It's been a half-century since the advent of a reliable birth control option for women, and we've developed virtually nothing similar for men. But now, owing to research done at Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, an innovative new treatment holds promise as a reversible birth control option for men -– a combination of gels that get applied through the skin.
The secret is combining the male hormone testosterone with a new synthetic progestin called Nestorone, which reduces male sperm production dramatically, according to a research team led by Christine Wang. Very low sperm counts resulted for about 89% of men who used the new combination of hormones.
This is not the first time that testosterone and progestin have been used together in hopes of creating a male contraceptive. Up until now, however, these treatments had to be administered through progestin pills, implants, or injections at clinics. The transdermal gels, on the other hand, are far less invasive and can be applied by men at home.
The way it works is that progestin increases the contraceptive effectiveness of testosterone. When applied together, they turn off production of reproductive hormones controlling the production of sperm. And unlike other progestins, Nestorone has no androgenic (male hormone) activity, which can cause such side effects as acne and changes in good and bad cholesterol.
When testing the gels, the researchers found that 88-89% of men obtained a sperm concentration less than 1 million sperm per milliliter, a level the researchers describe as being "compatible with very low pregnancy rates." This compares to 23% of men who received the testosterone treatments alone.
And of those who received the treatments of both testosterone and progestin, upwards of 78% experienced a complete absence of sperm production (depending on the progestin dose).
This is obviously very encouraging, but the numbers are far from perfect — and they're still far from the effectiveness experienced by women who take birth control pills. Women who are on the pill experience pregnancy at rates of 0.3% per year. The contraceptive gels, on the other hand, are still resulting in unacceptably high sperm production for about 10% of males, which clearly poses a pregnancy risk. It's clear that more work on this particular treatment is warranted before such a product hits the market.
The study will be presented at The Endocrine Society's 94th Annual Meeting in Houston.
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