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Dual defects in pulsatile growth hormone secretion and clearance subserve the hyposomatotropism of obesity in man


We have examined the mechanisms underlying reduced circulating GH concentrations in the obese human. Computer-assisted (deconvolution) analysis was used to determine endogenous GH secretory and clearance rates quantitatively from entire 24-h plasma GH concentration profiles. These analyses revealed that the half-life (t 1/2) of endogenous GH was significantly shorter in obese (11.7 +/- 1.6 min) than in normal weight subjects (15.5 +/- 0.81 min; P less than 0.01). The accelerated blood disposal rate of GH was not due to decreased circulating concentrations of GH-binding protein, since the latter were similar in obese (25 +/- 1.0%) and normal weight (24 +/- 2.3%) men. However, obese men had significantly fewer GH secretory bursts (3.2 +/- 0.53 vs. 9.7 +/- 0.67/day; P less than 0.01). Among the rare GH secretory bursts that occurred in obese subjects, there were significantly prolonged mean intersecretory burst intervals (282 +/- 65 vs. 131 +/- 11 min; P less than 0.05). The resultant daily GH production rate in obese men was reduced to one fourth that in normal weight individuals. Both GH secretion rate and burst frequency were negatively correlated with the degree of obesity (ponderal index). The decreases in GH burst frequency and half-life were specific, since GH secretory pulse amplitude (maximal rate of GH release), the mass of GH released per burst, and the duration of computer-resolved GH secretory bursts were not different in obese and normal weight men. We conclude that obese men harbor a double defect in GH dynamics involving both GH secretion and clearance, and that the severity of the GH secretory deficiency is proportionate to the degree of obesity.

Type Journal
ISBN 0021-972X (Print)
Authors Veldhuis, J. D.;Iranmanesh, A.;Ho, K. K.;Waters, M. J.;Johnson, M. L.;Lizarralde, G. :
Published Date 1991-01-01
Published Volume 72
Published Issue 1
Published Pages 51-9
Status Published in-print
URL link to publisher's version