“This surgical solution to weight loss offers more than one benefit,” said senior investigator John Morton, MD, from the Stanford University School of Medicine in California.
“If you are an obese man and you have low testosterone, before you think of testosterone replacement, you should consider surgery,” he told Medscape Medical News.
A low level of testosterone can not only affect sexual function and quality of life, it is also an independent cardiac risk factor, promotes weight gain, and raises the risk for sarcopenia, said Dr Morton.
But some previous studies have demonstrated an association between testosterone replacement therapy and an increased risk for prostate cancer, he added.
The study findings were presented here at the American College of Surgeons Clinical Congress 2015.
Dr Morton and his colleagues looked at the testosterone levels of 58 obese men (mean body mass index [BMI], 44 kg/m²) before and after laparoscopic sleeve gastrectomy, performed at a single academic center from 2007 to 2014. Mean age was 47 years.
Before the procedure, approximately half the men had a serum testosterone level below 300 ng/dL.
After the procedure, and without the use of testosterone replacement, serum testosterone levels increased in all the men.
We need to get more obese men onto the operating table and away from the dining table.
At 12-month follow-up, there was a mean increase in testosterone of 312 to 415 ng/dL, and levels were in the normal range in 46 of the 58 men (79%) (P < .003; paired Student’s t test).
“Currently, only 20% of patients undergoing weight-loss surgery are men. We need to get more obese men onto the operating table and away from the dining table,” Dr Morton said. Testosterone deficiency is just another reason for obese men to undergo sleeve gastrectomy, he added.
This issue warrants further research, said study discussant James Bittner, MD, from Virginia Commonwealth University in Richmond.
At 12 months, “surgical weight loss seems to increase the proportion of men with normal testosterone levels,” he pointed out. However, “it is too early to say that low testosterone is a standalone indication for laparoscopic sleeve gastrectomy,” he told Medscape Medical News.
Why Some Low Responders?
Overall, there is a correlation between the mean postoperative increase in testosterone of 33% and the significant reduction in BMI, said Chase Palisch, a second-year medical student at Stanford, who presented the results.
The 21% of men whose testosterone levels did not normalize after surgery had a slightly higher BMI than the other men, but the difference was not significant, Palisch reported.
“We are doing more research to learn why some men did not benefit as much as the majority did in terms of testosterone increase,” he told Medscape Medical News.
Levels of dehydroepiandrosterone (DHEA), the prohormone for testosterone, did not change significantly after the weight-loss surgery, Palisch said. He speculated that as the men lost adipose tissue, testosterone was no longer converted to estrogen, so testosterone levels increased.
Implications for Prostate Cancer Screening
The investigators also measured prostate-specific antigen (PSA) and PSA mass from total plasma volume and serum PSA concentration for each man.
One year after surgery, the mean PSA level rose by 45%, from 0.76 to 1.1 ng/mL, whereas PSA mass remained constant, Palisch reported. Because plasma volumes increased significantly after surgery (P < .001), he suggested that hemodilution might be at least partly responsible for the apparently underestimated PSA concentrations in obese men before weight loss.
“Obese men may need a different screening criterion for PSA,” he said.
Dr Bittner said he agrees. “This study’s finding that morbidly obese men exhibit low levels of PSA suggests that lowering the PSA reference range to adjust for obesity may allow for earlier detection of prostate cancer in this at-risk population,” he told Medscape Medical News.
Dr Morton, Mr Palisch, and Dr Bittner have disclosed no relevant financial relationships.
American College of Surgeons (ACS) Clinical Congress 2015: Session SF02. Presented October 5, 2015.
Medscape Medical News