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What is testosterone and its role in the body?

Updated

Testosterone is a steroid hormone essential for male development and overall health, produced mainly in the testes in men and in smaller amounts in the ovaries in women and the adrenal glands in both sexes. It is regulated by the hypothalamic-pituitary-gonadal (HPG) axis, where the hypothalamus releases gonadotropin-releasing hormone (GnRH), stimulating the pituitary gland to secrete luteinizing hormone (LH), which then acts on the Leydig cells in the testes to produce testosterone. Testosterone is crucial for the development of male reproductive tissues, secondary sexual characteristics such as muscle and bone mass, and body hair growth. It plays a critical role in spermatogenesis, the process of sperm production in the testes. As the primary anabolic hormone, testosterone promotes muscle growth and strength, influencing anabolic hormone responses like growth hormone (GH) and insulin-like growth factor 1 (IGF-1) after resistance exercise. It also helps maintain bone density and strength, reducing the risk of osteoporosis.

Additionally, testosterone levels are linked to mood and cognitive functions, with low levels leading to symptoms such as depression, fatigue, and irritability. While testosterone can improve lipid profiles and reduce fat mass, it also poses potential cardiovascular risks, such as increasing blood pressure and the risk of cardiovascular events. It is essential for maintaining libido and erectile function, influencing sexual desire and the mechanisms involved in erections. Testosterone levels naturally decline with age, leading to reduced libido, decreased muscle mass, and increased body fat, with chronic conditions like kidney disease and obesity further impacting levels. Environmental factors, such as exposure to perfluoroalkyl substances (PFASs), can also disrupt hormone levels, including testosterone. 


Further Reading:

  1. Yeap, B. B., Manning, L., Chubb, P., Handelsman, D. J., Almeida, O. P., Hankey, G. J., & Flicker, L. (2017). Progressive impairment of testicular endocrine function in ageing men: Testosterone and dihydrotestosterone decrease, and luteinizing hormone increases, in men transitioning from the 8th to 9th decades of life. 88(1), 88–95. https://doi.org/10.1111/cen.13484
  2. Zhao, J. V., & Schooling, C. M. (2020). The role of testosterone in chronic kidney disease and kidney function in men and women: a bi-directional Mendelian randomization study in the UK Biobank. BMC Medicine, 18(1). https://doi.org/10.1186/s12916-020-01594-x
  3. Kraemer, W. J., Ratamess, N. A., & Nindl, B. C. (2017). Recovery responses of testosterone, growth hormone, and IGF-1 after resistance exercise. Journal of Applied Physiology, 122(3), 549–558. https://doi.org/10.1152/japplphysiol.00599.2016
  4. Ruth, K. S., Day, F. R., Tyrrell, J., Thompson, D. J., Wood, A. R., Mahajan, A., Beaumont, R. N., Wittemans, L., Martin, S., Busch, A. S., Erzurumluoglu, A. M., Hollis, B., O’Mara, T. A., McCarthy, M. I., Langenberg, C., Easton, D. F., Wareham, N. J., Burgess, S., Murray, A., & Ong, K. K. (2020). Using human genetics to understand the disease impacts of testosterone in men and women. Nature Medicine, 26(2), 252–258. https://doi.org/10.1038/s41591-020-0751-5
  5. Cunningham, G. R., Stephens-Shields, A. J., Rosen, R. C., Wang, C., Bhasin, S., Matsumoto, A. M., Parsons, J. K., Gill, T. M., Molitch, M. E., Farrar, J. T., Cella, D., Barrett-Connor, E., Cauley, J. A., Cifelli, D., Crandall, J. P., Ensrud, K. E., Gallagher, L., Zeldow, B., Lewis, C. E., & Pahor, M. (2016). Testosterone Treatment and Sexual Function in Older Men With Low Testosterone Levels. The Journal of Clinical Endocrinology & Metabolism, 101(8), 3096–3104. https://doi.org/10.1210/jc.2016-1645
  6. Lewis, R., Johns, L., & Meeker, J. (2015). Serum Biomarkers of Exposure to Perfluoroalkyl Substances in Relation to Serum Testosterone and Measures of Thyroid Function among Adults and Adolescents from NHANES 2011–2012. International Journal of Environmental Research and Public Health, 12(6), 6098–6114. https://doi.org/10.3390/ijerph120606098
  7. Fugl-Meyer, K., Nilsson, M., Hylander, B., & Mikael Lehtihet. (2017). Sexual Function and Testosterone Level in Men With Conservatively Treated Chronic Kidney Disease. American Journal of Men’s Health, 11(4), 1069–1076. https://doi.org/10.1177/1557988317703207
  8. Moran, L. J., Brinkworth, G. D., Martin, S., Wycherley, T. P., Stuckey, B., Lutze, J., Clifton, P. M., Wittert, G. A., & Noakes, M. (2016). Long-Term Effects of a Randomised Controlled Trial Comparing High Protein or High Carbohydrate Weight Loss Diets on Testosterone, SHBG, Erectile and Urinary Function in Overweight and Obese Men. PLOS ONE, 11(9), e0161297. https://doi.org/10.1371/journal.pone.0161297