Isolated ACTH deficiency and primary hypothyroidism: volume-dependent elevation of antidiuretic hormone secretion in the presence of hyponatremia.

The unusual combination of isolated deficiency of ACTH secretion and primary hypothyroidism was demonstrated in a 72-year-old man. Antidiuretic hormone (ADH) levels were elevated despite severe hyponatremia. This abnormality was corrected by salt replacement and hydrocortisone therapy. These results suggest that the elevated ADH levels were appropriate for the volume depletion caused by the hypoadrenalism and were not related to the hypothyroidism.