Eur Thyroid J. 2025 Nov 20:ETJ-25-0260. doi: 10.1530/ETJ-25-0260. Online ahead of print. ABSTRACT Autoimmune hypothyroidism occurs rarely before three years of age. Two siblings were diagnosed with autoimmune hypothyroidism at age five and 16 months, presenting with classic symptoms of hypothyroidism, abnormal thyroid function tests (TSH 200 and 660 mU/L;…

