EARLIEST PREVENTION OF ENDEMIC GOITER BY IODINE SUPPLEMENTATION DURING PREGNANCY

During pregnancy complex changes of maternal thyroid function occur an d they are influenced by the maternal iodine supply. It has been demon strated that with decreasing iodine supply maternal goiter and hypothy roxinemia as well as fetal and neonatal hypothyroidism become more pre valent. Therefore iodine supplementation during pregnancy is now stron gly recommended also in areas of moderate iodine deficiency, To monito r the success of iodine supplementation and its theoretical risk of in creasing the frequency of thyroid autoantibodies, we have investigated the thyroid volume, thyroid function, urinary iodine excretion and an tibodies to thyroid peroxidase at 10-12 weeks of gestation and postpar tum in 38 mothers receiving 300 mu g potassium iodide/day and in 70 mo thers without iodine supplementation. In all of their newborns thyroid volume was determined by ultrasound. The thyrotropin (TSH) levels and antibodies to thyroid peroxidase (TPO-ab) in the neonates were measur ed in dried blood spots on filter paper from their newborn screening. Urinary iodine excretion was increased significantly after iodine supp lementation in mothers (p < 0.001) and their newborns (< 0.05). No hyp o- or hyperthyroidism was observed in the mothers or newborns. Interes tingly, no difference of maternal thyroid volumes was observed between the two groups after pregnancy, but the volumes of the thyroid glands in newborns of mothers who received iodine were significantly (p < 0. 004) lower (0.7 +/- 0.4 ml) than in the control group (1.5 +/- 1.1 ml) . There was no change in the frequency of TPO-ab in either group after pregnancy. In four mothers transplacental passage of these antibodies was documented by positive measurement in the blood sample of the new born. This study documents that iodine supplementation during pregnanc y in an area of moderate iodine deficiency results in a lower size of neonatal thyroid volume and that this supplementation was not accompan ied by an increase in the frequency of TPO-ab.