Iodide induces thyroid autoimmunity in patients with endemic goitre: a randomised, double-blind, placebo-controlled trial.
OBJECTIVE
Iodine is essential for normal thyroid function and the majority of individuals tolerate a wide range of dietary levels. However, a subset of individuals, on exposure to iodine, develop thyroid dysfunction. In this double-blind trial, we evaluated the efficacy and tolerability of low-dose iodine compared with those of levo-thyroxine (T4) in patients with endemic goitre.


METHODS
Sixty-two patients were assigned randomly to groups to receive iodine (0.5 mg/day) or T4 (0.125 mg/day) for 6 months. Subsequently, both groups were subject to placebo for another 6 months. Thyroid sonography, determination of thyroid-related hormones and antibodies, and urinary excretion of iodine were carried out at baseline and at 1, 6 and 12 months.


RESULTS
At 6 months, markedly increased urinary values of iodine were found in patients receiving iodine (36 microg/24 h at baseline, 415 microg/24 h at 6 months) compared with those receiving T4 (47 microg/ 24 h at baseline, 165 microg/24 h at 6 months; P < 0.0001 compared with iodine group). T4 administration engendered a greater (P < 0.01) decrease in thyroid volume (from 32 ml to 17 ml, P < 0.0001) than did intake of iodine (3 3 ml to 21 ml. P < 0.005). High microsomal and thyroglobulin autoantibody titres were present in six of 31 patients (19%) receiving iodine, and iodine-induced hypo- and hyperthyroidism developed in four and two of them, respectively. Fine-needle biopsy revealed marked lymphocyte infiltration in all six. After withdrawal of iodine thyroid dysfunction remitted spontaneously and antibody titres and lymphocyte infiltration decreased markedly. Follow-up of these six patients for an additional 3 years showed normalisation of antibody titres in four of them.


CONCLUSIONS
Although nearly comparable results were obtained with both treatment regimens regarding thyroid size, partly reversible iodine-induced thyroid dysfunction and autoimmunity were observed among patients with endemic goitre.
Department of Endocrinology/Metabolism, Gutenberg-University Hospital, Mainz, Germany.
G J
GJ
Kahaly
H P
HP
Dienes
J
J
Beyer
G
G
Hommel
D000328:Adult; D004311:Double-Blind Method; D005260:Female; D006043:Goiter, Endemic / Q000150:complications* / Q000000981:diagnostic imaging / Q000188:drug therapy; D006801:Humans; D007454:Iodides / Q000009:adverse effects* / Q000627:therapeutic use / Q000652:urine; D008297:Male; D008875:Middle Aged; D013961:Thyroid Gland / Q000000981:diagnostic imaging / Q000473:pathology; D013967:Thyroiditis, Autoimmune / Q000139:chemically induced* / Q000000981:diagnostic imaging / Q000473:pathology; D013974:Thyroxine / Q000627:therapeutic use; D014463:Ultrasonography
D007454:Iodides; D013974:Thyroxine