Acute effects of hydrocortisone on circulating growth hormone levels in patients with acromegaly.

Aim of our study was to investigate the acute effects of intravenous infusion of hydrocortisone on circulating growth hormone (GH) levels in acromegaly. We studied 5 adult patients with active acromegaly, 3 males and 2 females; age 52 +/- 3.6 years, body mass index 27 +/- 1 kg/m2. The patients underwent in randomized order from 0 to 120 min: (1) intravenous infusion of saline, 250 ml; (2) bolus intravenous injection of hydrocortisone succinate, 100 mg at time 0 followed by intravenous infusion of hydrocortisone succinate, 250 mg in 250 ml of saline for 120 min. Blood samples for GH, cortisol and glucose assay were taken at -15, 0 (time of beginning of saline or hydrocortisone infusion), 15, 30, 45, 60, 90, 120, 150 and 180 min. In all the acromegalic patients, during hydrocortisone succinate infusion, GH values clearly fell with respect to saline (nadir range 18.4-50.5% with respect to baseline levels) with nadir between 60 and 180 min after the beginning of the infusion. Our data show that acute and sustained hypercortisolism, decreases circulating GH levels in acromegaly. It seems likely that also in acromegalic patients as well as in normal subjects short-term increases in serum cortisol levels may be able to cause an enhancement of hypothalamic somatostatin secretion, which in turn may be responsible for the glucocorticoid-mediated GH inhibition.