Thyroid function and urine-concentrating ability during lithium treatment

It has been suggested that adenylate cyclase inhibition may be important in the development of both nephrogenic diabetes insipidus and hypothyroidism during lithium treatment. We measured serum thyroxine and urine-concentrating ability (Umax) in response to desmopressin (DDAVP) in 85 patients receiving lithium. Hypothyroidism developed in eight patients while they were taking lithium. Impaired Umax was found in both euthyroid and hypothyroid patients while some hypothyroid patients concentrated their urine well. It is concluded that the dominant mechanisms by which lithium exerts these two effects are different.