**2.4 Blood samples**

Blood samples were collected from 34 patients with histologically proven EC. Once the patient was anaesthetised, 10 ml of central venous blood was taken using gold-top Vacutainer Serum Separation Tubes (BD Vacutainer® SST™). Blood samples were immediately transported to the Clinical Chemistry laboratory in Royal Derby Hospital for analysis. Fasting serum level of testosterone, luteinizing hormone (LH), follicle stimulating hormone (FSH), sex hormone binding globulin (SHBG), 17-β oestradiol (E2) were measured using *ElectroChemiLuminescence ImmunoAssay* (ECLIA, Roche) and as per manufacturer's protocols. *Elecsys and Cobas e immunoassay 411 analyzer* was used for running of ECLIA (Roche-diagnostic, USA). The free androgen index (FAI) was calculated as the total testosterone to SHBG ratio [28].
