American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the characteristic finding in radioiodine uptake and scan for patients with Graves disease?

1. Decreased uptake with focal activity

2. Normal uptake with no activity

3. Markedly increased uptake with diffuse activity

4. Transiently increased uptake with localized activity

The correct answer is: Markedly increased uptake with diffuse activity

In patients with Graves' disease, the characteristic finding on a radioiodine uptake and scan is markedly increased uptake with diffuse activity. This is primarily due to the hyperfunctioning of the thyroid gland as a result of autoimmune stimulation by antibodies to the thyroid-stimulating hormone receptor. These antibodies lead to an overproduction of thyroid hormones, causing the thyroid tissue to become hyperplastic and maintain a high level of activity. The diffuse increased uptake observed on the scan indicates that the entire gland is functioning at an increased rate, which is consistent with the pathophysiology of Graves' disease. Patients often present with symptoms of hyperthyroidism, and the scan reflects the underlying overactivity of the thyroid tissue, distinguishing Graves' disease from other thyroid pathologies that may have more localized or lower levels of uptake. In contrast, other options describe different scenarios that do not align with the typical presentation of Graves' disease. For example, decreased uptake with focal activity is more consistent with conditions like thyroid nodules or cancer, and normal uptake with no activity could indicate conditions such as subacute thyroiditis or hypothyroidism. Transiently increased uptake with localized activity might suggest a different type of thyroiditis or a functional adenoma rather than the diffuse changes seen in Graves