OSMOREGULATION OF PLASMA VASOPRESSIN IN 3 CASES WITH ADRENAL INSUFFICIENCY OF DIVERSE ETIOLOGIES

Neurohypophyseal function was studied by hypertonic saline infusion wi th plasma vasopressin measurement in 3 patients with adrenal insuffici ency before and after cortisol replacement. Although each patient had different causes of adrenal insufficiency, all showed impaired water e xcretion before replacement. The first patient with isolated adrenocor ticotropin deficiency had marked hyponatremia and inappropriate vasopr essin secretion which was normalized after replacement, indicating vas opressin hypersecretion during hypoadrenocorticism. The second patient had combined anterior and posterior pituitary deficiency due to postp artum hypopituitarism and showed completely absent vasopressin secreti on, with her polyuria being masked before cortisol replacement, sugges ting a vasopressin-independent intrarenal mechanism of antidiuresis. T he third patient with panhypopituitarism due to a pituitary tumor also had preexisting diabetes insipidus with defective vasopressin secreti on. In this case, however, plasma vasopressin was found to be elevated when adrenal insufficiency and hyponatremia subsequently developed. T ogether, these results indicate that vasopressin hypersecretion does o ccur during adrenal insufficiency, but that the accompanying urinary d iluting defect may be attributable either to vasopressin-dependent or to vasopressin-independent mechanisms.