Testosterone deficiency, also known as hypogonadism, occurs when the body does not produce enough testosterone, a hormone crucial for various bodily functions. This condition can affect both men and women, though it is more commonly discussed in men. Symptoms may include fatigue, reduced libido, and decreased muscle mass. Causes of testosterone deficiency can vary and may include aging, certain medical conditions, or injuries to the testes or pituitary gland. Diagnosis typically involves blood tests to measure hormone levels, and treatment options may include hormone replacement therapy or lifestyle changes to improve overall health.