BAT activity is greater in patients with phaeochromocytoma [53],[54] due to over-activity of the sympathetic nervous system and elevated levels of circulating catecholamines, that in turn stimulate β3 adrenergic receptors, thereby activating UCP1 expression via cyclic adenosine monophosphate (cAMP) and protein kinase-A (PKA) pathways [55]. The gene discussed is UCP1; the disease is pheochromocytoma.