Testosterone production declines naturally with age. Testosterone deficiency known as TD may result from disease or damage to the hypothalamus, pituitary gland, or testicles that inhibits hormone secretion and testosterone production, and is also known as hypogonadism. Depending on age, insufficient testosterone production can lead to abnormalities in muscle and bone development, underdeveloped genitalia, and diminished virility. Testosterone is the androgenic hormone primarily responsible for normal growth and development of male sex and reproductive organs, including the penis, testicles, scrotum, prostate, and seminal vesicles. It facilitates the development of secondary male sex characteristics such as musculature, bone mass, fat distribution, hair patterns, laryngeal enlargement, and vocal chord thickening. Additionally, normal testosterone levels maintain energy level, healthy mood, fertility, and sexual desire.