Dexamethasone does not increase IGF-I and IGFBP-3 levels in man in the absence of endogenous GH.

It has been previously shown that short-term glucocorticoid administration increases circulating IGF-I and IGFBP-3 levels both in men and rats. An increase in endogenous GH secretion or a direct hepatic effect have been suggested as possible mechanisms. The aim of this study was to investigate the effect of short-term dexamethasone administration (3 mg orally during 7 days) in 8 patients with Sheehan's syndrome in replacement therapy. All patients had GH values <2.5 pg/l after clonidine administration. Before treatment IGF-I values were 9.3 3.6 microg/l (mean +/- SE) and IGFBP-3 levels were 1,195 +/- 208 microg/l. After dexamethasone administration there were no significant changes either in IGF-I or IGFBP-3 values (10.7 +/- 4.1 and 1,110 +/- 214 microg/l, respectively). A significant increase in insulin values was observed after dexamethasone administration (before: 120 +/- 10 micromol/l; after: 175 +/- 27 pmol/l; p<0.05), while glucose levels did not reach statistical significance (before: 4.6 +/- 0.3 mmol/l; after: 5.9 +/- 1.0 mmol/l). Our data suggest that dexamethasone is unable to increase circulating IGF-I and IGFBP-3 levels in man in the absence of endogenous GH.