Which diagnosis is described?

Hashimoto thyroiditis is an autoimmune disorder characterized by the destruction of thyroid tissue, leading to hypothyroidism rather than hyperthyroidism. This condition typically presents with decreased levels of T3 and T4, not elevated ones, and would show reduced radioactive iodine uptake due to the impaired function of the thyroid.

Myxedema refers to severe hypothyroidism and presents with low levels of T3 and T4 hormones. The condition results from prolonged untreated hypothyroidism and would not exhibit increased radioactive iodine uptake, as the thyroid gland is underactive rather than overactive.

A simple goiter indicates an enlargement of the thyroid gland, which may or may not be associated with hormone level changes. While it can occur in cases of iodine deficiency or other thyroid dysfunctions, it does not specifically correlate with increased T3 and T4 levels or heightened radioactive iodine uptake.