BAT activation, including browning of WAT to form beige adipocytes, can be induced by multiple factors including thyroxine, bile acids and factors overexpressed in certain malignant tumours, including interleukin 6 (IL-6), parathyroid hormone-related peptide (PTH-rP), fibroblast growth factor 21 and natriuretic peptides (Villarroya & Vidal-Puig 2013, Abdul Sater et al. 2020). The gene discussed is FGF21; the disease is cancer.