What is testosterone?
Testosterone is produced by the gonads (by the Leydig cells in testes in men and by the ovaries in women), although small quantities are also produced by the adrenal glands in both sexes.
Testosterone is linked to many of the changes seen in boys during puberty. It also regulates the secretion of luteinising hormone and follicle stimulating hormone.
The majority of testosterone produced in the ovary is converted to the principle female sex hormone, oestradiol.
When a man has low testosterone, or hypogonadism, he may experience:
Over time, these symptoms may develop in the following ways:
- loss of body hair
- loss of muscle bulk
- loss of strength
- increased body fat
Chronic, or ongoing, low testosterone may lead to osteoporosis, mood swings, reduced energy, and testicular shrinkage.
Causes can include:
- testicular injury, such as castration
- infection of the testicles
- medications, such as opiate analgesics
- disorders that affect the hormones, such as pituitary tumors or high prolactin levels
- chronic diseases, including type 2 diabetes, kidney and liver disease, obesity, and HIV/AIDS
- genetic diseases, such as Klinefelter syndrome, Prader-Willi syndrome, hemochromatosis, Kallman syndrome, and myotonic dystrophy
Too much testosterone, on the other hand, can lead to the triggering of puberty before the age of 9 years.
In women, however, high testosterone levels can lead to male pattern baldness, a deep voice, and menstrual irregularities, as well as:
- growth and swelling of the clitoris
- changes in body shape
- reduction in breast size
- oily skin
- facial hair growth around the body, lips, and chin
Recent studies have also linked high testosterone levels in women to the risk of uterine fibroids.
Testosterone imbalances can be detected with a blood test and treated accordingly.
What does testosterone do?
Testosterone and estrogen are the main sex hormones. It also supports male physical attributes such as facial hair growth, broader shoulders, and denser muscle development.
Sexual excitement is caused in part by a rise in testosterone, though other factors contribute. Testosterone levels rise and fall throughout the day.
This could mean a man has less interest in sex later in life, and possibly less firm erections as well as softer muscle tone.
Aside from aging, there are several other causes that can result in lowered testosterone. They include:
injury to the testicles
HIV or AIDS
inflammatory diseases, such as sarcoidosis or tuberculosis
Testosterone therapy for low levels
It is possible to have low levels and not experience symptoms. But if you do not have any key symptoms, especially fatigue and sexual dysfunction, which are the most common, it is not recommended you go on the therapy given the uncertainty about long-term safety.
Even if your levels are low and you have symptoms, therapy is not always the first course of action. If your doctor can identify the source for declining levels—for instance, weight gain or certain medication—he or she may first address that problem.
If you and your doctor think testosterone therapy is right for you, there are a variety of delivery methods to consider, as found in the Harvard Special Health Report Men’s Health: Fifty and Forward.