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An Overview of the Testes

Testes secrete the male hormone testosterone

Testes Essentials

  • The testes secrete testosterone, which is necessary for proper physical development in boys.
  • In adulthood, testosterone maintains libido, muscle strength, and bone density.
  • Disorders of the testes are caused by too little testosterone production.
The testes (or testicles) are a pair of sperm-producing organs that maintain the health of the male reproductive system. The testes are known as gonads. Their female counterpart are the ovaries.
In addition to their role in the male reproductive system, the testes also have the distinction of being an endocrine gland because they secrete testosterone—a hormone that is vital to the normal development of male physical characteristics.
Anatomy of the Testes
The testes are twin oval-shaped organs about the size of a large grape. They are located within the scrotum, which is the loose pouch of skin that hangs outside the body behind the penis. While this location makes the testes vulnerable to injury (they have no muscles or bones to shield them), it provides a cooler temperature for the organs. A cooler environment is necessary for healthy sperm production.
Testosterone: The Hormone of the Testes
Testosterone is necessary for proper physical development in boys. It is the primary androgen, which is the term for any substance that stimulates and/or maintains masculine development. During puberty, testosterone is involved in many of the processes that transition a boy to manhood, including:
  • Healthy development of male sex organs
  • Growth of facial and body hair
  • Lowering of the voice
  • Increase in height
  • Increase in muscle mass
  • Growth of the Adam’s apple
The importance of testosterone is not limited to puberty. Throughout adulthood, the hormone is integral in a variety of functions, such as:
  • Maintaining libido
  • Sperm production
  • Maintaining muscle strength and mass
  • Promoting healthy bone density
Testosterone Production
The hypothalamus and pituitary gland control how much testosterone the testes produce and secrete.
The hypothalamus sends a signal to the pituitary gland to release gonadotrophic substances (follicle stimulating hormone and luteinizing hormone). Luteinizing hormone (LH) stimulates testosterone production. If too much testosterone is produced, the hypothalamus alerts the pituitary gland to make less LH, which tells the testes to decrease testosterone levels.
Disorders of the Testes: Hypogonadism
Hypogonadism is a testicular disorder associated with low testosterone. Having testosterone levels that are too low causes a variety of problems, including:
  • Decreased sex drive
  • Diminished muscle mass
  • Low sperm count (reduced fertility)
  • Loss of body hair
There are two types of hypogonadism—primary and secondary. Primary refers to a defect with the testicles, and secondary involves a problem in the pituitary gland that indirectly affects testosterone production.
The condition may be caused by many things and is most commonly the result of:
  • Aging
  • Defects in the pituitary and/or hypothalamus, such as pituitary tumors (which adversely affect the pituitary’s ability to function normally) and high prolactin levels (too much of the hormone causes a drop in testosterone levels)
  • Medications
  • Testes-based conditions, such as severe injury, and radiation or chemotherapy, can all deplete testosterone levels
The testes play a vital role not only in the male reproductive system but in the endocrine system as well. The release of the hormone testosterone is integral to the healthy development of male physical characteristics.