Will thyroid hormones or antithyroid medications interfere with a tc99m pertechnetate thyroid scan?

Not usually. Technetium is usually trapped by thyroid gland and used to determine in young children and infants the configuration of thyroid gland, hypoplasia, absence, or increased size or hyperplasia, or abnormal location. Radioactive iodine is used in older patients for determine function of thyroid gland, increased function or hyperthyroiidism or decreased function, hypothyroidism.
Yes and No. Thyroid hormone therapy and recent administration of iodide, iodinated contrast agents, or other iodine-containing drugs will lower the thyroidal accumulation of tc99m pertechnetate. Antithyroid-drug therapy (propylthiouracil or methimazole) do not interfere with the trapping of tc99m pertechnetate.
No. Tc99 uses a different "uptake" mechanism to image the thyroid.