For adolescent males with severe obesity, bariatric surgery is associated with an increase in testosterone concentrations, according to a study published in the European Journal of Endocrinology. Sandeep Dhindsa, MD, and colleagues examined changes in sex hormones in adolescent males (aged 14.6-19.8) with obesity who underwent bariatric surgery and were followed for 5 years. Study participants lost one-third of their body weight after bariatric surgery; for most participants, maximum weight loss was achieved at 24 months. Free testosterone increased from 0.17 nmol/L at baseline to 0.34 and 0.27 nmol/L at 2 and 5 years, respectively. Total testosterone also increased, from 6.7 nmol/L at baseline to 17.6 and 13.8 nmol/L at 2 and 5 years, respectively. Among participants, 73% had subnormal free testosterone prior to surgery; only 20% and 33% had subnormal free testosterone at 2 and 5 years, respectively. The researchers noted an association between weight regain and a decrease in free testosterone concentration.