USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

Which condition is associated with markedly elevated serum T4/FT4 levels, increased 123I uptake, and decreased serum TSH levels?

1. Follicular adenoma

2. Riedel thyroiditis

3. Graves hyperthyroidism

4. Thyroid storm

The correct answer is: Graves hyperthyroidism

The condition characterized by markedly elevated serum T4 (thyroxine) and free T4 (FT4) levels, increased uptake of radioactive iodine (123I), and decreased serum TSH (thyroid-stimulating hormone) is Graves hyperthyroidism. In this disorder, the overproduction of thyroid hormones is primarily caused by an autoimmune response where antibodies stimulate the thyroid gland, leading to hyperplasia and excessive hormone production. The elevated T4 levels indicate hyperthyroidism, which is classified by the suppression of TSH due to negative feedback. In a normal physiological response, increased levels of thyroid hormones suppress the production of TSH from the pituitary gland. The increased radioactive iodine uptake indicates that the thyroid gland is hyperactive and properly synthesizing and absorbing iodine to produce more thyroid hormones. In contrast, conditions like follicular adenoma would typically result in increased T4 levels, but the uptake of iodine may not be as pronounced and TSH levels might not be suppressed to the same degree due to less stimulation from surrounding tissues. Riedel thyroiditis is a form of chronic inflammation that can lead to hypothyroidism rather than hyperthyroidism, thus would not present with elevated T4 or FT4. Thyroid storm is a state of acute