How is testosterone produced?
Testosterone is a hormone produced primarily in the testicles in men and in smaller amounts in the ovaries in women. It plays a crucial role in regulating sex differentiation, producing male sex characteristics, spermatogenesis, and fertility.
The production of testosterone is controlled by signals sent from the brain to the pituitary gland at the base of the brain. The pituitary gland then relays signals to the testes to produce testosterone. This process is regulated by a “feedback loop” that closely monitors hormone levels in the blood1.
Testosterone has many important functions throughout life. During fetal development, it triggers the development of male internal and external reproductive organs. During puberty, it is responsible for many of the changes seen in boys such as an increase in height, body and pubic hair growth, enlargement of their penis and testes and an increase libido (sex drive). In adulthood, testosterone helps maintain men’s bone density fat distribution muscle strength and mass facial and body hair red blood cell production sex drive sperm production2.

The pathophysiology of hypogonadism
Low testosterone (low-T) is a condition where there is underproduction or lack of production of testosterone in men and women. Causes of low-T include chronic medical conditions such as diabetes, infections, obesity, or other hormonal conditions.
Testosterone is a hormone that affects emotional regulation. Low levels of testosterone can lead to feelings of sadness or depression and can affect memory, concentration, motivation and self-confidence4.
Low-T can be treated with testosterone replacement therapy3. It’s important to see your healthcare provider if you have symptoms of low-T so that they can help you find the cause and get appropriate treatment.
The pituitary gland and low testosterone
The pituitary gland plays a key role in regulating testosterone levels. It releases luteinizing hormone (LH) which travels to the testicles and stimulates the production and release of testosterone1. The pituitary gland also releases follicle-stimulating hormone (FSH) which causes sperm production5.
Any issue with the testicles, hypothalamus or pituitary gland can cause low testosterone (male hypogonadism). For example, a pituitary tumor or other type of brain tumor located near the pituitary gland may cause testosterone or other hormone deficiencies. Also, treatment for a brain tumor, such as surgery or radiation therapy, can affect the pituitary gland and cause hypogonadism6.
In conclusion, testosterone plays a crucial role throughout life by regulating sex differentiation producing male sex characteristics spermatogenesis and fertility.
What medical conditions can affect testosterone levels?
There are several medical conditions that can affect testosterone levels. Men can experience a drop in testosterone due to conditions or diseases affecting the testes such as direct injury, castration, infection, radiation treatment, chemotherapy or tumors7. Certain inflammatory diseases such as sarcoidosis, histiocytosis and tuberculosis involve the hypothalamus and pituitary gland and can affect testosterone production. HIV/AIDS can also cause low levels of testosterone by affecting the hypothalamus, pituitary gland and testes8.
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