The reversibility of thyroid dysfunction in children with
endemic cretinism treated with supplemental
iodine is unknown. To study this question we conducted a five-month follow-up of 51 patients with
cretinism (age 14 and below), who were randomly assigned to treatment (0.5 ml of intramuscular
iodized oil) and control groups. The geometric mean initial serum level of
thyrotropin (223 microU per milliliter; SD, 97 to 513) and the mean (+/- SD) initial serum level of
thyroxine (1.0 +/- 1.2 micrograms per deciliter) indicated that all patients had severe
hypothyroidism. Within one month after receiving the
iodized oil, 13 of 14 of the younger patients (less than 4 years) and 1 of 9 of the older patients (4 to 14 years; P less than 0.001) had
thyrotropin values below 20 microU per milliliter. Five months
after treatment, the levels of
thyrotropin had decreased and those of
thyroxine had increased in all children, but greater changes occurred in the 13 younger patients than in the 14 older patients. The mean levels of
thyrotropin were 2 microU per milliliter (SD, 0.6 to 6) vs. 38 microU per milliliter (SD, 11 to 132; P less than 0.001), and the mean (+/- SD) levels of
thyroxine were 13.1 +/- 2.8 vs. 8.1 +/- 4.6 micrograms per deciliter (P less than 0.001). In the untreated group, 3 of the 9 younger patients and none of the 15 older patients recovered normal thyroid function within five months. We conclude that
iodine supplementation restored a biochemically euthyroid state in all younger children with
cretinism but only some of the older children. In addition, some younger patients became euthyroid without
iodine supplementation.