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Bariatric surgery reverses hypogonadism in men with severe obesity
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Men with severe obesity and hypogonadism who underwent Roux-en-Y gastric bypass surgery or sleeve gastrectomy saw increases in total testosterone and sex hormone-binding globulin levels at 1 month and 6 months after surgery, according to recent findings.
“Male obesity-associated secondary hypogonadism is prevalent in extremely obese men and can be reversed with weight loss after bariatric surgery,” Patchaya Boonchaya-anant, MD, clinical instructor in Internal Medicine at Chulalongkorn University, told Endocrine Today. “In our study, the testosterone levels improved significantly, even though the patients were still quite obese at 6 months after bariatric surgery. This suggests that not only the weight loss, but also bariatric surgery itself, may have an effect on testosterone levels.”
Boonchaya-anant and colleagues analyzed data from 29 men without a previous diagnosis of hypogonadism, pituitary disease or chronic kidney or liver disease who were referred to a bariatric and metabolic institute at King Chulalongkorn Memorial Hospital in Thailand for weight-loss surgery (mean age, 31 years; mean BMI, 56/8 kg/m²; 24.1% had type 2 diabetes). Within the cohort, 15 men underwent Roux-en-Y gastric bypass surgery; 14 men underwent sleeve gastrectomy. Patients provided blood samples at baseline and at 1 and 6 months after bariatric surgery to measure total testosterone, SHBG, estradiol, adiponectin and leptin; calculated free testosterone was determined from total testosterone, SHBG and albumin levels using the Vermeulen equation.
At baseline, 16 men (55.2%) had low total testosterone levels (< 10.4 nmol/L) and low calculated free testosterone levels (< 225 pmol/L); six men (20.7%) had only low total testosterone levels; seven men (24.1%) had normal total testosterone and calculated free testosterone levels.
Researchers found that total testosterone increased from baseline at both 1 and 6 months after bariatric surgery (P .001 for both). At 6 months, only five men (17.2%) had low total testosterone and calculated free testosterone levels; six men (20.7%) had low total testosterone; seven men (24.1%) had low calculated free testosterone levels. At 6-month follow-up, 22 men (75.9%) had both normal total testosterone and calculated free testosterone levels, according to researchers.
SHBG levels increased 1 month after surgery (P .001), but no change was observed in SHBG between 1 and 6 months after surgery (P = .043). Researchers did not observe changes in estradiol levels at 1 or 6 months after surgery; leptin levels decreased and adiponectin levels increased after surgery.
Researchers also found that the increase in total testosterone at 1 month after surgery correlated with the increase in SHBG (r = 0.472; P = .042), but not with changes in body weight, BMI, estradiol adiponectin or leptin.
“Remarkably from our study, the increases in [total testosterone] and SHBG levels occurred early at 1 month after surgery during the caloric restriction phase while most patients can take in less than 1,000 calories per day and the weight loss occurs rapidly,” the researchers wrote. “SHBG level is known to be inversely correlated with insulin resistance and is a predictor of the risk of type 2 diabetes. The low SBHG levels seen in obese men at baseline are likely due to the high levels of insulin resistance, and the increase in SHBG seen during the first month after bariatric surgery likely reflects the decrease in insulin resistance with rapid weight loss and caloric restriction.” – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Ahmad O. Hammoud
Obesity is a known risk factor for hypogonadism in men. The main mechanism is thought to be the increased aromatization of testosterone to estradiol resulting in a negative feedback on the hypothalamic-pituitary axis. The decline of sex-hormone-binding globulin related to obesity and insulin resistance is also a contributing factor. In this study, weight loss through bariatric surgery was effective in normalizing testosterone levels in the majority of patients. The lack of change in estradiol level is somehow unexpected but can be explained by the research conducted by our group showing that in a subset of obese men, the polymorphism in the aromatase enzyme can blunt the relation between weight/weight loss and estradiol levels.
Disclosure: Hammoud reports no relevant financial disclosures.
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