There are few indications for ordering a RAIU or a thyroid scan in a primary care setting. In suspected hyperthyroidism, a sensitive thyrotropin assay should be the initial test ordered. If the thyrotropin level is low or suppressed, and the diagnosis of thyroiditis vs Graves' hyper- thyroidism is not clear, a RAIU test is appropriate. In the case of a euthyroid nodular goiter, fine-needle aspiration is the most accurate initial test to evaluate for malignancy. The primary indication for a scan in the case of a euthyroid nodular goiter is a low or suppressed thyrotropin level, because malignancy is rare in a hot nodule. If thyroid cancer or congenital hypothyroidism is encountered, referral to an endocrinologist is probably the most expedient and cost-effective way to proceed.
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