Failure of Estrogen-Induced Discharge of Luteinizing Hormone in Lactating Women

Abstract

Pituitary-ovarian relationships were studied in seven lactating women by measuring the basal plasma concentrations of pituitary and ovarian hormones and their responses to an estrogen provocation test at 7, 30, and 100 days after delivery. The results were compared to a similar group of seven women who did not breast feed. The first ovulation occurred in five of the nonlactating women beteen 43-87 days after delivery, as judged by the urinary excretion of total estrogen and pregnanediol. In all lactating women, ovarian cyclicity was suppressed for at least 150 days after delivery or until weaning. The basal concentration of PRL in lactating women was significantly higher than in the nonlactating women at all three times measured. At 30 and 100 days, the concentration of estradiol was significantly lower in the lactating women, although the basal concentrations of FSH were similar in the two groups. After an injection of 1 mg estradiol benzoate, the concentrations of FSH and LH in plasma were suppressed to a greater extent in lactating than in nonlactating women. In addition, fewer of the lactating group (one of seven and none of seven at 30 and 100 days, respectively) than the nonlactating group (two of seven and five of seven) subsequently showed a rise in the concentration of LH 58--96 h after the estrogen injection (positive feedback). These results suggest that during lactation the hypothalamic-pituitary system is more sensitive to the negative feedback and relatively insensitive to the positive feedback of estrogen.

Reproductive factors and pancreatic cancer risk: a Norwegian cohort study

“…A positive association with parity has been suggested as due to higher oestrogen levels, during pregnancy (Ji et al, 1996), and if such effects fade over time, they could produce an age interaction as seen in our study. As levels drop substantially during breastfeeding (Baird et al, 1979), a general risk-enhancing oestrogenic effect may also explain the inverse association with breastfeeding, in addition to the positive associations with abortions and age at menopause. Almost all women in our cohort were born too early to have used oral contraceptives or hormone replacement therapy, although these apparently do not affect risk (Teras et al, 2005).…”

Lactation and Risk of Endometrial Cancer in Japan: A Case-Control Study

“…Exposure of the endometrium to estrogen in the absence of progesterone is thought to increase the risk of endometrial cancer (Key and Pike 1988-see comment for citation). In lactating women, the ovarian cycle is suppressed and blood estrogen levels are reduced (Baird et al 1979). In the case of oral contraceptives, progesterone continually opposes estrogen, minimizing the duration of time the endometrium is exposed to unopposed estrogen.…”

Inhibition of ovarian function in subordinate female marmoset monkeys (Callithrix jacchus jacchus)

“…Elevated prolactin levels (hyperprolactinaemia) have also been linked with the inhibition of reproductive function (high-prolactinamenorrhoea) in women (Besser, Parke, Edwards, Forsyth & McNeilly, 1972; Tyson, Friesen & Anderson, 1972; Van Look, McNeilly, Hunter & Baird, 1977; Baird, McNeilly, Sawers & Sharpe, 1979) and in captive subordinate female talapoin monkeys, Miopithecus talapoin (Bowman, Dilley & Keverne, 1978;Keverne, 1979). In both cases, high prolactin concentrations were clearly associated with the inhibition of the ovulatory surge of pituitary LH in response to oestrogen.…”