Consequences of the chronic cutaneous application of iodinated antiseptics on the thyroid function in the guinea-pig

The effect of the chronic cutaneous application of iodine-containing substances on the thyroid function was studied in the guinea-pig. Six iodinated products were daily applied at the rate of 2 g/kg/day for 90 days. We find a quasi-abolition in the thyroid 131I-uptake (reflecting the transcutaneous absorption of free iodine) and an important transient thyroidal hyperproduction during the first month. Then, this primary hyperthyroidism induces a strong pituitary negative feed-back so that the levels of the circulating hormones T3 and T4 are normalized at the end of the experiment; a new hormonal balance is reached with a TSH level reduced by half compared to its normal value.