Testosterone replacement therapy for men

For decades, older women have taken hormone replacements to replenish estrogen and progesterone levels lost to aging.

More recently, testosterone (the most important male hormone) supplements have been used by aging men to improve their muscle mass, bone strength, libido and quality of life. In 2002, the number of elderly American men taking testosterone replacement therapy was nearly 819,000, and the number is growing. The increased use has occurred despite the fact that the cardiovascular effects of chronic testosterone treatment in aging males are largely unknown, and the safety of testosterone replacement has not been evaluated.

A team of researchers has been using an animal model to investigate potential links between testosterone supplements and cardiovascular and renal disease. The team, comprised of Radu Iliescu, Licy L. Yanes, Julio C. Sartori-Valinotti, and Jane F. Reckelhoff, is affiliated with the University of Mississippi Medical Center's Department of Physiology and Biophysics, Jackson, MS. Their most recent study and an overview of data from other human and animal studies is part of the upcoming conference, Sex and Gender in Cardiovascular-Renal Physiology and Pathophysiology. The meeting, sponsored by The American Physiological Society (APS; http://www.The-APS.org), is being held August 9-12, 2007 at the Hyatt Regency Austin on Town Lake, Austin, TX.

The team is presenting its work entitled, “Testosterone Supplements Promote Renal Injury and Exacerbate Hypertension in Aging Spontaneously Hypertensive Rats (SHR),” in which spontaneously hypertensive rats were used as a model for genetic hypertension.

Three groups of rats were used: intact, gonadectomized (at eight months of age), and testosterone-supplemented rats. Testosterone supplements were administered chronically via pellets and rats were monitored until 13 months of age. Blood pressure was measured at the end of the experiment via indwelling arterial catheters inserted into conscious, freely moving rats. Urine was collected for two hours and urinary protein excretion was determined.

The researchers found that blood pressure was significantly higher in testosterone-supplemented male SHR as compared with intact rats, whereas castration did not alter blood pressure levels. Testosterone supplemented SHR excreted more urinary protein than intact rats, and castration reduced proteinuria (urinary protein).

The results suggest that testosterone supplementation of aging male SHR promotes renal injury and thereby exacerbates hypertension. The results also show that removal of endogenous androgens later in life (eight months) prevents the development of hypertensive renal injury without altering existing hypertension levels.

The study is part of the researchers' ongoing project to investigate the effects of testosterone-supplementation in animal models of disease that mimic the characteristics of the human male population that currently receive testosterone supplements. They are currently testing the hypotheses that the natural decrease in testosterone brought on by aging may affect the progression of pre-existing cardiovascular/renal disease.

The American Physiological Society (APS) has been an integral part of the scientific discovery process since it was established in 1887. Physiology is the study of how molecules, cells, tissues and organs function to create health or disease.