The effect of lithium therapy on arginine vasopressin secretion and thirst in man.

Lithium therapy is known to reduce the renal responsiveness to arginine vasopressin (AVP: the antidiuretic hormone in man) and a proportion of treated patients develop polyuria and polydipsia. In this study seven nonpolyuric female patients receiving lithium treatment for an affective disorder (lithium group) were age-matched with seven healthy females (control group). The mean response of plasma AVP to osmotic stimulation was significantly enhanced in the lithium group but the mean osmotic threshold for AVP release was unchanged. Thirst appreciation in the lithium group commenced and increased overall at an osmotic stimulus 5 mmol/kg less than the control group. It is suggested that primary thirst does play a role in the expression of lithium-induced polyuria.