Final answer:
Graves' disease is an autoimmune disorder causing hyperthyroidism due to thyroid-stimulating immunoglobulins that stimulate the thyroid to overproduce hormones, a reaction categorized as Type II hypersensitivity.
Step-by-step explanation:
Graves' disease is an autoimmune condition and the most common cause of hyperthyroidism, marked by the overproduction of thyroid hormones. It occurs when thyroid-stimulating immunoglobulins (TSI) act on the thyroid gland, causing it to produce excessive amounts of thyroid hormones. These TSIs mimic thyroid stimulating hormone (TSH) produced by the pituitary gland, leading to disruption of the normal feedback loop that regulates thyroid hormone production.
In a person with Graves' disease, the normal regulatory mechanism is overruled by these immunoglobulins, leading to the characteristic symptoms of hyperthyroidism, such as heat intolerance, rapid and irregular heartbeat, weight loss, and goiter. Moreover, it can cause Graves' ophthalmopathy, indicated by bulging eyes. This disease is a classic example of Type II hypersensitivity, where IgG and IgM antibodies target cellular antigens with resultant tissue damage.
It is important to differentiate between Graves' disease and other thyroid conditions like Hashimoto thyroiditis, which results in hypothyroidism due to an immune attack on the thyroid gland, leading to its destruction and a subsequent deficiency of thyroid hormones.