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.