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Testosterone is an endogenous hormone responsible for the normal growth and development of the male sex organs and for maintenance of secondary sex characteristics. In a normal male, total testosterone (T) levels range from 300 to1140 ng/dL with levels below 300 ng/dL considered low Testosterone or Male hypogonadism and often results from insufficient secretion of testosterone. 1,2
Male hypogonadism is defined by at least two consecutive measurements of total T, typically in the morning, < 300 ng/dL in conjunction with signs and symptoms associated with hypogondism.
Prevalence of Hypogonadism and Associated Conditions
Testosterone levels in men decline with age, at a rate of about 1% per year beginning at about 40 years old.3 Epidemiological studies have determined that total testosterone follows an age-related decline with mean serum concentration at the age of 75 years approximately two thirds that at 25 years.4
According to reports, approximately 74% of chronic opioid users5, 50% of AIDS patients6, 52% of obese men7, 50% of diabetic men7,8 have low testosterone.
Other causes of lowered testosterone levels include: injury, infection, or loss of the testicles; chemotherapy or radiation treatment for cancer; genetic abnormalities such as Klinefelter's Syndrome (extra X chromosome); hemochromatosis (too much iron in the body); dysfunction of the pituitary gland; inflammatory diseases such as sarcoidosis (a condition that causes inflammation of the lungs); chronic illness; chronic kidney failure; liver cirrhosis; stress; and, alcoholism.
3 Feldman HA, et al. J. Clin Endocrinol Metab 2002; 87 (2):589-98
4 Myers et al. Rev Urol 2003; 5 (4) 216-226
5Daniell HW., J Pain. 2002; 3:377-384
6Dobs AS. Baillière’s Clin Endocrinol Metab. 1998; 12:379-390
7Mulligan T, et al. Int J Clin Pract. 2006;60:762-769
8Bodie J, et al. J Urol. 2003;169:2262–2264
9Jackson JA et al., AM. J. Med. Sci. 1992,304 (1) 4-8
Testosterone Replacement Therapy Market
Nearly 500,000 new cases of low testosterone are expected per year in the US as the male population ages.10 Approximately 39% of men over the age of 45 have low testosterone (hypogonadism).11 Based upon this prevalence rate and the U.S. Census Bureau's 2009 estimate that there are 48 million men between 45 and 75 years old, approximately 19 million men in the US may have low testosterone.12 Only 12% of the men with low testosterone receive testosterone replacement therapy according to a study published in Archives of Internal Medicine in 2008. Sales for male testosterone products in the U.S. were $2.0 billion in 201413 and there were approximately 6.5 million prescriptions in 2014.14
The testosterone replacement therapy market is dominated by topical products with injectables also offering a significant option. However, currently marketed non-oral products have significant compliance and advertent testosterone transfer issues.
10 Journal of Clinical Endocrinology and Metabolism, 2004
11 Mulligan et al. Int J CLin Pract 2006; 60(7) 762-769
12International Journal of Clinical Practice, 2006
13Endo Pharmaceuticals 2014 Annual Report
1 Cooper, Robert (January 21, 2010). Medline Plus. United States National Library of Medicine
2 Nieschlag E. Journal of Andrology (2006)