The dream of many planners of the family is a birth control pill for men, something that would somehow cut production sperm, but leave intact libido and beard. For years, researchers have focused follicle stimulating hormone (FSH) for this delicate task. This hormone ripen eggs in females and was long thought to do the same for sperm - without affecting levels of the male sex hormone testosterone. But now, a pair of papers to be published in this month's issue of Nature Genetics suggests a fatal flaw in any method of birth control that is based on the judgment of the single FSH :. Developing sperm do not need to become powerful
Martin Matzuk, an endocrinologist at Baylor College of Medicine in Houston, began investigating FSH for another reason: to investigate the role of the hormone in ovarian cancer. He and his colleagues created genetically modified mice that lack the gene for FSH. When they mated adult mice, females had no hormones to develop their eggs were infertile. But men - despite having smaller testicles and sperm count lower than normal mice - were clearly fertile and produced offspring. "It was a real surprise to people," said Matzuk. "The dogma was that FSH is needed to make sperm. That's what the textbooks say."
Matzuk results are stored in an accompanying document by a Finnish team of FSH study of mutations in humans. Juha Tapanainen University Hospital of Oulu in Oulu and colleagues at the University of Helsinki studied 15 infertile women brothers who had mutations in the gene encoding the receptor for FSH. Although men with FSH mutant gene products, support cells for sperm-producing cells in their testicles lacked the hormone receptors. Five of the men shared the symptoms of mice - small testicles and reduced sperm count -. But two of the five children had generated
FSH plays a role in making sperm stimulating the Sertoli cells that provide nutrients to growing sperm cells, said Matzuk. Without these helper cells, testicles are smaller and have fewer sperm. But Finnish researchers believe that testosterone itself can partially compensate for the lack, reversing any birth control pill designed to eliminate the FSH. "The moral is, you must come up with something to do a better job of removing the sperm count," says Bill Bremner, a reproductive endocrinologist at the University of Washington. With FSH and contraceptive in a single step for men out of the picture, researchers now need to focus on a more complicated hormonal balance between FSH, testosterone and other reproductive hormones.
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