Iodine supplementation with oral or intramuscular iodized oil. A two-year follow-up of a comparative trial.

A controlled trial of iodine supplementation comparing oral with intramuscular iodized oil has been carried out in an iodine deficient area of Zaire. Two years after the administration of 2 ml of oral iodized oil to the population of four villages the overall goitre prevalence had fallen from 64 to 54%. In a further two villages given 2 ml of intramuscular oil the prevalence fell from 65 to 50%. The effectiveness of supplementation was also assessed by measuring changes in thyroid function in women of reproductive age. Among women in the villages given oral iodized oil, the geometric mean thyroxine concentration, measured in dried bloodspots, rose from 27.2 to 52.6 nmol/L at the two-year follow-up. This was similar to the response of the intramuscularly treated villages in which thyroxine levels rose from 32.1 to 65.4 nmol/L. There was no change in goitre prevalence or thyroid function in two control villages. Oral iodized oil is a cheaper and simpler alternative to the injected form providing effective iodine prophylaxis for up to two years after a single dose.