85% of hyperthyroidism cases are caused by which autoimmune condition?

Graves disease is the most common autoimmune hyperthyroid condition, accounting for approximately 85% of cases. This condition is characterized by the production of antibodies that stimulate the thyroid gland, resulting in increased synthesis and secretion of thyroid hormones. The overproduction of these hormones leads to the symptoms associated with hyperthyroidism, including weight loss, increased appetite, anxiety, and palpitations.

In Graves disease, the underlying autoimmune process involves the activation of TSH receptors by antibodies (specifically thyroid-stimulating immunoglobulins), which causes excessive hormone release. This contrasts with other conditions like Hashimoto's Thyroiditis, which is primarily associated with hypothyroidism and involves the destruction of thyroid tissue rather than hyperactivity.

Understanding the mechanism of Graves disease helps clarify its prevalence as a cause of hyperthyroidism. While other conditions such as toxic adenoma or thyroiditis can lead to hyperthyroidism, they do not have the same autoimmune basis or prevalence rate as Graves disease. Thus, identifying Graves disease as the primary cause aligns with clinical findings and the autoimmune nature of hyperthyroidism in most cases.