SAN DIEGO, CA - The risk of osteoporosis (bone fracture) in women is highly recognized by the public. Less appreciated is the fact that the disorder also occurs in men. Some two million males have been diagnosed with osteoporosis and another three million are at risk.
Gender-based hormones and age are thought to be major factors behind bone fractures in both sexes. Women with low levels of estrogen and men with low levels of the testosterone are known to be at risk. Low levels of gender hormones can lead to diminished bone mineral density (BMD; also known as bone mass). Reduced bone density or bone mass means there is less cushioning to protect the bone from cracking in a slip or fall.
For this reason, testosterone replacement therapy (TRT) is the standard of care used to improve bone strength and muscle mass in males. However, TRT use has been the subject of some controversy. Continuous testosterone use has been associated with prostate cancer and high red blood cell levels, and its other effects are not fully known.
In one of the first clinical trials involving men over 60-85 years of age, researchers' preliminary results indicate that testosterone treatment for five months has a positive effect on the bone markers of older men. This is the first known study to report on the impact of bone metabolism based on dosing schedules.
Presentation at the 121st Annual Meeting of the American Physiological Society
The study was conducted by E. Lichar Dillon, Randall J. Urban, James A. Angel, Shanon L. Casperson and Melinda Sheffield-Moore, all of the Department of Internal Medicine, University of Texas Medical Branch, Galveston, TX; and Douglas Paddon-Jones of the Department of Rehabilitation Sciences and Physical Therapy, the University of Texas Medical Branch. Their study was funded in part by the National Institutes of Health (NIH) and is entitled Continuous Testosterone Administration for Five Months Reduces Markers of Bone Turnover in Older Men. Dr. Dillon is presenting the team's preliminary findings at the 121st Annual Meeting of the American Physiological Society (APS; www.the-APS.org/press), part of the Experimental Biology 2008 scientific conference.
Thirteen older men between 60 - 85 years have thusfar participated in the study. Testosterone levels ranged between 200-500 nanograms (ng) of testosterone per deciliter of blood (dL) at the time of enrollment. (Normal limits are considered 250-800.) Each was enrolled in one of three double-blinded groups: (1) those receiving continuous weekly intramuscular injections of testosterone (100 mg testosterone-enanthate) for the entire five month period (TE; n=4); (2) those receiving weekly testosterone every other month (one month of weekly testosterone/one month of weekly placebo; MO; n=4); or (3) those receiving a weekly placebo for the entire five month period (PL; n=5).
The participants visited the clinic weekly for either scheduled treatment injections or placebos. Volunteers received a baseline whole-body Dual Energy X-Ray Absorptiometry (DEXA) scan at the beginning and end of the study. Dietary records were obtained and analyzed at month zero, month three and month five. Fasting blood samples were collected at regular intervals throughout the study to examine serum markers of bone metabolism.
The Preliminary Study Results
The research team found that:
- testosterone administration appears to reduce bone turnover, perhaps closing the gap between resorption and formation
- thus far, the impact on bone mineral density are unclear but may become more apparent as the study progresses.
- the effects of testosterone on long-term bone metabolism are unclear, but are expected to have at least a protective effect on existing bone mass over time by preventing unwanted increases in bone turnover that are frequently associated with osteoporosis. Osteoporosis is often associated with high bone turnover (increases in bone resorption as well as in bone formation) which results in decreased BMD.
According to Dr. Dillon, the study's first author, "These preliminary data show beneficial effects of testosterone therapy on bone turnover markers in older men with low-to-normal testosterone concentrations using both continuous and monthly cycled testosterone replacement." He added, "The effects of sex hormones on markers of bone formation are complex, but this is an important step in understanding how the process works."
Physiology is the study of how molecules, cells, tissues and organs function to create health or disease. The American Physiological Society (APS; www.The-APS.org/press) has been an integral part of this discovery process since it was established in 1887.
NOTE TO EDITORS: The APS annual meeting is part of the Experimental Biology 2008 (EB '08) gathering and will be held April 5-9, 2008 at the San Diego, CA Convention Center. To schedule an interview with Dr. Dillon please contact Donna Krupa at 301.634.7209 (office), 703.967.2751 (cell) or DKrupa@the-APS.org.