FGFR1 and Insulin resistance: After challenge with a high‐fat diet, however, these mice show hyperglycaemia and insulin resistance, likely as a result of the critical regulation of adipose tissue by FGF1.57 Mice carrying a gain‐of‐Fgfr1 function mutation appear normal,58 although those with a gain‐of Fgfr2 mutation are hypoglycaemic and show growth retardation and early death.59 Fortunately, a plethora of conditional loss and gain of function alleles for these and other FGFs and FGFRs have been developed to circumvent embryonic/neonatal lethality.