The endocrine system is one of the most complex systems in the human body. Everything is tightly regulated by various mechanisms. Testosterone release is no different. When you take testosterone from an outside source, the body will begin to produce less of its own. Understanding the mechanisms of this will help you feel more comfortable with testosterone therapy.
Testosterone Therapy
As men age, their testosterone levels begin to fall. According to the Mayo Clinic, a male's testosterone will drop about 1 percent every year after 30 years of age. Many individuals look into testosterone therapy so that their hormone levels can be normalized to levels similar to when they were younger. If a blood draw shows you have low testosterone levels, your physician may prescribe you with testosterone. This could be in the option of a patch, injection, or tablet.
Endocrine System
The endocrine system is the system of organs and glands that control the various hormones of the body. There are a variety of methods that your body uses to control the release of its hormones. One mechanism is the negative feedback loop. This system relies on the fact that once a large enough amount of a particular hormone is circulating in the body, the body will then stop making that hormone to maintain balance.
HPTA
With respect to testosterone, the hypothalamus, pituitary and testicles all play a role. This is often referred to as the hypothalamic-pituitary-testicular axis, or HPTA. The hypothalamus releases a hormone known as gonadotropin-releasing hormone, or GnRH. GnRH travels to the anterior portion of the pituitary gland where it causes the release of follicle-stimulation hormone, or FSH, and luteinizing hormone, or LH (see reference 3). LH travels to the Leydig cells of the testicles where it stimulates them to create and release testosterone.
Exogenous Testosterone Use
When you are on testosterone therapy, there is a large amount of circulating testosterone in the blood. This testosterone will eventually reach the brain where it causes the hypothalamus and pituitary to stop releasing GnRH and LH. This is the negative feedback loop in action. With the use of exogenous, or outside source, testosterone, the body will begin to stop producing and releasing its own testosterone. This is why the testicles may atrophy, or shrink, during the use of testosterone therapy.
Stimulating Testosterone Production
The use of the hormone hCG while on testosterone therapy may help you to continue to produce your own testosterone and reduce some testicular atrophy. Research William Llewellyn notes that prolonged use of hCG can cause over-sensitization of the Leydig cells causing them to not produce testosterone. HCG causes the pituitary to release LH, which will then travel to the testicles and cause the synthesis and release of testosterone. For testosterone restoration while on testosterone therapy, 250 International Units, or IU, of hCG is usually injected every three to four days.
References
- "Mayo Clinic"; Testosterone Therapy: Key to Male Vitality?; Mayo Clinic Staff; April 2010
- "Anabolics (10th Edition)"; William Llewellyn; 2011
- "Human Anatomy And Physiology"; Elaine Marieb, R.N., Ph.D.; 2007
