Fat distribution in non-obese girls with and without precocious pubarche: central adiposity related to insulinaemia and androgenaemia from prepuberty to postmenarche

Abstract

Objective: Precocious pubarche (PP) in girls is associated with hyperinsulinaemia and dyslipidaemia of prepubertal onset, and with ovarian hyperandrogenism and ovulatory dysfunction in adolescence, particularly if they also had prenatal growth restraint and postnatal growth acceleration. Hyperinsulinaemia may be the pathogenic key factor, possibly amplified by hyperandrogenaemia. While such PP girls do not have increased body mass index (BMI), we hypothesized that body fat mass and fat distribution may differ between PP girls and matched controls, and may relate to insulin and androgen levels.

Patients and design: Sixty-seven PP girls (age range 6.0-18.0 years) and 65 control girls matched for age and pubertal stage (5.9-18.0 years) had height, weight, waist and hip circumferences measured, and dual-energy X-ray absorptiometry (DXA) assessment of total body fat mass, and fat mass in abdominal and truncal regions. All girls had fasting plasma glucose, serum insulin, lipids, testosterone and SHBG levels measured; PP girls also had a standard 2-h oral glucose tolerance test (oGTT).

Results: Despite no differences in BMI, PP girls had significantly larger waist circumference, waist-to-hip ratio, total fat mass, percentage fat mass, abdominal fat mass, and truncal fat mass vs. controls in each pubertal stage. Overall, fasting insulin levels, free androgen index (FAI) and blood lipid levels were more closely related to central fat than to total body fat mass. In a multiple regression analysis, truncal fat mass was independently related to both fasting insulin (P = 0.009) and FAI (P < 0.0001). Abdominal fat mass was inversely related to birthweight (r = -0.25, P = 0.001). In PP girls, central fat mass was positively related to insulin levels after oGTT (truncal fat vs. 30 min insulin; r = 0.46, P < 0.0005).

Conclusions: Precocious pubarche girls had excess total body and central fat mass throughout all pubertal stages, and increased central fat was related to hyperinsulinaemia and hyperandrogenaemia. It remains to be verified whether body composition in PP girls can be normalized by insulin-sensitization and/or antiandrogen therapy.