In patients with hyperthyroidism due to Graves' disease, which would be an expected laboratory finding?

• A. Decreased thyroxine levels
• B. Elevated serum TSH
• C. Increased serum T3 levels
• D. Low serum T4 levels

Answer: (C)

In patients with hyperthyroidism due to Graves' disease, increased serum levels of T3 (triiodothyronine) would indeed be an expected laboratory finding. Graves' disease is an autoimmune condition characterized by the overproduction of thyroid hormones, which includes both T3 and T4 (thyroxine).

Hyperthyroidism leads to an increased synthesis and release of these hormones into the bloodstream, often resulting in elevated levels of both T3 and T4. While T4 levels are generally also elevated, T3 often shows a more pronounced increase, especially in cases of hyperthyroidism. This is due to the fact that T3 is the more active thyroid hormone and can be converted from T4 in peripheral tissues; thus, many patients with Graves' disease exhibit particularly high T3 levels.

The other options, such as decreased thyroxine levels, elevated serum TSH, and low serum T4 levels, are inconsistent with the pathophysiology of hyperthyroidism. In this condition, TSH (thyroid-stimulating hormone) levels would generally be suppressed due to the negative feedback effect of the elevated thyroid hormones T3 and T4 on the anterior pituitary. Additionally, both T3 and T4 levels would