Endocrine Abstracts

Lactation is a hormonally controlled process that promotes infant growth and development and reduces the long-term maternal risk of diabetes, cardiovascular disease and breast cancer. Hormones, such as prolactin and progesterone, mediate mammary development during pregnancy and are critical for initiating copious milk secretion during postpartum days 1-4. However, the hormone concentrations and mechanisms mediating lactation onset during this period of secretory activation are ill-defined. The Larsson-Rosenquist Foundation Oxford Centre for the Endocrinology of Human Lactation (LRF OCEHL) has been established to characterize the molecular endocrine basis of lactation. We are conducting the Investigating hormones triggering the onset of sustained lactation (INSIGHT) study to establish reference intervals for the circulating hormone concentrations initiating postpartum milk secretion. This single centre study is recruiting pregnant women over a 3-year period. Blood samples are obtained at 36 weeks’ gestation, and before and after a breastfeed during postpartum days 1-4. Colostrum and breastmilk are also obtained with RNA extracted for analysis of mammary cell hormone receptor expression. This presentation will describe our analysis of serum hormone concentrations and mammary hormone receptor expression during the secretory activation window in breastfeeding participants with healthy term pregnancies.