In humans, a link between steroid hormones and intergeneration inheritance has been postulated, however, the few data available on the specific contribution of testis-produced oestrogens to dysmetabolism come from a patient with Klinefelter’s syndrome (a condition with high prevalence of metabolic syndrome and increased incidence of type 2 diabetes mellitus) where increased aromatase expression has been localised to Leydig cells and Sertoli cells. The gene discussed is CYP19A1; the disease is Klinefelter syndrome.