What Is Testosterone and Why Does It Decline?
Testosterone is a hormone. It’s what puts hair on a man’s chest. It’s the force behind his sex drive.
During puberty, testosterone helps build a man’s muscles, deepens his voice, and boosts the size of his penis and testes. In adulthood, it keeps a man’s muscles and bones strong and maintains his interest in sex. In short, it’s what makes a man a man (at least physically).
After age 30, most men begin to experience a gradual decline in testosterone. A decrease in sex drive sometimes accompanies the drop in testosterone, leading many men to mistakenly believe that their loss of interest in sex is simply due to getting older.
“Some say it’s just a part of aging, but that’s a misconception,” says Jason Hedges, MD, Ph.D., a urologist at Oregon Health and Science University in Portland. A gradual decline in testosterone can’t explain a near-total lack of interest in sex, for example. And for Hedges’ patients who are in their 20s, 30s, and early 40s and having erectile problems, other health problems may be a bigger issue than aging.
Low Testosterone: How Low Is Too Low?
The bottom of a man’s normal total testosterone range is about 300 nanograms per deciliter (ng/dL). The upper limit is about 800ng/dL depending on the lab. A lower-than-normal score on a blood test can be caused by a number of conditions, including:
- Injury to the testicles
- Testicular cancer or treatment for testicular cancer
- Hormonal disorders
- Chronic liver or kidney disease
- Type 2 diabetes
Some medicines and genetic conditions can also lower a man’s testosterone score. Aging does contribute to low scores. In some cases, the cause is unknown.
A low score does not always translate to symptoms, Mezitis says, “but we often find something that’s off when we see scores of 200 or 100 ng/dL.”
Hedges agrees and warns that even if a man does not have symptoms, he may be well advised to seek treatment. Low testosterone scores often lead to drops in bone density, meaning that bones become more fragile and increasingly prone to breaks.
“That’s something I would want to have a conversation about,” Hedges says. “Bone density issues are not always apparent.”
Low Testosterone Treatment
Having a gradual decline in your testosterone level as you age is to be expected. Treatment is sometimes considered if you’re experiencing symptoms related to low testosterone.
If a young man’s low testosterone is a problem for a couple trying to get pregnant, gonadotropin injections may be an option in some cases. These are hormones that signal the body to produce more testosterone. This may increase sperm count. Hedges also describes implantable testosterone pellets, a relatively new form of treatment in which several pellets are placed under the skin of the buttocks, where they release testosterone over the course of about three to four months. Injections and nasal gels may be other options for some men.
“If their symptoms are truly due to low testosterone, patients tell me that within a few weeks they notice a significant difference, though sometimes it is not too dramatic,” Hedges says. “Sex is better, depression is better — you can see it directly and quickly.”
There are also risks. Testosterone treatment can raise a man’s red blood cell count as well as enlarge his breasts. It can also accelerate prostate growth. Men with breast cancer should not receive testosterone
Testosterone treatment usually is not advised for men with prostate cancer. Hedges says some of the associations between testosterone replacement therapy and prostate health are currently being challenged. In his practice, he does offer testosterone treatment to men who have been treated for prostate cancer.
“The take-home [message] is treatment is safe as long as you get careful monitoring,” Hedges says. “If there are known issues, patients should be treated by a specialist.”