Twins prone to early menopause

The prevalence of early menopause, also known as premature ovarian failure, among identical and fraternal twins is triple that of women in the general population, according to analysis of twin registries in Australia and the UK.

After hearing anecdotal reports about twin pairs having a higher than average rate of premature ovarian failure, Dr. Roger G. Gosden and his associates obtained data for 428 female twin-pairs in the Australian Twin Registry and 404 pairs in the UK Twin Registry.

Roughly half of the twin pairs were identical twins, who share the same DNA, and the other half were fraternal twins, who are as close genetically as other sisters.

The rate of menopause in the twins was compared with that of women in the general population, using the 3,483 women in the European Prospective Investigation in Cancer and Nutrition database as the comparison group.

Gosden, from the Weill Medical College of Cornell University in New York and his team report in the journal Human Reproduction, published online on October 25, that rates of premature ovarian failure were similar in the two twin groups, which were significantly higher than in women entered in the general population.

The proportion of identical twins who reached menopause before 40- or 45-years old was three- to five-times greater compared with the women in the general population. The findings were similar for the fraternal twins, with these women also reaching menopause well before the women in the general population.

There was concordance for menopausal age between the identical twins, but not for the fraternal twins. Gosden’s group observed that if one identical twin experienced menopause before 40 years of age, her sister was 6.9 times as likely to also do so.

However, cncordance was not always the case for the identical twins. Among discordant pairs, the authors observed no difference in birth weights, ruling out the notion that prenatal growth may be associated with an early menopause.

The researchers examined various possible explanations for the association between early menopause and being a twin, but “no specific factors were found to account for the higher risk.” Nevertheless, they point out, even with the higher rate of premature ovarian failure among twins, the condition is still uncommon.

SOURCE: Human Reproduction, October 2006.

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