinoma.

Answer 1

The Correct Option is A

Step 1: Prolactinoma is the commonest hyperfunctioning pituitary adenoma and causes hyperprolactinemia with amenorrhea, galactorrhea, loss of libido, and infertility. Step 2: Serum prolactin roughly correlates with tumor size, but mild elevations matter. Levels below 200 ng/ml in a patient with a pituitary mass do NOT necessarily indicate a prolactin-secreting tumor, because stalk compression and many drugs can raise prolactin to that range. Step 3: Therefore only a value clearly above 200 ng/ml is taken as definite evidence of a true prolactinoma. Among the choices, 300 ng/ml is the only level that exceeds the 200 ng/ml threshold, so it definitely suggests a prolactinoma. Step 4: 200, 150, and 100 ng/ml all fall at or below the cut-off and can be explained by non-tumoral causes, so they are not definitive. The medically correct answer is 300 ng/ml.