SUMMARY A 66 year-old woman with a history of a euthyroid multinodular goiter underwent a head and neck computed tomography (CT) scan (total iodine load of 35 g) in order to evaluate the extent of retrosternal expansion. Less than 24 h after the iodine-based contrast media (ICM) administration, she presented with symptoms and laboratory findings typical of thyrotoxicosis. She was treated successfully with antithyroid medications. This is the shortest time reported in the literature and it is of clinical importance, as it may have an impact to the recommendations given by the attending physician. Given the fact that a large number of ICM examinations are performed in everyday practice, physicians should be aware of this possible thyroid-specific effect. Prophylactic drugs could be considered in high-risk populations, such as administration of perchlorate and a thionamide class drug to elderly patients with suppressed TSH and/or palpable goiter, started the day before and continued for two weeks after ICM administration.

Os cistos de paratireoide (PCs) são lesões raras, localizadas no pescoço e na região do mediastino anterior. A grande maioria é não funcionante, apresentando-se como lesões cervicais nodulares. PCs não funcionantes de grandes dimensões podem se manifestar com sintomas compressivos. Raramente, PCs produzem quantidades excessivas de hormônio da paratireoide (PTH), o que resulta em hiperparatiroidismo primário. Relatamos um caso de PC funcional, descrevendo sua abordagem diagnóstica e terapêutica.

Parathyroid cysts (PCs) are rare lesions, located in the neck and anterior mediastinal region. The vast majority are non-functioning, presented as nodular cervical lesions. Large, non-functioning PCs can manifest with compressive symptoms of the surrounding tissues. Rarely, PCs produce excessive amounts of parathyroid hormone (PTH), resulting in primary hyperparathyroidism. We report a case of functional PC, describing its diagnostic and therapeutic approach.