Co-existent primary hypothyroidism and isolated ACTH deficiency

A 52 year old man is described in whom the simultaneous occurrence of isolated adrenocorticotrophin (ACTH) deficiency and primary hypothyroidism was documented by the determination of six anterior pituitary hormones by specific radioimmunoassays after suitable stimulations. The urinary 17-hydroxycorticosteroids excretion was persistently reduced and was increased by repeated ACTH injections. The low basal metabolic rate, reduced serum thyroid hormones and elevated serum thyrotrophic hormone were consistent with primary hypothyroidism. After resumption of euthyroidism, secretory reserves of growth hormone and ACTH were assessed. The growth hormone reponse to insulin-induced hypoglycaemic was normal. No rise in plasma cortisol and ACTH was observed following insulin-induced hypoglycaemia. Plasma ACTH was not augmented by iv infusion of metyrapone. The pathogenesis of two co-existent endocrine deficiencies was discussed.