Testosterone Deficiency
Overview
Approximately 39% of men over the age of 45 have low testosterone (T), clinically referred to as hypogonadism.
Low T is defined as total T levels below 300 ng/dL, according to a study published in the International Journal of Clinical Practice in 2006. Based upon this prevalence rate and the U.S. Census Bureau’s 2009 estimate that there are 48.3 million men between 45 and 75 years old, nearly 19 million men in the United States may have low T. Annually, nearly 500,000 new cases of low T are expected to be diagnosed in the United States as the male population ages according to a study published in the Journal of Clinical Endocrinology and Metabolism in 2004.
Common symptoms of low T include:
- erectile dysfunction
- reduced sex drive
- fatigue
- anemia
- difficulties concentrating
- mild depression
- muscle weakness
- increased body fat
- reduced muscle mass
There are two types of hypogonadism, secondary hypogonadism and classical hypogonadism. Secondary hypogonadism can be age-related, also referred to as late-onset hypogonadism, illness-associated or caused by some medications, such as opioid drugs used in pain management. Age-related hypogonadism, in which men lose their ability to produce adequate levels of T, typically affects males beginning at about 45 years of age. The graph below depicts the percentage of men with low T by age bracket and shows the prevalence of low T as a function of age.
Prevalence of Men with Low T Based on Age
Source: Mulligan et al., International Journal of Clinical Practice, 2006.
Low T has been associated with diseases that include metabolic syndrome, type 2 diabetes, chronic heart disease, asthma and chronic obstructive pulmonary disease. For example, about one-third of all men with type 2 diabetes are hypogonadal, according to research published in Diabetes Care in 2007. Similarly, a significant number of men with metabolic syndrome, which is a precursor to type 2 diabetes and associated with obesity, also have low T, according to research published in Journal of Andrology in 2009.
Classical, also known as primary, hypogonadism is caused by the failure of the testes to synthesize and secrete T. Causes of classical hypogonadism include Klinefelter’s syndrome, a condition in which males have an extra X sex chromosome, testicular tumors, testicular damage, varicocele, which is an abnormal enlargement of the vein in the scrotum that drains blood from the testicles, disease-associated testicular damage, including from HIV or mumps, certain systemic diseases, such as renal insufficiency, and exposure to toxins, such as alcohol in chronic excess.