Association between mutations of the follicle-stimulating-hormone receptor and repeated twinning.

Follicle-stimulating hormone (FSH) has a role in folliculogenesis and spontaneous twinning. Using the candidate gene approach, we searched for mutations in the gene encoding the FSH receptor in a woman who had given birth to two sets of dizygotic twins without fertility treatment. We identified two linked mutations (Thr307Ala and Asn680Ser) that were closely associated with this phenotype. We suggest that expression of both mutations increases the sensitivity of the receptor to FSH.