Hashimotothyreoiditis

Hashimoto's thyroiditis, also known as Hashimotothyreoiditis, is an autoimmune thyroid disorder and the most common cause of hypothyroidism in iodine-sufficient regions. It features immune-mediated destruction of the thyroid with lymphocytic infiltration and autoantibodies, especially anti-thyroid peroxidase (anti-TPO). It predominantly affects women and typically presents in middle adulthood. Genetic and environmental factors contribute, and it may be associated with other autoimmune diseases.

Clinically it often presents as a painless diffuse goiter with symptoms of hypothyroidism such as fatigue, weight gain, cold intolerance, constipation, dry skin, and hair thinning. A transient thyrotoxic phase (hashitoxicosis) can occur early. Diagnosis is by laboratory testing showing elevated TSH and low free T4 in overt hypothyroidism, or elevated TSH with normal free T4 in subclinical disease. Anti-TPO antibodies are common; ultrasound often shows a heterogeneous, hypoechoic gland. Nodules may require evaluation.

Management is lifelong levothyroxine replacement, titrated to normalize TSH. Dosing varies with age, comorbidity, and pregnancy status. Subclinical hypothyroidism is treated if TSH is persistently high or if symptoms or pregnancy risk apply. Regular monitoring of TSH (and sometimes free T4) is recommended after starting or adjusting therapy. Take levothyroxine on an empty stomach and avoid interacting substances around dosing.

Prognosis is generally good with treatment. The condition often progresses to overt hypothyroidism requiring ongoing therapy. It may be associated with other autoimmune diseases and, rarely, risk of thyroid lymphoma in long-standing disease.