Researchers at the University of Sydney have found that a contraceptive containing the hormones testosterone and progestin might become a safe, effective and reversible form of male birth control.
The researchers found that the combination of testosterone and progestin, worked better and faster to suppress sperm production in men than testosterone alone.
"It is possible to suppress sperm output to concentrations that are comparable with reliable contraception in most, but not all men. The rate of suppression is comparable to that achieved after a vasectomy," Live Science quoted lead author Peter Y. Liu, an associate professor at the University of Sydney, Australia, as saying.
Testosterone and other male hormones act as contraceptives by creating negative feedback in a man's reproductive system, suppressing the production of sperm, according to the study.
For the study, the researchers analysed 30 male hormonal contraceptive studies that included a total of 1,756 men, aged 18 to 51.
In these studies, conducted from 1990 to 2006, the men received different preparations of testosterone, with or without various preparations of the hormone progestin.
While testosterone is the primary male sex hormone, progestin is used in combination with estrogen for female contraception and occurs naturally in females as progesterone.
After the analysis, the researchers found that the combination of testosterone and progestin was more effective at suppressing sperm production that 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," Liu said.
Liu and colleagues also found that the treatment suppressed sperm output more quickly in white males but not as completely as in non-whites. Younger men with lower testosterone levels also had faster sperm production suppression.
However, the researchers also noted that it's difficult to predict which men will respond best to this combination hormonal contraception.
"Considerable progress has been made toward finding an effective combination of these two hormones. 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," Liu said.
The study was published in the Journal of Clinical Endocrinology and Metabolism.