What autoimmune condition is characterized by hyperthyroidism symptoms and diffuse thyroid enlargement?

The condition characterized by hyperthyroidism symptoms and diffuse thyroid enlargement is autoimmune thyroid hyperplasia, commonly known as Graves' disease. This autoimmune disorder leads to the overproduction of thyroid hormones (hyperthyroidism) due to the presence of autoantibodies that stimulate the thyroid gland. The result is an enlarged thyroid (goiter) and symptoms associated with excess thyroid hormone, such as weight loss, heat intolerance, and increased heart rate.

In autoimmune thyroid hyperplasia, the antibodies primarily target the thyroid-stimulating hormone (TSH) receptor, mimicking the action of TSH. This continuous stimulation causes the thyroid gland to grow and produce excessive amounts of thyroid hormones. The resultant diffuse enlargement of the thyroid reflects this hyperactivity.

It is essential to differentiate this condition from others mentioned, such as pituitary neoplasm or thyroid neoplasm, which do not primarily cause diffuse enlargement or hyperthyroidism through autoimmune mechanisms. Surreptitious ingestion of T4 can lead to hyperthyroid symptoms but does not cause true thyroid enlargement in the same manner as autoimmune thyroid hyperplasia.