Hormonal contraception may become a safe, effective, and reversible form of birth control for men, according to a new study accepted for publication in the Journal of Clinical Endocrinology & Metabolism (JCEM). The study revealed that the combination of testosterone and progestin suppressed sperm production faster and more completely than testosterone alone.

“It is possible to suppress sperm output to concentrations that are comparable with reliable contraception in most, but not all men,” said Associate Professor Peter Y. Liu of the University of Sydney, Australia, and lead author of the study. “The rate of suppression is comparable to that achieved after a vasectomy.”

Testosterone and other male hormones act as contraceptives by creating negative feedback in a man’s reproductive system, suppressing the production of sperm.

For this study, a team of researchers analyzed all published male hormonal contraceptive studies of at least three months treatment duration from 1990 to 2006.

In a total of 30 studies, 1,756 men between the ages of 18 and 51 were treated with different preparations of testosterone, with or without various preparations of the hormone progestin. Testosterone is the primary male sex hormone. Progestin, a synthetic progesterone, is also used in combination with estrogen for female contraception, but is ordinarily not produced by men.

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,” said Liu.

The researchers also 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.

The findings also revealed that it is 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,” said Liu. “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.”

Other researcher involved in the study include Drs. Ronald S. Swerdloff (USA), Bradley D. Anawalt (USA), Richard A. Anderson (UK), William J. Bremner (USA), Joerg Elliesen (Germany), Yi-Qun Gu (China), Wendy M. Kersemaekers (The Netherlands), Robert I. McLachlan (Australia), M. Cristina Meriggiola (Italy), Eberhard Nieschlag (Germany), Regine Sitruk-Ware (USA), Kirsten Vogelsong (Switzerland), Xing-Hai Wang (China), Frederick C.W. Wu (UK), Michael Zitzmann (Germany), David J. Handelsman (Australia), and Christina Wang (USA).

The article “Determinants of the Rate and Extent of Spermatogenic Suppression during Hormonal Male Contraception: An Integrated Analysis,” will appear in the May issue of JCEM, a publication of The Endocrine Society.

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Source: Endocrine Society