False hyperthyroidism caused by interference in immunoassays.

Objectives: Immunoassays used to assess thyroid function are vulnerable to different types of interference that may affect clinical decision-making.

Case Presentation: We report the case of a 37-year-old woman who developed iatrogenic hypothyroidism after having received radioiode therapy who visited our hospital for her annual checkup. The patient was asymptomatic, without signs suggestive of thyroid disease.