Elevated serum IGF-I, but unaltered sex steroid levels, in healthy boys with pubertal gynaecomastia.

Objective: Pubertal gynaecomastia is a very common condition. Although the underlying aetiology is poorly understood, it is generally accepted that excess of oestrogens and deficit of androgens are involved in the pathogenesis. Furthermore, adiposity as well as the GH/IGF-I axis may play a role. In this study, we elucidate the association of adiposity and levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), sex hormone-binding globulin (SHBG), testosterone, oestrogen, IGF-I and IGFBP-3 with the presence of pubertal gynaecomastia in a large cohort of healthy boys.

Patients: A total of 501 healthy Danish school boys (aged 6·1-19·8 year) from the COPENHAGEN Puberty Study.

Measurements: Anthropometry and pubertal stages (PH1-6 and G1-5) were evaluated, and the presence of gynaecomastia was assessed. Body fat percentage was calculated by means of four skin folds and impedance. Nonfasting blood samples were analysed for FSH, LH, testosterone, SHBG, oestradiol, IGF-I, IGFBP-3 and prolactin.

Results: We found that 23% (31/133) of all pubertal boys had gynaecomastia. More specifically, 63% (10/16) of boys in genital stage 4 had gynaecomastia. Boys with gynaecomastia had significantly higher IGF-I levels compared with controls (IGF-I SD-score 0·72 vs -0·037, P < 0·001). This difference was maintained after adjusting for confounders (age and pubertal stage). Sex steroid levels, oestradiol/testosterone ratio or free testosterone were not associated with the presence of gynaecomastia with or without adjustment for confounders.

Conclusions: IGF-I levels were elevated in healthy boys with pubertal gynaecomastia compared with boys without gynaecomastia, whereas sex steroid levels did not differ. We speculate that the GH-IGF-I axis may be involved in the pathogenesis of pubertal gynaecomastia.