Growth hormone deficiency in patients with idiopathic adrenocorticotropin deficiency resolves during glucocorticoid replacement.

Glucocorticoids (GC) have stimulatory effects on GH secretion in vitro and suppressive effects when administered in pharmacological amounts in vivo. We studied six patients with ACTH deficiency and severely impaired serum GH responses to insulin tolerance tests and arginine infusion tests. All patients underwent the same tests during GC replacement while receiving cortisone acetate in doses ranging from 12.5-25 mg/day. The three patients with idiopathic ACTH deficiency and no evidence of pituitary mass lesions had impaired GH secretion, which returned to normal during GC replacement. In contrast, the three patients with ACTH deficiency and hypothalamo-pituitary mass lesions detected by a computed tomography scan had impaired GH secretion during GC replacement therapy. Our data indicate that in patients with idiopathic ACTH deficiency, an impaired GH response to stimuli reversible during GC replacement therapy may be the functional consequence of the low levels of circulating cortisol. We conclude that physiological serum cortisol levels are necessary for normal serum GH responses to provocative stimuli in man.