Final answer:
The use of povidone-iodine can lead to a false increase in serum thyroid-stimulating hormone (TSH) levels due to the absorption of iodine and its effect on thyroid hormone synthesis.
Step-by-step explanation:
The use of povidone-iodine for site preparation prior to a medical procedure can result in a false increase in the serum thyroid-stimulating hormone (TSH) levels. This is because the antiseptic contains iodine, which can be absorbed into the bloodstream through the skin. The concentration of iodide ions 'trapped' in the thyroid follicular cells is many times higher than the concentration in the bloodstream. This excess iodine can lead to the Wolff-Chaikoff effect, temporarily inhibiting the synthesis of thyroid hormones and thus potentially causing a compensatory rise in TSH levels, which could be misinterpreted as a thyroid dysfunction. As a result, patients who have had recent exposure to iodine, such as through povidone-iodine, should inform their healthcare provider before having a thyroid function test.