Testosterone is a male reproductive hormone. As a boy reaches puberty, testosterone causes the development of secondary sex characteristics, such as male pattern body and facial hair, a deep voice, growth of the penis and testicles and increased muscle mass. Females have small amounts of testosterone in their bodies as well. The amount of testosterone in the human body begins to decrease with age. This decrease in the hormone may cause symptoms in men and women, such as a reduced interest in sex. Increased levels of testosterone may cause additional problems, such as male characteristics in females and testicular cancer for males.
Testes
The testes are two glands, also referred to as testicles, that sit inside the scrotum. In addition to sperm production, the testes produce most of the testosterone for the male body. Males may experience a delay in puberty due to the testes not producing enough testosterone. This dysfunction, also referred to as hypogonadism, is often treatable with hormone replacement therapy. As a man ages, the testes may naturally stop producing testosterone at the same rate as a young man. The decrease in testosterone by the testes can cause symptoms such as a decreased sex drive and difficulty obtaining or sustaining an erection, according to Medline Plus.
Ovaries
The ovaries produce the majority of testosterone in females. The ovaries are a pair of organs that produce and release eggs for fertilization. Testosterone in females increases sex drive and contributes to sexual function. Like men, women naturally decrease the production of testosterone later in life. The ovaries decrease production, especially as a woman enters menopause. Some females may produce more testosterone than usual and can begin to experience male characteristics, such as a condition called hirsutism, which is the development of dark, coarse hair on the face, chest and back, according to the Mayo Clinic.
Adrenal Glands
While the testes and the ovaries produce the majority of testosterone for the male and female bodies, the adrenal glands also produce small amounts of this steroid hormone. Sitting on top of the kidneys, these triangular-shaped endocrine glands produce several hormones, including testosterone. Conditions affecting the adrenal glands may cause an increased amount of testosterone in the body. Excessive testosterone produced by these glands may cause conditions such as premature puberty, male characteristics such as a deep voice in females and high blood pressure in males.
