Thyroiditis is an inflammation of the thyroid gland and the most common cause of hypothyroidism. When patients with thyroiditis have any symptoms, they are usually the symptoms of hypothyroidism. It is also common to have an enlarged thyroid that may shrink over time. The type of thyroiditis seen most often is Hashimoto’s thyroiditis, a painless disease of the immune system that runs in families. Hashimoto’s thyroiditis affects about 5% of the adult population, increasing particularly in women as they age. Another form of thyroiditis affects women of childbearing age. Postpartum thyroiditis occurs in 5%-8% of women soon after giving birth and is usually a temporary condition.