A patient with a craniopharyngioma has pan-hypopituitarism. Which hormonal axis will clinically manifest EARLIEST and most prominently after complete hypophyseal stalk section?

• A Growth hormone axis
• B Prolactin secretion rises paradoxically ✓
• C Thyroid-stimulating hormone axis
• D ACTH-cortisol axis fails first due to cortisol's short half-life

Explanation

Stalk section eliminates dopaminergic inhibition of lactotrophs, causing prolactin to rise paradoxically — unlike all other anterior pituitary hormones which fall. This distinguishes prolactin from GH, TSH, ACTH, FSH, and LH, all of which require hypothalamic releasing factors and therefore decrease. The paradoxical rise in prolactin is a hallmark of stalk compression or section.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.