Randomized, double blind, placebo-controlled trial of low dose iodide in endemic goiter.
Iodine (I) is essential for normal thyroid function, and the majority of subjects tolerate a wide range of dietary levels. However, a subset of individuals upon exposure to normal or elevated levels of I develop thyroid dysfunction and autoimmunity. In this double blind trial, we evaluated efficacy and tolerability of low dose I in adults with euthyroid, diffuse, endemic goiter. Sixty-two subjects were randomly assigned I (0.2 mg/day) or placebo for 12 months. After termination of therapy, both groups were followed for a further 6 months. Thyroid sonography and determinations of thyroid-related hormones, urinary I excretion per 24 h, and thyroid antibodies were carried out at baseline and at 3, 6, 9, 12, 15, and 18 months. Markedly elevated urinary I values were found during therapy in subjects receiving I (32 at baseline vs. 213 micrograms/24 h at 12 months; P = 0.0001) compared to placebo (34 and 33 micrograms/24 h, respectively; P < 0.0001 vs. I). I substantially reduced thyroid volume (29 vs. 18 mL at 12 months; -38%; P = 0.0001), and at 18 months, the therapeutic effect was sustained. In the placebo group, no significant changes were observed. High microsomal and thyroglobulin autoantibody titers were present in 3 of 31 (9.7%) subjects receiving I, and I-induced hypo- and hyperthyroidism developed in 2 and 1, respectively. Fine needle biopsy revealed marked lymphocytic infiltration in all 3 cases. After withdrawal of I, thyroid dysfunctions spontaneously remitted, and antibody titers as well as lymphocytic infiltration decreased markedly. Follow-up of these 3 subjects for an additional 2 yr showed normalization of antibody titers in 2. Thus, among subjects with endemic goiter, low dose I successfully normalized thyroid volume and body I supplementation; nevertheless, reversible I-induced thyroid dysfunctions and autoimmunity were observed in nearly 10% of the subjects.
Kahaly
G
G
Department of Endocrinology/Metabolism, Gutenberg University Hospital, Mainz, Germany.
Dienes
H P
HP
Beyer
J
J
Hommel
G
G
D000328:Adult; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D019353:Endemic Diseases; D005260:Female; D006042:Goiter / Q000188:drug therapy* / Q000453:epidemiology* / Q000473:pathology; D006801:Humans; D007454:Iodides / Q000008:administration & dosage* / Q000627:therapeutic use; D008297:Male; D010919:Placebos; D013961:Thyroid Gland / Q000473:pathology; D016896:Treatment Outcome
D007454:Iodides; D010919:Placebos