Australian research suggests that when testosterone is injected into the liver in small doses, it stimulates protein synthesis. Researchers believe this could prevent muscle loss and atrophy (muscle wasting) and promote muscle growth. This could be the first step in developing an effective treatment for men and women to prevent muscle wasting associated with chronic disease and aging.

Researchers from Sydney's Garvan Institute of Medical Research, a biomedical research foundation focused on gene, molecular, and cellular processes in health and disease, published their findings in the European Journal of Endocrinology. Dr. Vita Birzniece and Professor Ken Ho found that when small doses of the male hormone testosterone, in pure crystallized form, was taken in small oral dosages each day, it prevented protein wasting in healthy postmenopausal women.

Birzniece and Ho found that when testosterone was injected or administered through a gel or skin patch in larger doses directly into major organs, including the brain, side effects occurred. Other unwanted side effects such as aggressive behavior, heightened libido, heart damage, and for women, facial hair and a deeper voice, were direct results of the testosterone injections.

Smaller doses given orally when absorbed into the gut and straight into the liver, however, avoids the tissue or organ exposure. There is no spillover into the blood stream or other organs, which means the testosterone remains contained in its intended location, the liver. This is a new approach to stimulating muscle growth in order to increase muscle strength.

"This is a great advantage because it avoids the unpleasant behavioral effects of high doses of testosterone injected into the bloodstream and the masculinizing effects in women," Ho said.

Testosterone is the male sex hormone produced by the testes, which the body naturally uses to help the growth of testes, body hair, muscles, bones, voice deepening, and sexual maturation during pubescent years, ages nine to 14. Women have been injecting testosterone to increase their sex drive and accumulation of muscle mass for years, but there are many physical signs of testosterone injectors. Supplementing testosterone by injections to increase athletic performance is harmful and comes with many side effects for both genders. Tablets, however, could provide entirely useful medical benefits.

"This is really hopeful, because if we can see the same effect on protein metabolism at this stage, we believe it will translate into the same increase in muscle mass that we see from testosterone delivered systematically, yet avoiding all the unpleasant side effects," said Birzniece.

Researchers need to conduct further research to understand the safety and benefits of testosterone tablets for patients suffering from chronic diseases. The next step will be to recruit men with below average testosterone levels, frail people, and those with kidney failure in order to see if a placebo-controlled study will have the same effect.

"If we can reduce muscle wasting in frail elderly people, this would prevent many falls, and therefore osteoporotic fractures," said Ho.

Source: Birzniece V, Umpleby MA, Poljak A, Handelsman DJ, Ho KKY. Oral low-dose testosterone administration induces whole-body protein anabolism in postmenopausal women: a novel liver-targeted therapy. European Journal of Endrocrinology. 2013.