Endocrine Abstracts

Background: Data concerning pubertal development and testosterone (T) in obese male adolescents (ObA) are scarce and contrasting. Underperforming T immunoassays and poor assessment of pubertal development might explain discordant findings. Although SHBG is markedly affected, few studies report free T (FT) levels.

Objective: To study if ObA have conserved FT levels despite low total T (TT) and to investigate if FT is a better indicator of androgen exposure than TT by studying pubertal development, testicular volume, and PSA.

Methods: Ninety ObA (mean BMI s.d.+2.6), aged 10–19 year at start of a residential obesity treatment program and 90 age-matched (mean BMI s.d.−0.04) controls were studied. Pubertal status was assessed according to the Marshall and Tanner method and testicular volume was measured using a Prader orchidometer. Morning concentration of TT (by LC–MS/MS), FT (by equilibrium dialysis), LH, SHBG, and PSA (by commercial immunoassays) were measured.

Results: Compared to age-matched controls, there was no significant difference in tanner genital staging (obese vs controls:G1:8.8 vs 12.1; G2:18.7 vs 15.4; G3:14.3 vs 13.2; G4:33.0 vs 34.1, G5:25.3 vs 25.3%; NS) and mean testicular volume at the different pubertal stages. While both SHBG (23.3 (17.2–37.1) vs 42.8 (32.9–82.8) nmol/l; P<0.001) and TT (241 (41–339) vs 333 (57.1–502) ng/dl; P<0.01) concentrations were significantly lower in obese boys, FT (5.6 (0.8–8.5) vs 6.3 (0.5–10.6) ng/dl; NS), LH (3.4 (1.7–4.8) vs 2.8 (1.6–4.2) U/l; NS), and PSA (0.19 (0.01–0.38) vs (0.19 (0.01–0.38) μg/l; NS) were comparable. SHBG and TT were lower at all pubertal stages, whereas FT and PSA were preserved except for FT at stage 5.

Conclusion: SHBG and TT but not FT concentrations were lower in ObA compared to lean controls. Since they presented a normal pubertal development, a comparable testicular volume and similar PSA levels, one can state that FT reflects better Leydig cell function than TT in adolescent obesity.