Study population

The design and operation of this study have been described [22]. Briefly, a total of 1096 urban postmenopausal Chinese women were recruited at random. Subjects with any pathological disorders (such as diabetes mellitus, hyperthyroidism, oligomenorrhoea, malabsorption, rheumatoid arthritis or hepatic dysfunction) or subjects using medications (such as glucocorticoids, bisphosphonate, oestrogen, thyroid hormones or statins) known to alter bone metabolism were excluded from our study. Of these, 232 subjects had to be excluded. 15 women were excluded due to lacking of time. Fourteen subjects had to be excluded because of impaired renal function (eGFR < 60 ml/min/1.73m²) [23]. After excluding 59 participants with abnormal laboratory test results, 776 qualifying healthy postmenopausal women were selected. All subjects agreed to participate in the study and gave written informed consent. The study was approved by the ethics committee of the Second Xiangya Hospital of Central South University (Changsha, China) and was in compliance with the Helsinki Declaration.