OR22-04 Testosterone Doesn’t Impact Body Composition Following Bariatric Surgery in Male Adolescents

Abstract Disclosure: S. Dhindsa: None. T. Jenkins: None. H. Ghanim: None. J.R. Ryder: None. T.H. Inge: None. P. Dandona: None. Background: We have previously published that prior to bariatric surgery in adolescents, 73% of males had subnormal free testosterone (T) concentrations (<6.5 ng/dL). Free T increased by 65% at 12 months, and 80% of the males had normal free T at 24 months. Skeletal muscle mass is partly dependent upon T and insulin like growth factor-1 (IGF-1). Therefore, in this work, we analyzed the relationship between changes in fat free mass (FFM), fat mass (FM), free T and IGF-1 concentrations following bariatric surgery in obese male adolescents. Methods: Teen-Longitudinal Assessment of Bariatric Surgery (Teen-LABS) is a prospective, multicenter, observational study that enrolled adolescents (≤19 years of age) who were undergoing a bariatric surgical procedure from 2007-2012. Body composition was measured by bio-electrical impedance before surgery, and at 6, 12, 24, 36, 48 and 60 months post-surgery. Serum samples were available in 34 males. Total T was measured by liquid chromatography tandem mass spectrometry, sex hormone binding globulin and IGF-1 were measured by ELISA, and free T was calculated. Averages are presented as mean ± SD. Results: The mean age and BMI before bariatric surgery were 17.1±1.7 years and 55.3±10.4 kg/m2 respectively. Mean free T increased from baseline concentration of 4.8±1.8 ng/dl to 7.7±3.2 at month 6, 8.0±2.8 at month 12, 8.4±3.7 at month 36 and 7.8±3.0 at month 60 (p<0.001 for all). Mean IGF-1 increased transiently at 6 months (68±26 to 81±20 ng/mL, p=0.02), but was not different than baseline at month 36 (72±30 ng/mL, p=0.85) and month 60 (65±21 ng/ml, p=0.64). The baseline FM and FFM were 91±35 and 74±15 kg respectively. Serum free T was positively related to FFM (r= 0.37, p=0.05) and negatively to FM (r= -0.44, p=0.02) in males prior to bariatric surgery. IGF-1 was not related to FFM (r= -0.13, p=0.60) but was related to FM (r= 0.52, p=0.02) at baseline. There was a rapid loss of FM after bariatric surgery, with nadir at 12 months and slow regain thereafter for the remainer of follow up. FM changed by -49, -60 and -46 kg at 6, 12 and 60 months (p<0.001). In contrast, there was no change in FFM in males (p=0.76). Baseline FFM was a negative predictor of change in FFM (β= -1.87, 95% CI -2.31, -1.43). Change in free T after bariatric surgery was not related to change in FFM (β= -0.01, 95% CI -0.04, 0.02) or change in FM at any follow up visit (p>0.36). The change in FM or FFM following bariatric surgery among males with normal or subnormal baseline free T was also similar. Serum IGF-1 was not related to change in FM or FFM at any follow up visit. Conclusion: Serum free T and IGF-1 increased in males after bariatric surgery, but the changes were not related to changes in FM or FFM. Presentation: Sunday, July 13, 2025