Testosterone replacement therapy is a hormone therapy used to address abnormally low levels of testosterone. Low testosterone is also called hypogonadism. There are many forms of TRT available, including transdermal (skin patch), gels, mouth patches, and injections or implants. The goal of testosterone replacement therapies is to restore blood concentration levels of testosterone and improve symptoms of low T, such as mental health and sex drive.
With male hypogonadism, the body generates insufficient levels of testosterone. A patient may receive a diagnosis of hypogonadism if testosterone levels measure below 300 ng/dL after several tests and they have additional symptoms, such as:
Estimates suggest that hypogonadism affects around 39% of men aged 45 years or older.
Low testosterone levels may be caused by an issue with the testicles, which is referred to as primary hypogonadism. The other type, called secondary hypogonadism, occurs because of a problem with the parts of the brain responsible for starting testosterone production. TRT may be used to help restore testosterone levels and relieve symptoms in both types.
While testosterone is an important hormone for fertility, TRT can harm sperm production. Adding testosterone to the body through TRT blocks the release of follicle stimulating hormone (FSH) and luteinizing hormone (LH). In turn, the reduced LH levels lead to significantly lower intratesticular testosterone levels, hurting sperm production and therefore fertility. In fact, testosterone can be used for male contraception. Research indicates that using testosterone can result in azoospermia (no sperm in the ejaculate) within 4 months in 65% of men who started with normal sperm counts.Still, the effects of TRT generally aren’t permanent. Once TRT ceases, sperm production usually returns to normal levels after around 1 year, or up to 2 years in some men. The restoration of fertility, however, is not always guaranteed.