A 44-year-old woman was found to have new diffuse lung uptake on a follow-up whole-body I scan 1 year after being treated with surgery and radioactive iodine for papillary thyroid cancer. However, subsequent CT thorax and thyroglobulin levels were both unremarkable. Shortly after, she presented with respiratory symptoms, exhibiting end-expiratory wheezing on auscultation. Metacholine challenge test confirmed asthma. Symptoms improved under inhaled corticosteroids and beta-2 agonists. Resolution of lung uptake was confirmed on a second I imaging 6 months later.