Endocrine Abstracts

Dizygotic twinning is the result of fertilization of multiple follicles that develop during one ovulatory cycle. Significant factors contributing to natural DZ multiples are heredity, increased maternal age and higher parity. Older women are at higher risk for DZ twinning because they have a strongly increased risk of multiple follicle growth as a result of diminished ovarian feedback from the due to a smaller available cohort of follicles. FSH increases allowing all follicles present to develop and potentially ovulate. With familial twinning elevations of FSH are also found. Another hormone may be a good estimate for ovarian aging; anti mullerian hormone (AMH). Lower levels are associated with aging ovaries. AMH has been determined in the residual serum of the 16 mothers of DZ twins and 14 controls. This may reveal that the twin mothers of our study may already have shown some subtle features of limited ovarian reserve indicating protracted organ ageing. The average AMH levels were not different: 2.13±0.50 μ/l the twin mothers and 1.85±0.60 in the controls. The average calendar age was 35 years in both groups. Among the 16 familial twin mothers, 7 had elevated FSH values over 10 U/l in the early follicular phase compared to 1/14 in the control (P<0.04). Their AMH was very low compared to the 9 twin mothers with normal FSH values: 0.57±0.15 and 3.37±0.88 μ/l (P=0.016). None of the twin mothers (currently>45 years), reported early menopause (<45 years).

Our data indicates that among mothers with familial DZ twins, elevated FSH occurs often and seems to be associated with signs of limited ovarian reserve. These findings support the hypothesis that with familial DZ twinning potentially inheritance of processes that advance ovarian ageing can be responsible.