Ethnic differences in androgens, IGF-I and body fat in healthy prepubertalgirls

Objective: To examine ethnic differences in adrenal androgen production, IG F-I, and : IGFBP-1 and -3 in relation to bone age, insulin, and body compos ition in healthy prepubertal girls. Methods: Serum levels of DHEA-S, androstenedione, IGF-I, and IGFBP-1 and -3 were examined in relation to bone age, insulin, and body composition (dete rmined by dual-energy X-ray absorptiometry) in 47 (19 Caucasian, 9 African- American, 19 Mexican-American) healthy prepubertal girls aged 7.5-9.0 years . Results: Age, weight, height, bone age, androstenedione, insulin, glucose:i nsulin ratios, and IGFBP-3 levels were not statistically different among gr oups. Mexican-American girls had higher % body fat than African-Americans o r Caucasians (P < 0.001). DHEA-S levels in African-Americans were twofold h igher than in Caucasians (P = 0.024), although their % body fat was not sig nificantly different (16.1% and 19.4 %, respectively; P = 0.138). DHEA-S le vels in Mexican-American girls were intermediate. Bone age and weight were significant covariates for DHEA-S levels, Plasma IGP-I levels were also hig her in African-American than in Caucasian or Mexican-American girls (P = 0. 009) Covariance analysis showed that IGF-I levels were influenced mainly by ethnicity (P = 0.009) and were independent of bone age. Despite similar in sulin levels among groups, IGFBP-1 levels were higher in Caucasians than in Mexican-Americans or African-Americans (P < 0.001). Conclusions: In healthy prepubertal girls, DHEA-S concentrations are higher in African-Americans than in Caucasians or Mexican-Americans, even before any clinical evidence of adrenarche. Furthermore, IGF-I concentrations are higher in African-American girls than in Caucasian or Mexican-American girl s which may contribute to the higher DHEA-S levels observed. Conversely, hi gher DHEA-S and IGF-I levels in African-American girls may be indicative of an influence not only of gonadal but also of adrenal androgens on the GH/I GF-I axis.