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Low Testosterone

The testosterone hormone is required for male reproductive development as well as impacting other physical characteristics. Low testosterone levels may be related to aging, injuries, genetic problems or other factors.

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Testosterone is a hormone produced by reproductive organs in both men (testicles) and women (ovaries), with small amounts also being produced by the adrenal glands. Men produce much higher rates of testosterone than women, and the hormone is required for male reproductive development. Testosterone is also responsible for a number of secondary “masculine” characteristics, such as a deep voice, larger muscles, facial hair, etc.

Causes of Low Testosterone

Low testosterone levels in men, also known as hypogonadism or Low T, is an endocrine disorder that typically results in a severe testosterone deficiency. Stated simply, the testicles may not produce adequate amounts of testosterone due to injury, genetic problems, chemotherapy or other conditions or environmental factors. Problems with the hypothalamus and pituitary gland, which control testosterone production, may also cause low testosterone.

Another cause of low testosterone is Klinefelter syndrome. This chromosomal condition can stunt the growth of male sexual organs before birth as well as during puberty. The syndrome affects approximately 1 in 500 to 1 in 1,000 males born each year. Men with Klinefelter syndrome may be more at risk for other diseases and disorders as well, including breast cancer or systemic lupus erythematosus (an inflammatory condition). 1

Testosterone production in men generally declines with age by about 1% per year, often beginning between 40 and 50 years old. However, medically-diagnosed low testosterone can affect men of any age.

Symptoms of Low Testosterone

Low testosterone can affect men in any of the following ways:

  • Lower sex drive (low libido)
  • Decreased sense of vitality, tiredness, less energy
  • Muscle weakness, reduced muscle mass
  • Erectile dysfunction (ED)
  • Weight gain, particularly around the waist
  • Reduced bone density (osteoporosis)
  • Depression
  • Anemia

Receiving a Hypogonadism Diagnosis

A simple blood test can check male hormone levels to detect low testosterone. The Endocrine Society considers low testosterone to be a total testosterone level of less than 300 ng/dl. 2

The line defining low and normal testosterone should be drawn to maximize benefit and minimize harm to the patient. However, reference ranges can vary widely from lab to lab, and lab reports should contain the range the lab uses. After the blood test, a follow-up visit with a doctor can usually confirm the existence of hypogonadism.

Testosterone Replacement Therapy (TRT) Options

Men who are diagnosed with low testosterone can undergo FDA-approved testosterone replacement therapy in a variety of forms, including topical gel, transdermal patch, buccal system, injection, and subcutaneous pellets.

However, there is some controversy related to TRT, especially for older men (over 65) who may have an increased risk of coronary problems after beginning the therapy, and men younger than 65 with a history of heart disease. In addition, some pharmaceutical companies have issued recalls of testosterone for various reasons.

  1. Genetics Home Reference. Klinefelter syndrome. (July 21, 2014). National Institutes of Health. Accessed July 29, 2014. 

  2. Endocrine Society. Testosterone Therapy in Adult Men with Androgen Deficiency Syndromes: An Endocrine Society Clinical Practice Guideline. (June 2010). Accessed July 22, 2014.