As early as the 1930’s researchers discovered that stallions had high levels of estrogen in their urine. Since then, males from many species have been found to produce estrogen and receptors for estrogen can be found throughout development and adulthood. Researchers have more recently come to discover that estrogen plays a role in the normal physiology of both reproductive and nonreproductive organs in males. In females, estrogens are mainly produced by the ovaries. In contrast, males can produce estrogens from androgens through the action of an enzyme called aromatase. This conversion process happens in the testes, fat, brain, skin and bone. Studies have shown that in males, estrogen regulates bone growth, glucose and fat metabolism, in addition to playing an important role in fertility. In fact, low circulating estrogen concentrations are a better predictor than testosterone of osteoporosis and fracture risk in elderly men. Additionally, estrogens may help protect the brain after a traumatic brain injury (TBI) or stroke and may offer protection from the development of schizophrenia. Estrogens are also associated with helping to regulate immunity, bladder function, and wound healing.
Although more studies are needed to fully understand the myriad of functions estrogens play in males, these studies may pave the way to potential new therapies for estrogen-related diseases in both men and women.
PS Cooke, MK Nanjappa, C Ko, GS Prins, RA Hess. Estrogens in Male Physiology. Physiological Reviews. Published 24 May 2017 Vol. 97 no. 3, 995-1043. DOI: 10.1152/physrev.00018.2016