Testosterone is a steroid hormone primarily produced in men's testes and women's ovaries. It is the primary hormone causing secondary sexual characteristics in men, such as increased muscle mass, bone mass, hair growth and sex drive. Male testosterone levels commonly decline after the age of 40, at an average rate of 1 to 2 percent yearly, according to "Human Biochemistry and Disease." Lack of testosterone, defined as less than 300 ng/dL of blood, affects men's health and causes characteristic symptoms.
Sexual Dysfunction
In males, symptoms of lack of testosterone depend upon age. Low testosterone in a male fetus leads to underdevelopment of the penis and scrotum, sometimes to the extent of appearing ambiguous or androgynous.
Lack of testosterone before or during puberty leads to lack of sexual maturation, such as underdeveloped muscles, failure of the voice to deepen, reduced body hair, growth of male breasts and failure of the penis and testicles to enlarge.
In adulthood, lack of testosterone leads to decreased libido, erectile dysfunction, reduced sexual endurance, and potentially, infertility. Penile muscles and tissue contain androgen receptors, and without testosterone, are prone to atrophy. During middle-age, men can lose up to two percent of testicular function yearly, which is the main cause of reduced testosterone production, as cited by "Professional Guide to Diseases."
Other Physical Changes
Lack of testosterone in adulthood can also lead to loss of pubic hair, decreased muscle mass, decreased muscle strength, reduced bone mass, potentially leading to osteoporosis, and increased body fat. A 2008 article on ScienceDaily.com reports that research suggests that genes that control percentage of body fat are also responsible for circulating levels of testosterone in men. The lower abdomen is the most common area for fact accumulation in those with low testosterone levels.
Mood Changes
Lack of testosterone in male adults often has profound effect on mood. In addition to profound loss of sexual desire, other mood changes include irritability, depression, fatigue and difficulty with concentration. These mood changes can lead to memory loss and sleep difficulties, which contributes to additional lack of energy. A 2010 Chinese study published in the "Journal of Alzheimer's Disease" found that low levels of testosterone in Chinese men was linked to higher risks of developing Alzheimer's disease.
Female Symptoms
While lack of testosterone is usually thought of as a male problem, who produce 10 times more of the hormone, low levels occur in females and cause significant problems also. Female symptoms of low testosterone include hot flashes, irritability, loss of sexual desire and sleep disturbances, much like their male counterparts. Loss of muscle mass, decreased bone density and loss of body hair may also be seen in females.
References
- "Human Biochemistry and Disease"; Gerald Litwack; 2008
- "Professional Guide to Diseases: Ninth Edition"; Springhouse Publishing; 2009
- ScienceDaily.com: "Testosterone And Body Fat Are Controlled By The Same Genes"; August 6, 2008
- "Journal of Alzheimer's Disease"; Bioavailable Testosterone Predicts a Lower Risk of Alzheimer's Disease in Older Men; L.W. Chu et al.; August 2010
