D

Reasoning: Loss of pituitary ACTH after transsphenoidal hypophysectomy produces secondary adrenal insufficiency, in which cortisol must be replaced but aldosterone production is preserved because it is regulated mainly by the renin-angiotensin-K⁺ system rather than ACTH. Therefore fludrocortisone (mineralocorticoid) is not required, whereas thyroxine, sex-steroid, and glucocorticoid replacement typically are needed. [Reingardiene, 2002, PMID 12474663; Reimondo, 2008, PMID 18418713]