Low testosterone is a condition affecting five million American men, according to the National Institutes of Health. The condition becomes more common with age, affecting 39 percent of men over age 35. One in five men experiences "Low T" in their 60s, while by age 70, the percentage jumps to 30 percent, the Urology Care Foundation points out. More than half of men in their 80s suffer from Low T.
This important hormone is integral to a man's health. There are several warning signs of Low T. Three common ones are decreased sex drive, low sperm count, and depression. Understanding the warning signs of low testosterone and why levels decline can help men decide whether to seek treatment.
Decreased Sex Drive
The most commonly recognized warning sign of Low T is decreased interest in sex or low libido. When testosterone levels are low, they don't trigger brain receptors to produce the nitric oxide that's essential in jump-starting sexual desire.
According to J. Francois Eid, M.D., clinical associate professor of urology at the Weill-Cornell Medical College of Cornell University, while the link between libido and testosterone is well-established, there's no strong association between erectile function and Low T. Low T will affect a man's mood, but it doesn't preclude a man from experiencing erections, he noted.
Erectile dysfunction results from vascular issues causing decreased blood flow to the penis. When ED surfaces, erection quality and quantity suffer, leading to decreased interest in sex. The lack of interest in sex too often leads to an erroneous Low T diagnosis, according to Eid. But testosterone replacement therapy can do more harm than good when treating ED, so it's important to understand whether ED or Low T is the culprit when interest in sex wanes.
Eid also said it's important not to mistake the normal testosterone range among men -- 300 to 1,200 ng/dl -- as a "high-low" scale.
Low Sperm Count
Low T is predominantly an issue for older men, but younger men sometimes experience the problem as well. A younger man with a low sperm count often gets the news when fertility issues arise. Through a semen analysis, doctors can determine whether a low sperm count is affecting fertility. Low sperm count is defined as less than 15 million sperm per milliliter of semen.
Testosterone is an essential hormone for producing sperm. Its scarcity can be due to primary or secondary hypogonadism. Primary hypogonadism results from testicular causes, while secondary hypogonadism results from the failure of the brain, specifically the pituitary gland or the hypothalamus, to produce sufficient luteinizing hormones that instruct the testes to produce testosterone. Reasons for primary hypogonadism include:
malfunctions resulting from uncorrected undescended testicles
damage to the testes from mumps
chemotherapy or radiation damage
A 2008 study reported in the Archives of General Psychiatry established a link between low testosterone levels and depression. The research found older men with abnormally low free testosterone levels were 271 percent more likely than men with normal testosterone levels to experience depression independent of factors such as age, education level, smoker status, poor health, and obesity. The findings suggest a causal relationship between low free testosterone and depression in older men, said researcher Osvaldo P. Almeida, MD, PhD, director of research at the Western Australian Centre for Health and Ageing. He said scientific evidence suggests "testosterone may increase the bioavailability of serotonin and noradrenaline in the brain and this could explain its antidepressogenic effect."
Decreased sex drive, low sperm count, and depression do not necessarily mean testosterone levels are low, but it's a possibility to consider, particularly when multiple warning signs are present.