Interleukin-2 Transiently Inhibits Pulsatile Growth Hormone Secretion in Young but not Older Healthy Men.

Abstract

CONTEXT\nInterleukin-2 (IL2), a proinflammatory cytokine, has been used to treat malignancies. Increased cortisol and ACTH were noted, but GH secretion was not investigated in detail.\n\n\nOBJECTIVE\nWe quantified GH secretion after a single sc injection of IL2 in 17 young and 18 older healthy men in relation to dose, age and body composition.\n\n\nDESIGN\nThis was a placebo-controlled, blinded, prospectively randomized cross-over study. At 20:00\xa0h IL2 (3 or 6 million units per m2 ) or saline was injected sc. Lights were off between 23:00 and 07:00\xa0h. Blood was sampled at 10-min intervals for 24\xa0h.\n\n\nOUTCOME MEASURES\nDeconvolution analysis of GH secretion.\n\n\nRESULTS\nGH profiles were pulsatile under both experimental conditions and lower in older than young volunteers. Since the effect of IL2 might be time-limited, GH analyses were performed on the complete 24-h series and the 6\xa0h after IL2 administration. Total and pulsatile 24-h GH secretion decreased nonsignificantly.Pulsatile secretion fell over the first 6\xa0h after IL2 (P=0.034), with visceral fat as covariate (P=0.003), but not age(P=0.10). Plots of cumulative 2-h bins of GH pulse mass showed a distinction by treatment and age groups: a temporary GH decrease of 32% and 28% occurred in the first 2-h bins after midnight (P=0.019 and 0.038) in young subjects, while in older subjects no differences were present at any time point.\n\n\nCONCLUSION\nThis study demonstrates that IL2 temporarily diminishes GH secretion in young, but not elderly, men.