Elevated levels of prolactin in nulliparous women

Abstract

Summary.-Follicular-phase (Day 11) plasma prolactin, and plasma and urinary oestrogen levels of 70 nulliparous nuns were compared with those of 80 of their sisters, of whom 62 were parous. The nuns and their nulliparous sisters did not differ significantly in their prolactin and oestrogen levels. No differences in plasma oestrogens or urinary oestriol ratio were found between the parous and the nulliparous women. However, the mean prolactin level of the nuns and their nulliparous sisters was 3500 higher than that of the parous women in the sample taken 13 h after rising (P < 0-0005), and 24% higher (P <0.01) in the 2nd sample taken 2 h later. The elevation was independent of age, weight, and age at menarche. Age at first full-term pregnancy, at least up to the age of 30, and second or subsequent full-term pregnancies had no further effect on prolactin level. This study suggests that the effect of early first full-term pregnancy in lowering breast cancer risk may be mediated, at least in part, by permanently lowering the level of circulating prolactin.ONE OF THE MOST STRIKING breastcancer risk factors is age at first full-term pregnancy (FFTP): women whose FFTP is before the age of 20 have less than half the breast-cancer risk of nulliparous women (MacMahon et al., 1973). Two theories have been proposed to "explain" how this protective effect of early FFTP is brought about. Cairns (1975) theorized that early FFTP would effectively reduce the number of susceptible breast "stem" cells, while Cole et al. (1976) proposed that the protective effect may be due to a change in the "urinary oestriol ratio". There is no evidence available to either support or refute Cairns's hypothesis, but there is some evidence that early FFTP does increase the urinary oestriol ratio (Cole et al., 1976;Trichopoulos et al., 1980).Prolactin may also play a key role in determining risk of breast cancer (Hill et al., 1976;Malarkey et al., 1977;Pike et al., 1977;Welsch & Meites, 1978) and we were struck by the finding of Vekemans & Robyn (1 975a) in a cross-sectional study that prolactin levels decreased after age 25 in women but not in men. If this decrease with age in women is due to pregnancy, this prolactin change may be a critical part of the protective effect of early FFTP.In this paper we describe our results in comparing the plasma prolactin, and plasma and urinary oestrogen levels of nulliparous and parous women aged in California. METHODSWith the cooperation of a number of Catholic orders in California, we identified Caucasian nuns aged 20-39, who had never been pregnant and who had at least one sister aged 20-39 residing in the continental U.S. We excluded nuns who had had uterine (excluding D&C) or ovarian surgery. We also

Reproductive factors and family history of breast cancer in relation to plasma prolactin levels in premenopausal and postmenopausal women

“…[9][10][11][12][13] Parous postmenopausal women also had significantly lower prolactin levels than nulliparous women, consistent with 2 prior studies, 9,14 though the difference was not as large as among premenopausal women. We did not observe a significant gradient in prolactin concentration with increasing number of children, similar to the results of some 10,11,13 but not all 9,12,14 studies. In one of the studies with an observed gradient, the difference between nulliparous and uniparous was greater than between subsequent number of children.…”

“…9 In the other 2 studies, the change in prolactin levels with each child was relatively small (<1 ng/mL), similar to what we observed with a continuous variable, and may have been statistically significant given the large sample sizes (n 5 4,550 and 2,119). 12,14 While pregnancy appears to decrease prolactin levels, an additional benefit of earlier age at first birth has not been shown in the few prior studies of this association [11][12][13][14] or in the current study.…”

“…Other birthrelated factors, such as age at first birth, time since last birth and history of lactation, have been assessed in only a few studies, with no clear associations. [11][12][13][14][15] Few studies have examined these associations in postmenopausal women. 9,14 A prior analysis of the correlations between breast cancer risk factors and prolactin levels was conducted among 217 postmenopausal women within the Nurses' Health Study (NHS).…”

“…7,8 While the association between prolactin levels and breast cancer risk is fairly consistent, whether lifestyle or reproductive factors influence prolactin levels is not well known. A number of cross-sectional studies have observed an inverse association between parity and prolactin levels in both premenopausal [9][10][11][12][13] and postmenopausal 9,14 women, although whether prolactin levels decline further after the first pregnancy is unclear. Other birthrelated factors, such as age at first birth, time since last birth and history of lactation, have been assessed in only a few studies, with no clear associations.…”

Effects of Parity on Pregnancy Hormonal Profiles Across Ethnic Groups with a Diverse Incidence of Breast Cancer

“…These results are consistent with previous observations on long-term effects of a first pregnancy on the hormonal environment. Reductions in hormone concentrations after a first full-term pregnancy were reported in both pregnant and nonpregnant states for estrogens in serum (16,25,26,35,36) and breast fluid (37), serum adrenal androgens dehydroepiandrosterone and sulfated dehydroepiandrosterone (38), serum hCG (39)(40)(41)(42), and prolactin (13,43). Musey et al have described significant long-term decreases after a first pregnancy in basal and perphenazine-stimulated levels of prolactin (13), as well as with dehydroepiandrosterone and sulfated dehydroepiandrosterone (38).…”