A 57-year-old man complained to his physician of that he was always thirsty and had frequent and profuse micturition. The man recently diagnosed with bipolar disorder, had been receiving lithium for three weeks.
Which of the following was most likely the cause of the patient’s symptoms?
A. Blockade of Na+ reabsorption in the thick ascending loop of Henle B. Blockade of the ADH-induced increase of cAMP in the collecting tubule C. Increased glucose plasma levels D. Stimulation of the thirst center in the hypothalamus E. Blockade of vasopressin secretion from the pituitary
Blockade of the adh-induced increase of camp in the collecting tubule-learning objective: describe the adverse effects of lithium.
polyuria and polydipsia are common side effects of lithium due, at least in part, to inhibition of
the vasopressin-induced increase of camp on the kidney (lithium inhibits adenylyl cyclase).
this leads to elevated circulating levels of vasopressin and lack of responsiveness of the
collecting tubule, i.e. nephrogenic diabetes insipidus.
a) lithium has no effect on renal reabsorption of sodium in this part of the nephron.
c) lithium has no effect on glucose plasma levels.
d) stimulation of the thirst center in the hypothalamus is the consequence, not the cause, of
e) since the collecting tubule is less sensitive to vasopressin the secretion of the hormone is
stimulated, not blocked.