Graves disease leads to which alteration in T3 and T4 levels?

Graves' disease is an autoimmune disorder that results in the overproduction of thyroid hormones, specifically T3 (triiodothyronine) and T4 (thyroxine). In this condition, the immune system mistakenly attacks the thyroid gland, leading to its hyperactivity. As a result, both T3 and T4 levels are elevated due to the increased synthesis and release from the thyroid gland.

Because there is an excess of thyroid hormones in the bloodstream, the hypothalamus and pituitary gland sense this high hormone level and respond by reducing the secretion of Thyroid Stimulating Hormone (TSH). TSH is responsible for stimulating the thyroid to produce more hormones. So in the context of Graves' disease, elevated levels of T3 and T4 are accompanied by low levels of TSH due to the feedback inhibition mechanism.

This physiological response underscores why this condition is characterized by high T3 and T4 levels, demonstrating the classic hormonal imbalance associated with hyperthyroid states like Graves' disease.