Hypothyroidism is a common endocrine disease in the elderly, and occurs more frequently in aged women. Because of its insidious onset (hypothyroidism-associated symptoms are very similar to those of aging process), hypothyroidism is easy to be missed in the diagnosis for the elderly people. Its most common cause is autoimmune thyroiditis. However, coexisting chronic illness and polypharmacy in the elderly make the diagnosis and subsequent management challenging. Synthetic L-thyroxine is the drug of first choice for senile hypothyroidism, starting from a low dose regimen followed by slowly increasing. Thyroid function should be closely monitored during dose adjustment, and needs to be regularly monitored even after stable dose. Indications for treatment of subclinical hypothyroidism in the elderly patients are controversial.