SERUM IODINE IN HYPERTHYROIDISM, WITH PARTICULAR REFERENCE TO THE EFFECTS OF SUBTOTAL THYROIDECTOMY 1

Abstract

The range of values of the serum precipitable I in untreated hyperthyroidism is defined. 95% of the values fell above 8 y %. If the 2 cases who were probably in spontaneous remission are excluded, 98% of the values fell above 8y%. The serum precipitable I sometimes, but not always, declined with I medication in hyperthyroidism, but only attained normal levels in a certain number of cases. Even when given for long periods it continued to exert a depressing effect on the serum precipitable I. Subtotal thyroidectomy was followed within 3 hrs. by a slight rise in serum precipitable I, not exceeding a few y %. Serum precipitable I then fell steadily, so that within 3 weeks all supranormal values had disappeared. Later elevations were rare. Subnormal values of the serum I might develop within 2 wks. following subtotal thyroidectomy. Although this depression was sometimes transient, these low values in some persisted indefinitely. Subnormal values are usually associated with some clinical evidence of mild thyroid deficiency, but the basal metabolism was often within normal limits and the serum cholesterol only slightly elevated. It is probable that low concns. of precipitable I indicate a mild form of partial hypothyroidism. Low serum I values are common enough mos. after subtotal thyroidectomy to indicate that chronic partial hypothyroidism is a not uncommon sequel of subtotal thyroidectomy.