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Growth factors make an egg grow up

Reproductive biologists have closed a gap in their understanding of how the female reproductive system works, an advance that could improve in vitro fertilization procedures.

In the middle of a female mammal's reproductive cycle, a surge of luteinizing hormone (LH) floods an ovarian follicle, triggering changes that lead to the maturation and release of an egg. The mystery has been that the immature egg and its surrounding cells don't respond directly to the hormone. These cells don't sport the cell-surface protein that binds LH.

Other cells in an ovarian follicle can respond to LH, however. And now, a research team headed by Marco Conti of Stanford University School of Medicine reports that those cells, when triggered by LH, briefly produce a set of growth factors that directly spurs the maturation of an egg.

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