Pituitary

Question 1

10% of prolactinomas secrete both prolactin and another hormone, what hormone is that?

Answer 1

Growth hormone

Question 2

What are the main indications for surgical treatment of hyperprolactinemia? (Has to be symptoms or macroadenoma to qualify in the first place)

Answer 2

• failed or can not tolerate medical therapy or long term drug therapy is not acceptable if intrasellar tumor
• growth hormone cosecretion
• neurological symptoms not improving
• surgical decompression if it’s pressing on the optic chiasm
• if macoadenoma and prolactin levels higher than expected due to stalk effect
• symptomatic despite prolactin reduction with medical therapy (failing therapy)

Question 3

What is the Hook effect?

Answer 3

In patients with macroprolactinoma, prolactin levels can be underestimated due to Hook effect.

Normally with the assay the prolactin gets bound between a capture antibody and a detection antibody.

In the Hook effect all the extra prolactin (very high amounts) occupies the detection antibody and prevents binding to the prolactin that is bound to the capture antibody preventing detection and thus causing falsely lowered results.

You can also have blocking antibodies that prevent detection in the assay - I don’t think/know if that is part of hook effect or separate thing

To correct this you must measure prolactin in diluted serum to ensure they are not falsely lowered.