What is the most common cause of hypothyroidism in iodine-sufficient areas of the world?

The most common cause of hypothyroidism in iodine-sufficient areas is Hashimoto's Thyroiditis. This autoimmune condition occurs when the immune system mistakenly attacks the thyroid gland, leading to inflammation and impaired thyroid function. Over time, this can result in an underactive thyroid, causing hypothyroidism.

In iodine-sufficient regions, where a lack of iodine is not a contributing factor to thyroid dysfunction, Hashimoto's Thyroiditis becomes the predominant reason for the development of hypothyroidism. The condition is characterized by the presence of specific antibodies that target thyroid tissue, and it often presents with a painless enlargement of the thyroid gland, known as a goiter.

Other conditions listed, such as Graves' disease, subacute thyroiditis, and thyroid cancer, may contribute to thyroid dysfunction or affect thyroid hormone levels, but they are not as prevalent as Hashimoto's in terms of causing hypothyroidism in populations with adequate iodine intake. Graves' disease typically results in hyperthyroidism rather than hypothyroidism, while subacute thyroiditis usually has a more transient effect on thyroid hormone levels. Thyroid cancer might lead to hypothyroidism post-treatment (e.g., thyroidectomy), but it is less common as a direct cause of hypothyroidism. Thus