Effect of obesity and hypothyroidism on hepcidin concentration in pregnancy - a pilot study using maternal and umbilical cord blood at delivery day

Hepcidin is a primary regulator of iron metabolism in the human body. By promoting ferroportin degradation, hepcidin reduces intestinal iron absorption and its release from intracellular stores. In the course of pregnancy, gradually declining hepcidin concentrations encourage placental iron transfer, thereby providing the appropriate amount of iron for fetal development. Hence, we aimed to investigate changes in maternal and cord blood hepcidin and iron metabolism parameters in normal-weight (n=17) and obese (n=17) gestating women, as well as gravid women with a history of hypothyroidism following the restoration of euthyroidism (n=17). All blood samples were taken on the day of delivery, and ELISA kits were used for measurements. A significant increase in maternal hepcidin concentration was observed in obese pregnant women, compared to normal-weight controls (29.53±4.20 ng/mL vs. 25.69±5.70 ng/mL; P<0.05). However, only a slight, insignificant tendency for lower hepcidin was noted in the hypothyroid group, compared to the healthy controls (23.10±6.00 ng/mL vs. 25.69±5.70 ng/mL; P=NS). Moreover, decreased maternal free triiodothyronine, triiodothyronine, free thyroxine, and ferritin levels were revealed in the hypothyroid group, compared to the normal-weight individuals (P<0.05). Furthermore, positive correlations between maternal hepcidin and the majority of maternal thyroid hormones were found, with a most potent relation to FT3 (r=0.40; P<0.01). Interestingly, no alterations of thyroid hormones and iron metabolism parameters were noticed in cord blood in any of the subgroups. In summary, pre-pregnancy obesity is associated with elevated maternal hepcidin, albeit no signs of lowered cord blood iron status were shown. Medical history of hypothyroidism following the restoration of euthyroidism does not substantially influence maternal nor cord blood hepcidin concentration, as well as fetal iron homeostasis, even though free thyroid hormone levels correlate with maternal hepcidin.