Prolactin Secretion During Prolonged Lactational Amenorrhoea

Abstract

Basal serum prolactin levels were elevated up to 66 weeks postpartum in lactating amenorrhoeic women. The serum prolactin level in fully breast-feeding women was significantly higher than in women who were partially breast-feeding. The mean basal serum prolactin level in menstruating, lactating women was significantly higher than the mean level in women who had weaned and had normal menstrual cycles. The rise in prolactin due to suckling was seen up to 66 weeks postpartum. The marked variability and lack of reproducibility of individual suckling responses may obscure the importance of prolactin secretion in the postpartum period. Nevertheless, this study confirms that prolactin secretion is increased in women with prolonged lactational amenorrhoea.

Serum lactogens possessed normal bioactivity in patients with lactation insufficiency

“…There was substantial variation in the serum lactogen levels within both the LI patient and control groups (Table 3). This finding is consistent with a variation in serum PRL levels previously reported for lactating subjects (Martin, 1983) and is probably related to a decreasing PRL response to suckling as a function of time following delivery (Bunner et al, 1978;Gross & Eastman, 1979;Hennart et al, 1981), regardless of the maintenance of an adequate milk supply (Aono et a[., 1977). A rigorous comparison of absolute levels of BA and RIA lactogen levels in the sera is not possible since the BA and RIA assays were made with different standards.…”

“…In addition, lactation is initiated in the presence of relatively high levels of PRL resulting from early, effective and frequent suckling (Aono et al, 1977). Galactopoiesis, the ongoing production of milk, appears to depend initially on sucklingrelated PRL surges but is subsequently maintained without high levels of PRL (Tyson et al, 1978;Gross & Eastman, 1979;Weichert, 1980;Hartmann & Kent, 1988). It is facilitated by the removal of local inhibitor peptides that accumulate in the breast and decrease milk synthesis (Prentice et al, 1989).…”

“…There has been little systematic work done to investigate the multiple potential aetiologies for LI. Since PRL plays an important role in lactation and its levels in the circulation can be readily measured by radioimmunoassay (RIA), numerous studies have concentrated on the serum RIA levels of PRL in lactation and LI (Aono et af., 1977;Bigg & Yen, 1977;Delvoye et al, 1977;Bunner etaf., 1978;Tyson et al, 1978;Gross & Eastman, 1979;Howie et al, 1980;Weichert, 1980;Weitzman et al, 1980;Hennart et al, 1981;Martin, 1983). However, hormone levels measured by RIA do not always correlate with the biological activities of the hormone , and while in certain pathological cases serum PRL was found to have normal activity when measured by RIA, it had markedly decreased activity when measured by the Nb2 lymphoma cell proliferation bioassay (BA) (Nagy et a[., 1991).…”

Lactation and birth spacing in highland New Guinea

“…It is apparently inconsistent, however, with evidence from two earlier studies indicating that suckling-induced PRL surges in western women decline in amplitude during the later stages of lactation (Noel et al, 1974;Gross & Eastman, 1979). However, neither of these studies controlled for changes in suckling frequency or intensity over the course of lactation.…”

Lactation is associated with an increase in slow‐wave sleep in women

“…Prolactin plays a vital role in the initiation and maintenance of lactation (Whitworth 1988). In breastfeeding women PRL levels remain elevated throughout the first 12 months postpartum with a gradual diminution (Delvoye et al 1978;Gross and Eastman 1979). Prolactin is set at a higher level than in non-lactating women over the 24-h period, with the normal level being 20 ng mL )1 and the breastfeeding baseline level averaging 30-90 ng mL )1 .…”