Endocrine Abstracts

Gestational weight gain has been linked to obesity in women of childbearing age. Mothers who breastfeed present less postpartum weight retention. The underlying pathophysiological mechanisms are unknown. This study aimed at investigating the impact of breastfeeding on maternal appetite-regulating hormones.

The clinical trial recruited 29 women divided in three age- and BMI-matched groups. The first group included 10 fully breastfeeding mothers of 3 to 6 month old babies (lactating group), the second included 9 non-breastfeeding mothers of 3 to 6 month old babies (nonlactating group) and the third included 10 healthy women (control group). Participants were studied at 5 time-points during 1.5 h. The mothers of the lactating group breastfed their babies during the study period, while participants of the nonlactating group either bottlefed their babies or did not. Primary outcome parameters were ghrelin and PYY. Secondary outcome parameters were leptin, adiponectin, prolactin, PTH, osteocalcin and lipid values.

We found that lactating mothers had significantly increased circulating concentrations of the anorectic hormone PYY as compared to the two other groups (P=0.008 when compared to non-lactating mothers and P=0.02 when compared to the control group). We found no significant differences in ghrelin, leptin and adiponectin values. Prolactin levels at baseline were over 4-fold higher in lactating mothers (P<0.001) and further augmented during breastfeeding (P<0.001). In addition, lactating women presented a lower waist circumference, reduced triglyceride levels, lower total cholesterol/HDL ratio as well as significantly increased osteocalcin levels when compared to the two other groups.

In summary, breastfeeding mothers present significantly elevated circulating PYY concentrations, increased bone turnover and a better lipid profile. Differences in appetite regulation and the increase in the anorectic PYY might count among the factors underlying the higher rate of postpartum weight reduction in women who breastfeed.