A case of hypopituitarism with diabetes insipidus and loss of thirst. Role of antidiuretic hormone and angiotensin II in the control of urine flow and osmolality.

A 20-yr-old male was found to have diabetes insipidus is association with panhypopituitarism but without any focal neurological lesion being identified. He was initially treated with steroid supplements, the features of diabetes insipidus being controlled with a thiazide diuretic. Eighteen months later the patient lost thirst sensation and stopped treatment, subsequently being re-admitted with severe dehydration, oliguria and focal neurological signs. Further investigation, including brain biopsy, confirmed the presence of an atypical pinealoma which was considered inoperable. Measurements of plasma antidiuretic hormone (ADH) and angiotensin II (AII) concentrations during the severe dehydration showed very high levels of AII, but inappropriately low plasma ADH levels for the severity of dehydration. We consider that the evidence obtained from this case supports the view that the oliguria with hypertonic urine present during severe dehydration was due to a direct renal action of the very high AII levels, possibly supplemented by the residual ADH secretion.