The effects of dexamethasone treatment on immunoreactive and bioactive insulin-like growth factors (IGFs) and IGF-binding proteins in normal male volunteers

Abstract

Glucocorticoids inhibit somatic growth in man and laboratory animals, and have long been regarded as suppressors of both stimulated GH secretion and insulin-like growth factor (IGF) activity. Recent evidence suggests, however, that glucocorticoids can be potent GH secretagogues in their own right with concomitant increases in circulating IGF-I levels. IGFs circulate tightly bound to a group of high-affinity binding proteins (IGFBPs) which modulate their actions. In order to investigate the effects of glucocorticoids on serum levels of IGFs and IGFBPs, normal male volunteers were sampled over 24-h periods before and directly after treatment with dexamethasone (2 mg twice daily) for 96 h. Following dexamethasone administration, all volunteers showed a marked increase in mean +/- S.E.M. IGF-I levels over the 24-h sampling period (292.2 +/- 31.8 before dexamethasone, 425.9 +/- 37 micrograms/l after dexamethasone, P < 0.005); there was no change in mean IGF-II levels. Integrated mean insulin levels were raised by dexamethasone treatment (50 +/- 4.6 before dexamethasone, 117 +/- 13.4 mU/l after dexamethasone, P = 0.002) and IGFBP-1 was significantly suppressed (42.9 +/- 8.2 before dexamethasone, 28.0 +/- 7.9 micrograms/l after dexamethasone, P < 0.001). IGFBP-2 levels were similarly suppressed after dexamethasone (319.5 +/- 24.5 before dexamethasone, 214.8 +/- 8.5 micrograms/l after dexamethasone, P = 0.002), and there was a significant increase in IGFBP-3 levels from 3.24 +/- 0.25 to 3.67 +/- 0.32 mg/l (P = 0.0153). Mean IGF bioactivity over the sampling period after dexamethasone was reduced by approximately 60% (0.93 +/- 0.39 before dexamethasone, 0.39 +/- 0.05 U/ml after dexamethasone, P < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Glucocorticoids are not necessary for the inhibitory effect of endotoxic shock on serum IGF-I and hepatic IGF-I mRNA

“…Dexamethasone had little effect on serum IGF-I but decreases IGF-I mRNA abundance in the liver (Luo & Murphy 1989). In normal male volunteers, dexamethasone administration increased circulating IGF-I levels, but reduced the IGF-I bioactivity measured by bioassay (Miell et al 1993). It has also been reported that glucocorticoid administration in rats increases total serum IGF-I, but decreases serum free IGF-I (Skjaerbaek et al 1998).…”

Alcohol Withdrawal–Induced Change in Lipoprotein(a)

“…IGF-I levels may be reduced 43 or unaffected 44 by corticosteroid excess. IGFBP-1 levels have been shown to decrease 45 or increase 46 during cortisol administration. In addition, dexamethasone treatment after renal transplantation has been shown to induce a dose-dependent reduction in Lp(a).…”

Differential regulation of IGF-binding proteins in rabbit costal chondrocytes by IGF-I and dexamethasone

“…Regulation of IGFBP-3 by glucocorticoids was also studied in vivo. Both in rats and in humans, administration of dexamethasone led to an increase in serum IGFBP-3 levels (Luo & Murphy 1990, Miell et al 1993. Obviously, the effects of glucocorticoids are broad and complex, and regulation of IGFBP-3 in vivo may be through an indirect mechanism.…”