Supplementary iodine fails to reverse hypothyroidism in adolescents and adults with endemic cretinism.

The efficacy of supplemental iodine in correcting hypothyroidism in adults and older children with endemic myxedematous cretinism is not known. To investigate this issue we administered im iodized oil (1.5 mL) to 28 hypothyroid endemic cretins (TSH, greater than 5 mIU/L) from western China, aged 14-52 yr (mean = 29 SD = 11 yr). Clinical examination, intelligence testing (Hiskey Nebraska Test of Learning Aptitude and the Griffiths Mental Development Scales), and thyroid function tests were performed before and 6 months after iodine supplementation. We found that signs of thyroid hormone deficiency, dwarfism, and delayed sexual maturity persisted after iodine supplementation. Further, mental disability and other clinical features of neurological damage were not altered by treatment. The mean serum concentration of total T4 before treatment was 75 nmol/L (SD = 40) and fell after iodized oil administration to 56 nmol/L (SD = 29; P less than 0.001). Mean serum levels of TSH before and after iodine showed a paradoxical fall [85 mIU/L (SD = 102) and 46 mIU/L (SD = 46), respectively]. Serum TSH levels decreased into the normal range (less than 5 mIU/L) in only 1 of 28 patients (4%). We conclude that iodine supplementation does not reverse thyroid hormone deficiency or its sequelae in adolescents and adults with endemic myxedematous cretinism. Iodized oil in this age group of patients with endemic cretinism does not appear to be beneficial and should be used with caution.

Effect of iodination of a village water-supply on goitre size and thyroid function.

An iodinator was fitted to the existing gravity-fed water-supply of a remote village in Sarawak, Malaysia, where goitre was endemic. Within nine months, the prevalence of goitre had been reduced from 61% to 30%, with 79% of goitres showing visible reduction in size. All subjects were clinically euthyroid before and nine months after the start of iodination, although pre-treatment serum thyroid-stimulating hormone (TSH) concentrations varied from normal up to 24 mU/l. Before treatment basal serum triiodothyronine (T3) and thyroxine (T4) concentrations were typical of endemic goitre with a low mean serum T4 (80 +/- 30 [SD] nmol/l) and a slightly raised mean serum T3 (2.3 +/- 0.7 nmol/l). After iodination, circulating TSH concentration was generally undetectable (less than 0.1 mU/l), mean T3 concentration was unchanged, but the mean T4 rose significantly to 109 +/- 41 nmol/l (p less than 0.01). Urinary iodine concentrations fluctuated; this largely reflected intermittent blockage of the iodinator, but concentrations became consistent with a return to the iodine-replete state. There was no evidence of the Jod Basedow effect in the group studied. Iodinated water was more convenient to distribute than iodised salt and is less likely to cause Jod Basedow phenomenon than are injections of iodised oil. Moreover, iodination of water is effective in killing most microorganisms and this additional benefit could contribute significantly to village health.