FDG Uptake in Brown Adipose Tissue Activated by a β3-Adrenergic Receptor Agonist Prescribed for Overactive Bladder

Brown adipose tissue (BAT), which produces energy and is known to play a role as a hibernating gland, is sometimes visualized on F-FDG PET in children or in slender young adults in a cold environment. Because BAT is activated by catecholamines, FDG uptake in BAT is also observed in patients with pheochromocytoma or paraganglioma. We present the case of an elderly woman with remarkable FDG uptake in BAT. Activation of BAT by a β3-adrenergic receptor agonist (mirabegron) prescribed for overactive bladder was suspected as the cause of the marked visualization of BAT in this patient.