In 26 euthyroid persons without goiter the influence of various concentrations of iodide in blood on the iodine metabolism of the thyroid was investigated. This iodide level in blood was maintained for 7 days.
- 1. At a normal iodide level in blood of about 0.8 μg/100 ml the average iodine uptake of the thyroid was 13.3 μg/h.
- 2. Increasing iodide concentration in blood caused depressed uptake of 131I from a tracer dose as well as decreased T/S ratio. With the exception of 3 cases there was no uptake above 20 μg/100 ml.
- 3. The absolute iodine uptake of the thyroid depending on the concentration of iodide in blood was stimulated by moderate increases, but inhibited respectively blocked by higher ones. At a middle iodide level of 6.1, 15.1, 34.4 and 86.4 μg/100 ml of the absolute iodine uptake amounts to 82.0, 32.7, 2.0 resp. 2.1 μg/h.
- 4. The hormonal phase of the thyroidal iodine metabolism remained in most cases unchanged by the one week's iodide medication. In two cases only an activated iodine metabolism was suggested. The hormonal iodine concentration in blood never showed a thyrogenic increment.