Long term effects of a first pregnancy on the hormonal environment: estrogens and androgens.

An early (but not a late) first pregnancy is known to be protective for breast cancer. This effect might be mediated through a long term change in the hormonal environment caused by the early first pregnancy. To investigate the possibility of such a change we carried out a prospective longitudinal study of serum and urinary estrogens and serum androgens in four groups of women, namely early (age, 18-23 yr) first pregnancy (n = 15), early control (n = 20), late (age, 29-40 yr) first pregnancy (n = 9), and late control (n = 20). The pregnancy groups were studied before (initial visit) and 7-19 months after a first pregnancy (return visit). The control groups were similarly studied, but without an intervening pregnancy. The following were measured: serum estrone (E1), 17 beta-estradiol (E2), estriol (E3), and E1 sulfate; urinary total E1, E2, E3, and glucosiduronates of these three estrogens; and serum testosterone, dehydroepiandrosterone sulfate (DHAS), and dehydroepiandrosterone (DHA). There was no significant change between the initial and return visits in serum E1, E2, E1 sulfate, or any of the urinary estrogens in either pregnancy group or in the corresponding control groups. There was, however, a significant increase in serum E3 between initial and return visits for both pregnancy groups compared with the control values. There was no significant change in serum testosterone. There was a marked significant decrease in both serum DHAS and DHA between initial and return visits in both pregnancy groups compared with the corresponding control group values. There was also a significant increase in the serum E3 to DHA ratio in both pregnancy groups. A cross-sectional study (measuring serum DHAS and DHA only) was then carried out in a series of parous and nulliparous women. The serum DHAS and DHA levels were markedly and significantly lower in parous than in nulliparous women, as expected. There was no significant relationship between serum DHAS or DHA levels and months elapsed (up to 150) since last delivery, indicating that the changes last at least for this period of time. There was no significant relationship between serum DHAS or DHA levels and parity (one to three previous pregnancies), indicating that the changes occur only after a first pregnancy.(ABSTRACT TRUNCATED AT 400 WORDS)