Free versus Total Testosterone as a marker of Leydig Cell Function throughout Pubertal Development in Obese Male Adolescents

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SAT 677-696-Obesity Physiology & Epidemiology
Clinical
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-692
Sara Vandewalle*1, Youri Taes1, Tom Fiers1, Inge Roggen2, Maria Van Helvoirt3, Patrick Debode3, Jean De Schepper2 and Jean-Marc Kaufman1
1Ghent University Hospital, Ghent, Belgium, 2Brussels University Hospital, Brussels, Belgium, 3Zeepreventorium, De Haan, Belgium
Context: Only very few and contrasting data concerning male sex steroids in obese male adolescents have been published. The use of direct immunoassays for testosterone determination and the poor assessment of pubertal development might explain these discordant findings between studies.

Objective: This study aimed therefore to analyse serum testosterone and free testosterone concentration by using gold-standard techniques, i.e.  liquid chromatography tandem mass and spectroscopy (LC-MS/MS) and equilibrium dialysis, in association with a detailed clinical assessment  (Tanner stage and testisvolume) in obese male adolescents.

Methods: 51 male obese adolescents (mean BMI sds: + 2.55), aged 10-19y at start of a residential obesity treatment program and 51 age-matched healthy (mean BMI sds: -0.17) controls were studied. Pubertal status was assessed according to the method of Marshall and Tanner and testicular volume was measured using the Prader orchidometer by the same investigator. Testosterone (by LC-MS/MS),  free testosterone (by equilibrium dialysis), LH and SHBG (by commercial immunoassays ) were measured.  

Results: Compared to age-matched controls, there was no significant difference in genital staging (obese vs controls: G1: 12 vs 10 %; P2: 18 vs  16 %; P3:12 vs 16 %; P4: 33  vs 33 %; P5: 26 vs 26 %; NS) and mean (±SD) testicular volume (15 ± 8 ml vs 15 ± 8 ml; NS). While both testosterone (247 (35-355) vs. 407 (81.1-482) ng/l; p=0.05) and SHBG (2.5 (1.9-4.3) vs. 5.5 (4.0-8.9) nmol/l; p<0.001) concentrations were significantly lower in the obese group, free testosterone (5.6 (0.6-9.0) vs. 5.7 (0.7-9.1) ng/l; NS) and LH concentrations (3.6 (1.6-4.7) vs. 2.5 (1.6-4.4) mU/ml; NS)) were comparable between both groups. As expected, higher total and free testosterone levels were found with advancing pubertal development in both groups. Although obese adolescents had lower SHBG and testosterone levels at each pubertal stage, free testosterone levels were similar from Tanner stage  G1 to G4.

Conclusion: Testosterone and SHBG concentrations but not the free testosterone concentration were lower in  obese adolescents compared to age-matched controls, while  they presented a normal and comparable testicular volume and pubertal development. Therefore, in adolescent obesity free testosterone concentration reflects better the  Leydig cell function than total testosterone.

Nothing to Disclose: SV, YT, TF, IR, MV, PD, JD, JMK

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: This work was supported in part by Grant G.0867.11 from the Research Foundation Flanders (FWO Vlaanderen). Sara Vandewalle is a holder of a PhD fellowship and Youri Taes is holder of a postdoctoral fellowship from the Research Foundation Flanders.