EFFECT OF GLUCOCORTICOIDS ON THE PARADOXICAL GROWTH-HORMONE RESPONSE TO THYROTROPIN-RELEASING-HORMONE IN PATIENTS WITH ACROMEGALY

It has been hypothesized that in acromegalic patients, as well as in n ormal subjects, acute increases in serum cortisol levels may cause an enhancement of hypothalamic somatostatin secretion, which in turn may be responsible for the glucocorticoid-mediated growth hormone (GH) inh ibition. The aim of this study was to investigate short-term effects o f an intravenous (IV) infusion of hydrocortisone on the GH response to thyrotropin-releasing hormone (TRH) in acromegaly. We studied six adu lt patients with active acromegaly. The group was composed of four wom en and two men with a mean age of 55.8 +/- 6.4 years (range, 27 to 68) and a mean body mass index of 26.7 +/- 1 kg/m(2) (range, 23.3 to 30). All patients underwent the following treatments: (1) hydrocortisone a lone: a bolus IV injection of hydrocortisone succinate 100 mg in 2 mt saline at time -60 minutes, followed by a 120-minute IV infusion of hy drocortisone succinate 250 mg in 250 mt saline from -60 to 60 minutes; (2) TRH + hydrocortisone: a bolus IV injection of TRH 200 mu g 60 min utes after initiation of a 2-hour hydrocortisone infusion; (3) TRH alo ne: a bolus IV injection of TRH at time 0, 60 minutes after initiation of a 2-hour saline infusion. In all six patients, TRH induced large G H increases (absolute peak GH level, 58.1 +/- 23.2 mu g/L; maximum % G H change with respect to baseline, 1,397.8% +/- 807.8%; range, 205% to 5,219%). In the whole group of acromegalic patients, hydrocortisone i nfusion did not significantly affect the mean GH response to TRH (abso lute peak GH level, 45.4 +/- 19.5 mu g/L; maximum % GH change with res pect to 0-minute level, 894.8% +/- 320%; range, 106% to 1,988%). After hydrocortisone + TRH administration, all six patients showed signific antly higher absolute GH values as compared with values obtained with hydrocortisone alone from time 15 to 45 minutes. Our data show that th e paradoxical GH response to TRH in acromegaly is resistant to the inh ibitory action of an acute and sustained elevation of serum cortisol l evel. Copyright (C) 1995 by W.B. Saunders Company