Postinfectious hypothyroidism

This code describes a condition where the thyroid gland is underactive (hypothyroidism) as a direct consequence of a prior infection. The infection, which could be viral or bacterial, triggers an autoimmune response or directly damages the thyroid tissue, leading to insufficient thyroid hormone production.

Use this code when documentation clearly links the onset of hypothyroidism to a preceding infectious process. This typically involves a history of an infection (e.g., subacute thyroiditis, viral illness) followed by symptoms and lab findings consistent with hypothyroidism. Physician notes explicitly stating "postinfectious hypothyroidism" or similar causal language are essential.

• Ensure the medical record explicitly states the infectious etiology of the hypothyroidism.
• Do not use for congenital, drug-induced, or other specified forms of hypothyroidism.
• Code the underlying infection if it is still active and relevant to the current encounter.