Insulin-like growth factor-I response to a single bolus of growth hormone is increased in obesity.
Affiliation
Department of Endocrinology, Christie Hospital, Manchester M20 4BX, UK. helena.gleeson@christie-tr.nwest.nhs.ukIssue Date
2005-02
Metadata
Show full item recordAbstract
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/m(2) (n = 19) and women (NW), BMI 24 (19-29) kg/m(2) (n = 23) and with a BMI > 30 (obese men (OM), 41 (30-72) kg/m(2) (n = 15) and women (OW), 43 (30-68) kg/m(2) (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) (R(2) = 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.Citation
Insulin-like growth factor-I response to a single bolus of growth hormone is increased in obesity. 2005, 90 (2):1061-7 J. Clin. Endocrinol. Metab.Journal
The Journal of Clinical Endocrinology and MetabolismDOI
10.1210/jc.2004-0501PubMed ID
15522943Type
ArticleLanguage
enISSN
0021-972Xae974a485f413a2113503eed53cd6c53
10.1210/jc.2004-0501