C O M P R E H E N SIO N Q U E ST IO N S
For Questions 46.1 to 46.3 refer to the following case scenario:
Following brain surgery involving transsphenoidal removal of a pituitary ade-
noma, a patient experienced polyuria, polydipsia, and nocturia. These symp-
toms appeared shortly after the surgery and had never been observed
previously. Osmolarity of the urine was below normal, even if liquid consump-
tion was restricted. Administration of desmopressin alleviated these symptoms.
[46.1] Which of the following possibilities is the most likely hypothesis to
explain these symptoms?
A. Damage to the thirst mechanism from surgical trauma, leading to
excessive consumption of liquids
B. Damage to the pituitary or hypothalamus from surgical trauma,
leading to decreased secretion of vasopressin
C. Onset of diabetes mellitus following surgery
D. Renal injury
E. Oversecretion of angiotensin II following surgery
[46.2] Desmopressin acts mainly by which of the following mechanisms?
A. Stimulating aldosterone secretion by the adrenal gland
B. Increasing synthesis of Na+ transporters in kidney distal tubule
C. Increasing aquaporin insertion into renal distal tubule apical
D. Acting as an insulin sensitizer
E. Stimulation of angiotensin II release
[46.3] Which of the following would be least likely to stimulate vasopressin
release from the posterior pituitary?
C. Angiotensin II
D. Atrial stretch receptors