From the article:
The aim of the study was to investigate the effect of surgical weight loss following sleeve gastrectomy [removement of about 75 percent of the stomach] on serum testosterone, DHEA (a precursor to testosterone), and prostate-specific antigen (PSA). This clinical study involved 24 obese male patients undergoing gastric sleeve surgery, also called sleeve gastrectomy, at Stanford Hospital. Serum testosterone, DHEA, and PSA were measured before and at three, six, and 12 months after the procedure.
The researchers found that the study group experienced a significant increase in average serum testosterone after undergoing sleeve gastrectomy. At 12 months, testosterone had increased on average from 295 to 423 ng/dL. The normal range for circulating testosterone is 300 to 1000 ng/dL. A person is diagnosed with low serum testosterone when the level drops below 300 ng/dL.
Before the procedure, 63 percent of participants had low testosterone and afterwards, only 41 percent did. The average BMI was 46 before surgery and 31 after the operation. In addition, DHEA also rose, from 12.8 to 39.6 ng/mL, and serum PSA concentration rose over 12 months from 0.62 to 0.75 ng/mL with no change in PSA mass, which is a marker for prostate cancer progression.
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“When you are obese, your fat becomes converted to estrogen, which will compete with testosterone and drive it down,” Dr. Morton said. “The nice thing about what this process does is it creates an autotransfusion of testosterone from yourself. This process occurs because you are losing weight, and therefore losing that estrogen, causing your natural testosterone stores to rise. It’s actually really helpful across the board for these patients.”