A 60-year-old man who was recently diagnosed with lung adenocarcinoma underwent 18F-FDG positron emission tomography/computed tomography (FDG PET/CT) scan for staging. The FDG PET/CT scan showed incidental hypermetabolic uptake in the pituitary gland and focal hypermetabolic activity in the left thyroid lobe. Histopathologic evaluation revealed these to be a non-functioning pituitary adenoma and papillary thyroid cancer, respectively. Incidental hypermetabolic uptake in the pituitary and thyroid glands on FDG PET/CT scan are uncommon. It is important to determine their etiologies as this may lead in some cases to incorrect staging of the primary cancer and, therefore, inappropriate clinical management. In this case report we will discuss the clinical presentation and the imaging findings of this patient and review the related literature.