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Scientists say they’re on the verge of having a safe birth-control shot for men.

According to a study by the Journal of Clinical Endocrinology & Metabolism, researchers gave men a shot of testosterone and other hormones, so their bodies stopped producing testosterone on their own.

Men in the study received shots every eight weeks. The injections consisted of 1,000 milligrams of a synthetic form of testosterone and 200 milligrams of norethisterone enanthate, which is essentially a derivative of the female hormones progesterone and estrogen referred to as “progestin” in the synthetic form.

Dr. Seth Cohen, a urologist at NYU Medical Center, told CNN that when a man is given a shot of testosterone, the brain assumes the body is getting enough of the hormone and shuts down its production. Specifically, it shuts down the production of the testicle’s production of sperm.

Researchers say the study was 96 percent effective.

However, side effects from the shot, like depression, caused the study to be cut short.

Researchers say they’re on the right track – they just have to work on calculating the right dose of hormones.