Gonadotropin levels in mothers who have had two sets of DZ twins.

Serum gonadotropin, estradiol, prolactin and alpha-1-antitrypsin levels were measured in the first four days of the menstrual cycle in 14 women who were cycling normally. FSH, and to a lesser extent LH levels, were significantly higher in a group of 8 women who had at least one set of DZ twins (6 of whom had 2 sets) than in a control group of 6 women with no DZ twins. Estradiol levels also tended to be higher in mothers of twins but there were no significant differences in prolactin or alpha-1-antitrypsin concentrations. There were no differences between the means of the two groups in age, height, weight or number of pregnancies.