The Man Pill
Updated : May 5, 2009
A male contraceptive jab has proved highly effective in a large study of more than 1,000 men.
Just over one in 100 men conceived a child over a period of two years, which is considered a very good result.
No contraceptive is 100pc effective and each year between 1pc and 2pc of women on the Pill get pregnant.
The testosterone injection was tested on a group of healthy fertile Chinese men aged 20 to 45. Each had fathered at least one child in the previous two years.
Female partners were aged between 18 and 38 and had no reproductive problems.
Dr Yi-Qun Gu, from the National Research for Family Planning in Beijing, said: "For couples who can not, or prefer not to use only female-oriented contraception, options have been limited to vasectomy, condom and withdrawal.
"Our study shows a male hormonal contraceptive regimen may be a potential, novel and workable alternative."
The men were given monthly 500 milligram injections of testosterone undecanoate (TU) in tea seed oil over a period of two and a half years.
No serious side effects were reported and the men's fertility returned to normal in all but two participants after the treatment was stopped.
Testosterone injections lead to a reduction in levels of two regulatory brain chemicals, follicle-stimulating hormone (FSH) and luteinising hormone (LH).
This in turn disrupts sperm production, but the effect is reversible. Sperm counts return to normal four to six months after the injections are halted.
Results from the trial, the largest effectiveness study of a testosterone-based male contraceptive ever undertaken, will appear in the June issue of the Journal of Clinical Endocrinology and Metabolism.
Dr Gu said: "Despite the present encouraging results, the long-term safety of this hormonal male contraceptive regimen requires more extensive testing with a focus on cardiovascular, prostate and behavioural safety."
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