What is the most common cause of hypothyroidism?

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What is the most common cause of hypothyroidism?

Autoimmune destruction of the thyroid gland is the most common cause of primary hypothyroidism in iodine-sufficient populations. Hashimoto's thyroiditis—the classic autoimmune thyroiditis—gradually replaces functioning thyroid tissue with lymphocytic infiltration and fibrosis, reducing the gland’s ability to produce thyroid hormone. Antibodies such as anti-thyroid peroxidase are often present, and the pituitary responds by increasing TSH while free T4 falls. This pattern fits the typical demographic (often middle-aged individuals, especially women) and explains why hypothyroidism develops. By contrast, Graves disease causes hyperthyroidism due to stimulating antibodies; subacute thyroiditis usually produces a brief phase of thyrotoxicosis followed by a possible hypothyroid phase; goiter is enlargement that can accompany many conditions and is not itself the specific mechanism of hormone deficiency.

Autoimmune destruction of the thyroid gland is the most common cause of primary hypothyroidism in iodine-sufficient populations. Hashimoto's thyroiditis—the classic autoimmune thyroiditis—gradually replaces functioning thyroid tissue with lymphocytic infiltration and fibrosis, reducing the gland’s ability to produce thyroid hormone. Antibodies such as anti-thyroid peroxidase are often present, and the pituitary responds by increasing TSH while free T4 falls. This pattern fits the typical demographic (often middle-aged individuals, especially women) and explains why hypothyroidism develops. By contrast, Graves disease causes hyperthyroidism due to stimulating antibodies; subacute thyroiditis usually produces a brief phase of thyrotoxicosis followed by a possible hypothyroid phase; goiter is enlargement that can accompany many conditions and is not itself the specific mechanism of hormone deficiency.

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