What Are the Options for Testosterone Replacement Therapy?
A deficiency of the naturally occurring steroid hormone testosterone can cause a number of physiological changes in men. In testosterone replacement therapy, doctors administer synthetic versions of the hormone to mitigate or reverse these effects. Pharmaceutical companies manufacture testosterone in a variety of forms, each of which has benefits and side effects.
What Is Testosterone?
Testosterone is a naturally occurring steroid hormone that produces muscle and bone growth, and causes masculine characteristics. Deficiencies can cause lower libido, changes in bodily composition (more fat, less muscle), osteoporosis, fatigue, depression and erectile dysfunction.
What Is Replacement Therapy?
In men, natural production of testosterone peaks between the ages of 18 to 25, and after 25, declines at a rate of about two percent each year. This can lead to some of the symptoms of testosterone deficiency listed above.
To counteract this effect of aging in men and enhance quality of life, doctors have begun to prescribe testosterone replacement therapy. Men over 30 who experience any of the symptoms of testosterone deficiency should consult their doctor.
Doctors may also prescribe testosterone replacement therapy to men who are experiencing hypogonadism (low sperm production), or who have testosterone deficiencies caused by testicular injury or infection, kidney failure, chemotherapy, pituitary or hypothalamic injury or trauma, congenital conditions, sarcoidosis (a disease that inflames the lung and organ tissue), or cirrhosis of the liver.
In theory, the regimen used in testosterone replacement therapy should attempt to achieve the levels that would be produced naturally before a deficiency. On average, men produce 4 to 7 mg of testosterone each day, mostly in the morning.
Because it is difficult to accurately mimic the circadian pattern of natural production, doctors instead shoot to optimize testosterone administration and dosage by the achievement of desired physiological benefits. These benefits might include increases in bone density and/or muscle mass (accompanied by a concomitant decrease in body fat), improvement of mental health, elimination of fatigue, an enhanced sense of well-being, the restoration of libido and proper erectile function.
According to Tulane University Medical Center’s Doctor Wayne J.G. Hellstrom, about one-third of U.S. men receiving testosterone therapy take oral testosterone. These can be swallowed as pills or tablets (Andriol, Proviron, fluoxymesterone) or absorbed in the mouth by an adhesive strip of the drug held against the gums (Striant). Many of these versions are modified by the addition of a methyl group (to make it more difficult for the liver to break them down and prolong their effects), which increases the hepatotoxicity of these pills (increases the likelihood that they will damage the liver).
According to Hellstrom, intra-muscular injections provide a safe means of delivering testosterone during replacement therapy. These oil-based injectable versions (such as testosterone enanthate) can be modified by the attachment of an ester group, which prolongs their activity in the body.
Typical dosages range from 50 to 400 mg, injected once every two or three weeks. Pharmaceutical companies also make an aqueous version (testosterone suspended in water), which must be injected more frequently. The frequency of testosterone injections can inconvenience some patients, and it can also result in fluctuations of sexual desire, mood and energy levels.