Weight loss after bariatric surgery linked to higher testosterone for male adolescents
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Adolescent boys with severe obesity who lost weight loss with bariatric surgery saw increases in free and total testosterone, according to study findings published in the European Journal of Endocrinology.
“Men usually achieve their peak testosterone concentrations at puberty, followed by a gradual decline — 1% per year — for the rest of their life,” Sandeep Dhindsa, MD, professor of medicine and chief of the division of endocrinology and metabolism at Saint Louis University, told Healio. “Adolescent males with obesity start off with a lower testosterone. We do not know the long-term effects on fertility and sexual function. The good news is that weight loss normalizes testosterone concentrations. In study participants who regained weight after the initial weight loss following bariatric surgery, we saw that their testosterone levels started to drift down.”
Dhindsa and colleagues analyzed data from the Teen-Longitudinal Assessment of Bariatric Surgery (Teen-LABS) study, a prospective multicenter observational study of adolescents aged 19 years and younger who underwent bariatric surgery from March 2007 to February 2012. Boys who had baseline serum samples collected to measure testosterone, estradiol, sex hormone-binding globulin and gonadotropins were included in the analysis. Serum samples were collect at baseline before surgery and at 6, 12, 24, 36, 48 and 60 months after surgery.
Testosterone levels double post-bariatric surgery
There were 34 boys included in the study, of whom 74% were older than 16 years at baseline. The participants had a mean BMI reduction of 28.7% 5 years after surgery.
Total testosterone increased from 6.7 nmol/L at baseline to 17.6 nmol/L at 2 years (P < .001), and free testosterone doubled from 0.17 nmol/L at baseline to 0.34 nmol/L at 2 years (P < .001).
“Previous studies in adults showed a modest increase of 30% to 40% in testosterone after bariatric surgery,” Paresh Dandona, MD, PhD, the study’s senior author and principal investigator, SUNY distinguished professor and chief of endocrinology in the department of medicine at the University of Buffalo and an Endocrine Today Editorial Board Member, told Healio. “Children have a very active hypothalamic-pituitary-adrenal axis because they are in the process of maturation. The axis is much more active, and therefore, they responded with an amazing 100% increase in testosterone concentrations.”
At baseline, 79.4% of the study cohort had below normal total testosterone levels of less than 9.2 nmol/L. At 5 years, that percentage declined to 21.6% (P < .001). Subnormal free testosterone of less than 0.23 nmol/L was observed in 72.7% of participants at baseline and 33.1% at 5 years. At 5 years, 71.4% of those with a low baseline total testosterone increased their concentration to a normal level. During the study, each 10% decrease in BMI was associated with increased odds for normalization of free testosterone (RR = 1.24; 95% CI, 1.02-1.51; P = .034).
Most participants reached their nadir weight at either 1 year or 2 years after surgery. The median percentage body weight regain was 11.4% 1 year following nadir and 26.7% 2 years after nadir. After adjusting for covariates, an increase in the percentage of body weight regain was associated with a decline in the percentage of free testosterone change from baseline (beta = –1.87; 95% CI, –3.3 to –0.43; P = .015).
While total estradiol did not differ during the duration of the study, free estradiol declined from baseline at 3 years (P = .01) before increasing back to near baseline levels at 5 years. BMI and testosterone were positively associated with both total and free estradiol level (P < .001 for all). Follicle-stimulating hormone levels increased at 2 years compared with baseline. Changes in luteinizing hormone and follicle-stimulating hormone during the study correlated with each other, but were not related to changes in body weight, C-reactive protein or insulin resistance.
Linking body weight with testosterone
Dandona said the clinical implications of the study go beyond weight loss following bariatric surgery, saying the findings reveal an association between weight trajectory and testosterone levels among adolescents.
“Those boys who regained wait declined their testosterone again,” Dandona said. “You have a bi-phasic effect, weight loss led to increased testosterone and weight regain led to lost testosterone that they had gained. Those who maintained their weight loss maintained their testosterone. It’s an extremely important set of data to show that obesity itself, even without diabetes, is a very important cause of the male hypogonadal state.”
Dandona and Dhindsa said more studies are needed to investigate factors contributing to the increase in testosterone after bariatric surgery.
“The mechanisms of obesity-associated low testosterone, and its reversal after weight loss, are not known,” Dhindsa said. “Inflammation and insulin resistance probably play major roles, but further research is needed.”
For more information:
Paresh Dandona, MD, PhD, can be reached at dandona@buffalo.edu.
Sandeep Dhindsa, MD, can be reached at sandeep.dhindsa@health.slu.edu.
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