1. Low Testosterone Pictures Slideshow
2. Take the Low Testosterone (Low T) Quiz
3. Impotence Pictures Slideshow

Medical Author:

Charles Patrick Davis, MD, PhD

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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Medical Editor:

Melissa Conrad Stöppler, MD, Chief Medical Editor

Melissa Conrad Stöppler, MD, Chief Medical Editor

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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The causes of low-T are many and can be separated into three categories: primary, secondary, and tertiary.

Primary types of low-T or primary hypogonadism refer to the injury or failure of organs that are the main producers of testosterone, the testes atnd ovaries. Causes of primary low-T include scrotal or testicle injuries, undescended testicles, mumps, orchitis, chemotherapy or radiation therapy, chromosomal abnormalities, ovarian failure or surgical removal, and aging.

Causes of secondary low-T or secondary hypogonadism are related to the pituitary gland regulation of testosterone, while tertiary low-T or tertiary hypogonadism is related to the hypothalamus (a gland within the brain that regulates the pituitary and other glands) regulation of testosterone. Most causes of secondary and tertiary low-T are the same for the pituitary and hypothalamus; in addition, the causes may affect both at the same time. Causes of secondary and tertiary low-T include:

• Tumors associated with the pituitary or hypothalamus
• Chemotherapy of nearby tumors
• Gland malformations
• Decreased blood flow to glands for any reason
• Gland inflammation due to disease (HIV, tuberculosis, sarcoidosis)
• Taking anabolic steroids to enhance performance or muscle mass (athletes, body builders)

There are other causes that reduce testosterone that do not fit well into the above categories. Most notable is obesity, in which fat cells enhance conversion of testosterone to estrogen. Diseases such as diabetes, renal disease, COPD, high blood pressure, and lifestyles that include smoking and drug abuse also contribute to low-T.

Other less frequent causes are modified cell receptors for testosterone and unusual cell mechanisms that are rarely identified.

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