Iodine supplementation: A comparison of oral and intramuscular methods in the improvement of thyroid function and prophylaxis of goitre

The aim of this study was to determine which method of iodine supplementation, oral or intramuscular, is most effective at reducing goitre and improving thyroid function over a 3-month period. Subjects were randomly allocated at baseline by age and sex into 3 groups: a group given a placebo capsule; a group given an oral supplement of Lipiodol (480 mg iodine); and a group given an intramuscular injection of Lipiodol. The field study was in Maskat, 1,700 meters above sea level and 250 kilometers North-West of Dar Es Salaam, Tanzania. It is only accessible on foot being 9 hours walk from the nearest village, A total of 270 school children, aged 6 - 17 years were recruited into the study at baseline and 203 subjects were available for the follow-up examination - a response rate of 75%. Personal details, anthropometric measurements and clinical data were collected at baseline. A 2 ml blood sample was taken and goitre grades recorded pre-supplementation and at the end of supplementation 3 months later. Thyroid hormone status was examined using RIA diagnostic kits (T3, T4) and a hsTSH 1-step immunoradiometric coated tube assay. TSH concentration increased significantly (p = 0.007) in the control group, Oral supplementation resulted in a decrease in goitre size and although T3 increased significantly (p = 0.024) there was no significant change in either T4 or TSH concentrations. Intramuscular supplementation improved thyroid function, indicated by a significant (p = 0.015) decrease in mean serum TSH concentration. Goitre sizes, however, increased significantly (p = 0.01) in this group. Oral iodine supplementation appears to provide a more rapid beneficial effect on goitre in the short term than intramuscular injection.