Testosterone replacement therapy may result in weight reduction and improvement in symptoms of metabolic syndrome, according to separate studies presented at the Endocrine Society annual meeting in Houston.
In the first study, major weight loss was an added benefit of testosterone replacement therapy for most of the testosterone-deficient patients who participated.
"The substantial weight loss found in our study—an average of 36 pounds—was a surprise," said lead author Farid Saad, PhD, of Bayer Pharma.
Although prior studies using testosterone therapy in testosterone-deficient men consistently show changes in body composition, Dr. Saad said the net effect on weight seemed unchanged in those studies. However, Dr. Saad said this study, which took place in Germany, had a longer follow-up by at least 2 years and used long-acting injections of a form of TRT (testosterone undecanoate) that is not currently available in the U.S.
The investigators restored testosterone to normal levels in 255 hypogonadal men whose average age was nearly 61 years (range, 38 to 83 years). Treatment lasted for up to 5 years, with injections given at day 1, after 6 weeks, and then every 12 weeks after that. Patients did not follow a controlled diet or standard exercise program but received advice to improve their lifestyle habits.
On average, the men weighed 236 pounds before beginning testosterone treatment and 200 pounds after treatment, the authors reported. Weight loss was reportedly continuous, with an average reduction in body weight ranging from about 4% after 1 year of treatment to more than 13% after 5 years.
In a second study, TRT significantly improved symptoms of metabolic syndrome associated with testosterone deficiency in men.
"When indicated, testosterone treatment is both essential and safe in elderly patients with symptomatic late-onset hypogonadism," said lead author Aksam A. Yassin, MD, PhD, of the Institute of Urology & Andrology in Norderstedt-Hamburg, Germany. "Further analysis is needed to confirm if our findings are due to a direct effect of restoring physiologic testosterone levels."
Specifically, investigators found that the prevalence of metabolic syndrome dropped from 56% to 30% after 57 months of treatment with TRT to regulate hormone levels. In addition, triglycerides, blood sugar levels, and blood pressure significantly decreased, while the average waist circumference shrank by 11 cm.
Beginning in 2004, investigators collected data from 261 patients with late-onset hypogonadism at three centers in Germany. Patients received 1,000 mg of testosterone undecanoate on the first day of the study, at week six, and then every 3 months. At each visit, patients underwent testing of hormone levels, blood-sugar and lipid concentrations, and blood pressure. Average follow-up was 4.25 years.
"We hypothesized that long-term testosterone improves metabolic syndrome, and found that this intervention improved all three components of obesity, including waist circumference, weight, and body mass index; diabetes control; poor lipids profile; and blood pressure," Dr. Yassin said.
Bayer Pharma partially funded the weight loss study in its final 2 years and supported data entry for the metabolic syndrome study.