Age at menarche and estrogen concentrations of adult women.

It has recently been reported that women with a recorded early menarche had approximately two-fold greater follicular phase serum E2 (estradiol) levels than women with menarche at age 13 or later. We have evaluated E1 (estrone) and E2 concentrations in the blood, and estrogen concentrations in the urine, in two groups of premenopausal women (mean ages 33 and 38 years) for categories of age at menarche. Study subjects were 106 Caucasian women in the United States (assessed for E1, E2, and urinary estrogens) and 39 women from Shanghai, China (assessed for E2). US subjects were classified according to whether their recalled menarche occurred before age 12, at age 12, or at age 13 or older. The mean age at recalled menarche of the Shanghai subjects was considerably older, and their ages at menarche were classified as less than age 15, age 15, and age 16 or older. We found little evidence in these premenopausal women in their thirties of an effect of age at menarche on estrogen levels. A large-scale study of women in the age range 20-40 years is necessary to investigate this important issue more thoroughly.