Hormonal contraception may soon become a safe, effective, and reversible form of birth control for men, according to a new meta-study in the Journal of Clinical Endocrinology & Metabolism. Surprisingly, the male hormone testosterone will likely play an important role in any future contraceptive. Testosterone and other male hormones act as contraceptives by creating negative feedback in a man's reproductive system, suppressing the production of sperm.
Lead author of the study, Associate Professor Peter Y. Liu, of the University of Sydney, said the most likely formulation for a male pill would combine testosterone and progestin (a female hormone), which together are more effective at suppressing sperm production than testosterone alone. Liu added that such hormonal combinations could suppress sperm output to concentrations comparable to that achieved after a vasectomy.
Liu's review analyzed all published male hormonal contraceptive studies carried out between 1990 and 2006. The analysis revealed that the combination of testosterone and progestin was more effective at suppressing sperm production than testosterone alone. "Progestin co-administered with testosterone increased both the rate and extent of suppression. It also may make long-term hormonal contraception safer by reducing the dose of testosterone needed for maintenance contraception," explained Liu.
Interestingly, the researchers found that Caucasian men suppressed sperm output faster, but not as completely, as non-Caucasians. Also, younger men with lower natural testosterone levels had faster suppression, but the differences were relatively small.
Liu also noted that it was difficult to predict which men will respond best to the treatment, suppressing sperm output to levels consistent with reliable male contraception. "Considerable progress has been made toward finding an effective combination of these two hormones," he said. "However, the current analysis didn't take into account the different types of progestins, so more research will need to be done to find the optimum therapy."
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Source: Endocrine Society