Effect of weight loss on free insulin-like growth factor-I in obese women with hyposomatotropism.
OBJECTIVE
It has been hypothesized that increased free insulin-like growth factor (IGF)-I levels generated from an increase in IGF-binding protein (IGFBP) protease activity could be the inhibitory mechanism for the decreased growth hormone (GH) secretion observed in obese subjects.


METHODS
In this study, we determined basal and 24-hour levels of free IGF-I and -II, total IGF-I and -II, IGFBP-1, as well as basal IGFBP-2, -3, and -4, acid-labile subunit (ALS), IGFBP-1, -2, and -3 protease activity, and 24-hour GH release in obese women before and after a diet-induced weight loss. Sixteen obese women (age, 29.5+/-1.4 years) participated in a weight loss program and 16 age-matched non-obese women served as controls.


RESULTS
Circulating free IGF-I and 24-hour GH release were significantly decreased in obese women at before weight loss compared with non-obese women (1.29+/-0.12 vs. 0.60+/-0.09 microg/L; p<0.001 and 862+/-90 vs. 404+/-77 mU/24 hours; p<0.001, respectively). Free IGF-I and 24-hour GH release were not inversely correlated to each other. IGFBP-1 and -2 levels were decreased, whereas ALS, IGFBP-3 and -4, and IGFBP-1, -2, and -3 protease activity were similar in obese and non-obese women. Eight of the 16 obese women achieved an average weight loss of 30+/-5 kg during 26 to 60 weeks of dieting. After the considerable weight loss, significant differences in free IGF-I, GH release, and IGFBP-1 and -2 levels were no longer present between previously obese and non-obese women.


CONCLUSIONS
We showed that circulating free IGF-I is markedly decreased in severely obese women and does not per se mediate the concomitant hyposomatotropism. The decreased levels of free IGF-I seem to be transient and restored to normal levels after weight loss.
Rasmussen
Michael H
MH
Department of Endocrinology, Hvidovre Hospital, University of Copenhagen, Denmark. mhr@dadlnet.dk
Juul
Anders
A
Hilsted
Jannik
J
D000273:Adipose Tissue / Q000378:metabolism; D000328:Adult; D001835:Body Weight; D002352:Carrier Proteins / Q000378:metabolism*; D016022:Case-Control Studies; D005260:Female; D013006:Growth Hormone / Q000378:metabolism; D006801:Humans; D007018:Hypopituitarism / Q000097:blood* / Q000150:complications / Q000628:therapy; D007328:Insulin / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D050417:Insulin-Secreting Cells / Q000378:metabolism; D009765:Obesity / Q000097:blood* / Q000150:complications / Q000628:therapy*; D015431:Weight Loss
D002352:Carrier Proteins; D007328:Insulin; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D013006:Growth Hormone; C051815:somatotropin-binding protein