Study of iodine transport and thyroid hormone levels in the human placenta under different iodine nutritional status

Iodine and thyroid hormones (TH) transport in the placenta are essential for fetal growth and development, but there is little research focus on the human placenta. The research aimed to investigate iodine and TH transport mechanisms in the human placenta. The placenta was collected from sixty healthy pregnant women. Urinary iodine concentration (UIC), serum iodine concentration (SIC), placenta iodine storage (PIS) and the concentration of serum and placenta TH were examined. Five pregnant women were selected as insufficient intake (II), adequate intake (AI) and above requirements intake (ARI) groups. Localisation/expression of placental sodium/iodide symporter (NIS) and Pendrin were also studied. Results showed that PIS positively correlated with the UIC (R = 0 center dot 58, P < 0 center dot 001) and SIC (R = 0 center dot 55, P < 0 center dot 001), and PIS was higher in the ARI group than that in the AI group (P = 0 center dot 017). NIS in the ARI group was higher than that in the AI group on the maternal side of the placenta (P < 0 center dot 05). NIS in the II group was higher than that in the AI group on the fetal side (P < 0 center dot 05). In the II group, NIS on the fetal side was higher than on the maternal side (P < 0 center dot 05). Pendrin was higher in the II group than in the AI group on the maternal side (P < 0 center dot 05). Free triiodothyronine (r = 0 center dot 44, P = 0 center dot 0067) and thyroid-stimulating hormone (r = 0 center dot 75, P < 0 center dot 001) between maternal and fetal side is positively correlated. This study suggests that maternal iodine intake changes the expression of NIS and Pendrin, thereby affecting PIS. Serum TH levels were not correlated with placental TH levels.