Moreover, a rare inactivating mutation of ESR1 (the gene encoding ERα) was shown to produce metabolic dysfunction in a middle-aged man,2,3,4,5 and male mice with a homozygous Cyp19 (encodes aromatase) or Esr1 null deletion mutation recapitulate many clinical features of metabolic syndrome.6 This evidence concerns the gene CYP19A1 and metabolic syndrome.