In panhypopituitarism, which pituitary hormone deficiency is most directly responsible for secondary adrenal insufficiency?

• A. TSH deficiency.
• B. GH deficiency.
• C. ACTH deficiency leading to reduced cortisol production.
• D. Prolactin deficiency.

Answer: (C)

ACTH from the pituitary is the signal that drives cortisol production by the adrenal cortex. In panhypopituitarism, loss of ACTH removes this stimulation, so cortisol production falls—giving secondary adrenal insufficiency. The adrenal cortex still has aldosterone regulation mainly through the renin–angiotensin system, so mineralocorticoid function is typically preserved, which is why the problem centers on cortisol, not aldosterone. Other pituitary deficits do not directly cause the cortisol shortfall: TSH deficiency leads to secondary hypothyroidism, GH deficiency affects growth and metabolism, and prolactin deficiency has minimal direct impact on adrenal cortisol. So the deficiency most directly responsible is the lack of ACTH leading to reduced cortisol production.