BETHESDA, MD. — Testosterone replacement therapy in hypogonadal men appears to significantly improve trabecular bone architecture, according to the results of a small study.
Findings from previous studies suggest that testosterone replacement therapy increases bone mineral density in hypogonadal men, but none of these investigations looked at the effect of the hormone on trabecular architecture.
Maria Benito, M.D., reported at a meeting on bone quality the improvements seen in trabecular architecture in 10 hypogonadal men (median age 51 years) after 2 years of testosterone gel (AndroGel) therapy.
Each patient applied 5 g of a transdermally absorbed gel once per day and then received doses titrated to keep their serum testosterone level within the normal range of 400–900 ng/dL. The men increased their serum testosterone level from a mean of 88 ng/dL at baseline to 468 ng/dL after 2 years, said Dr. Benito of the division of endocrinology, diabetes, and metabolism at the University of Pennsylvania, Philadelphia.
Using micro MRI scans of the distal tibia taken at baseline, 6, 12, and 24 months, Dr. Benito and her colleagues matched architectural parameters in the images from each subject at each time point to ensure that the same volume was analyzed each time. They measured the ratio of surface voxels (representing trabecular plates) to curve voxels (representing trabecular rods) and the ratio of topologic parameters expected to increase during trabecular deterioration to those expected to decrease (the topologic erosion index).
After 24 months of treatment, the ratio of surface to curve voxels increased significantly by 11% while the topologic erosion index decreased significantly by 8%; both measures indicate that trabecular architecture improved. Bone mineral density also rose significantly in the L1-L4 vertebrae by 7%.
The improvement in trabecular architecture could not be attributed to body mass index or calcium intake during treatment since neither factor changed substantially. Testosterone's effect on trabecular architecture suggests that it may exert an anabolic effect on bone, she said.
Men with a calcium intake of less than 750 mg per day, a history of disease, or on medications that could affect bone, were excluded from the study, Dr. Benito said at the meeting, sponsored by the National Institute for Arthritis, Musculoskeletal, and Skin Diseases and the American Society for Bone and Mineral Research.
Solvay Pharmaceuticals provided the AndroGel used in the study. Dr. Benito had no financial conflicts of interest to report.