"Our study validates the hypothesis that twins have a statistically significantly higher prevalence of POF than women generally. The differences were large at three to five-fold at both the 40- and 45-year threshold and were similar in both the national registers. The reason that the association between twins and POF has been largely overlooked up to now is probably because POF is still uncommon, even in twins, (3 to 5 in a hundred)," said Dr Gosden.
He said the surprising finding was that POF was just as common in non-identical twins as in identical twins.
"It may be that, contrary to the usual situation of non-identical twins being more common in women past the prime age of fertility (20s), in mothers whose biological clock is running faster than normal and whose ovarian reserve is running low, the likelihood of having twins shifts to an earlier age to their peak childbearing years. So, even though they are non-identical, one or both twins born to these mothers may be inheriting her tendency to early menopause."
With identical twins, the explanation for the excess of POF would be different according to Dr Gosden, and was, as yet, unknown and more puzzling. Studies in twins and mother-daughter pairs had shown a strong heritable component for menopausal age, although the genetic factors responsible were still largely unidentified. The current study was consistent with this finding insofar as identical twins had lesser disparities in menopausal age than non-identical twins. In several diseases such as familial breast cancer or Alzheimer's disease, forms linked with mutations in single genes occur earlier in life than do sporadic cases. So, perhaps, it would not be surprising if identical twins were more synchronised for POF
Contact: Margaret Willson
European Society for Human Reproduction and Embryology