Graves' Disease: This is the most common cause of hyperthyroidism (overactive thyroid). It occurs when the immune system produces antibodies that stimulate the thyroid gland to produce excess thyroid hormones.

Iodine Imbalance: Iodine is essential for thyroid hormone production. An iodine deficiency can lead to hypothyroidism or goiter (enlarged thyroid), while excess iodine can sometimes trigger hyperthyroidism.

Thyroid Nodules or Tumors: Growths in the thyroid gland can affect its function. Some nodules are benign, while others might produce excess thyroid hormones or, in rare cases, be cancerous.

Medications and Treatments: Certain drugs or treatments, such as radiation for cancer or overuse of thyroid hormone supplements, can impair thyroid function.

Genetic Factors: A family history of thyroid disease can increase susceptibility, especially to autoimmune thyroid conditions.

Environmental factors, stress, and infections may also contribute. Accurate diagnosis is critical for effective treatment and management of thyroid diseases.