Perinatal exposure to excess iodine can lead to transient hypothyroidism in the newborn. In Japan, large quantities of iodine-rich seaweed such as kombu (Laminaria japonica) are consumed. However, effects of iodine from food consumed during the perinatal period are unknown. The concentration of iodine in serum, urine, and breast milk in addition to thyrotropin (TSH), free thyroxine (FT(4)), and thyroglobulin was measured in 34 infants who were positive at congenital hypothyroidism screening. Based on the concentration of iodine in the urine, 15 infants were diagnosed with hyperthyrotropinemia caused by the excess ingestion of iodine by their mothers during their pregnancy. According to serum iodine concentrations, these infants were classified into group A (over 17 microg/dL) and group B (under 17 microg/dL) of serum iodine. During their pregnancies these mothers consumed kombu, other seaweeds, and instant kombu soups containing a high level of iodine. It was calculated that the mothers of group A infants ingested approximately 2300-3200 microg of iodine, and the mothers of group B infants approximately 820-1400 microg of iodine per day during their pregnancies. Twelve of 15 infants have required levo-thyroxine (LT(4)) because hypothyroxinemia or persistent hyperthyrotropinemia was present. In addition, consumption of iodine by the postnatal child and susceptibility to the inhibitory effect of iodine may contribute in part to the persistent hyperthyrotropinemia. We propose that hyperthyrotropinemia related to excessive iodine ingestion by the mother during pregnancy in some cases may not be transient.

The frequently found mutations, C1058R and C1977S, were caused by founder effects. This result suggests that Tg mutations may provide a genetic basis for the cause of familial euthyroid goiter.

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The levels of serum osteocalcin, in addition to other parameters, were monitored in athletic (N = 9) and nonathletic (N = 10) university male students before, immediately after, and 60 min after 30 min of exercise on a running ergometer and at a constant workload of approximately 50% of their maximum capacity; there was adequate replenishment of drinking water. In both groups, the increase in serum parathyroid hormone levels observed immediately after exercise correlated well with a decrease in ionized calcium as well as the total calcium, and also with an increase in serum phosphorus, whereas the concentration of serum albumin remained stable. The response of serum osteocalcin differed between the two groups, in that (1) the concentration before exercise was significantly higher in athletic than in nonathletic students (P less than 0.001), and (2) the maximum level was evident in the former group 60 min after exercise, whereas it was present in the latter group immediately after exercise. We speculate that athletic subjects have a higher turnover of bone status compared with nonathletic subjects.