This Article Full Text Full Text (PDF) All Versions of this Article: 90/2/1061    most recent Author Manuscript (PDF) Submit a related Letter to the Editor Purchase Article View Shopping Cart Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Gleeson, H. K. Articles by Shalet, S. M. Search for Related Content PubMed PubMed Citation Articles by Gleeson, H. K. Articles by Shalet, S. M. Pubmed/NCBI databases Gene GEO Profiles HomoloGene UniGene Substance via MeSH Medline Plus Health Information Nutrition Obesity Related Collections Neuroendocrinology and Pituitary Obesity

Insulin-Like Growth Factor-I Response to a Single Bolus of Growth Hormone Is Increased in Obesity

Department of Endocrinology, Christie Hospital, Manchester M20 4BX, United Kingdom

Address all correspondence and requests for reprints to: Professor S. M. Shalet, Department of Endocrinology, Christie Hospital, Wilmslow Road, Withington, Manchester M20 4BX, United Kingdom. E-mail: helena.gleeson{at}christie-tr.nwest.nhs.uk.

Reduced GH levels are found in obesity; despite which IGF-I levels are reported as low normal or normal. Previously peripheral responsiveness to GH has been investigated and reported to be increased in obese men and premenopausal women; however, the use of weight-based GH doses in these studies made data interpretation difficult. GH binding protein (GHBP) measurement constitutes an indirect estimate of GH receptor number. GHBP has been reported to be elevated in obesity; however, results from a recent study implied that this was only in men and premenopausal but not postmenopausal women. Therefore, we pursued this question further by challenging a cohort of healthy normal-weight and obese subjects with a non-weight-based dose of GH and examined the relationship of GHBP with the IGF-I response in the context of their body composition.

Ninety-eight (40 male) healthy subjects with a wide range of ages and body mass index (BMI) were studied. Ninety-one (34 male) of these subjects were divided into groups of similar age: men and women with a BMI less than 30 [normal-weight men (NM), BMI 26 (22–29) kg/m² (n = 19) and women (NW), BMI 24 (19–29) kg/m² (n = 23) and with a BMI > 30 (obese men (OM), 41 (30–72) kg/m² (n = 15) and women (OW), 43 (30–68) kg/m² (n = 34)]. Fat mass and percentage fat were measured by a bioelectrical impedance analyzer. An IGF-I generation test, which involved a sc injection of 21 IU (7 mg) GH, was performed. At baseline serum samples were assayed for GHBP; serum IGF-I and IGFBP3 levels were measured both at baseline and 24 h after GH administration.

There was a higher increment IGF-I in obese men and women, compared with the equivalent normal-weight subjects [NM vs. OM: 245 (33–342) vs. 291 (192–427) ng/ml (P < 0.05); NW vs. OW: 220 (103–435) vs. 315 (144–450) ng/ml (P < 0.0005)]. Increment IGF-I was negatively correlated with baseline IGF-I (F = 12.1) and positively correlated with GHBP (F = 18.2) (R² = 0.29). GHBP levels were significantly higher in OM and OW (pre- and postmenopausal) than in the equivalent normal-weight groups [NM vs. OM: 2175 (995–4190) vs. 3030 (1540–5470) pmol/liter (P < 0.05); NW vs. OW: 2131 (1010–5040) vs. 3585 (1540–5740) pmol/liter (P < 0.0005)]. GHBP levels correlated highly with BMI, percentage fat, and fat mass (R > 0.6, P < 0.0001). Baseline IGF-I was not affected by body composition.

In conclusion, in obese compared with normal-weight healthy subjects, there is a larger increment IGF-I to a single bolus of GH in men, and irrespective of menopausal status, women. Increment IGF-I is associated positively with GHBP level, which in turn is associated with markers of increasing obesity in men and women. GH responsiveness is increased in obesity.

This article has been cited by other articles:

				N. Bouhours-Nouet, F. Gatelais, F. Boux de Casson, S. Rouleau, and R. Coutant The Insulin-Like Growth Factor-I Response to Growth Hormone Is Increased in Prepubertal Children with Obesity and Tall Stature J. Clin. Endocrinol. Metab., February 1, 2007; 92(2): 629 - 635. [Abstract] [Full Text] [PDF]

				Y. Wei, Z. Rhani, and C. G. Goodyer Characterization of Growth Hormone Receptor Messenger Ribonucleic Acid Variants in Human Adipocytes J. Clin. Endocrinol. Metab., May 1, 2006; 91(5): 1901 - 1908. [Abstract] [Full Text] [PDF]

				V. Popovic, D. Miljic, S. Pekic, P. Pesko, M. Djurovic, M. Doknic, S. Damjanovic, D. Micic, G. Cvijovic, J. Glodic, et al. Low Plasma Ghrelin Level in Gastrectomized Patients Is Accompanied by Enhanced Sensitivity to the Ghrelin-Induced Growth Hormone Release J. Clin. Endocrinol. Metab., April 1, 2005; 90(4): 2187 - 2191. [Abstract] [Full Text] [PDF]