Patients were randomly allocated into two treatments groups (A and B) using a computer-generated random table. Group A received oral letrozole (2.5 mg/day, Femara, Novartis PharmaServices, Basel, Switzerland) and group B received goserelin subcutaneosly (3.6 mg/month, Zoladex@, Zeneka Pharma International, UK) for 12 weeks. Because, for technical reasons, GnRHa was supplied in vials and aromatase inhibitor in tablets, a double-blind study design was not feasible. Instead an assessor-blind design was chosen, whereby preparation and administration were performed by a person who did not take part in any decision concerning medication administration during the study. The study was approved by the ethics committee of the university and institutional Review Board (IRB), and each subject provided written informed consent before participating in the study. All subjects underwent baseline measurement, performed in the early follicular phase.