Large amounts of experimental and animal evidence have confirmed that iron accumulation is associated with bone loss. However, it is still lack of the clinical studies relating iron accumulation to bone loss, especially in the pathological conditions during our Chinese. In this study, the investigators aim to assess the association between the levels of serum ferritin and bone mineral density in Chinese healthy postmenopausal women.

For the past few years, an increasing number of in vitro studies show the association of iron accumulation with bone loss, particularly in postmenopausal women. And body iron accumulation is accurately reflected by levels of serum ferritin in clinic. The levels of serum ferritin among healthy women are about 13-150μg/L, and we give a definition of iron accumulation when serum ferritin range from 500μg/L to 1000 μg/L. How will the bone mineral density change in iron accumulation? The investigators intend to perform this study to explore and establish the relational function and logical function between serum ferritin, bone mineral density and biochemical markers of bone metabolism in Chinese healthy postmenopausal women.

Inclusion Criteria:

1. healthy postmenopausal women
2. subjects aged 55 years or older

Exclusion Criteria:

1. subjects with acute or chronic inflammatory or infectious diseases
2. chronic liver or renal diseases
3. history of transfusion or iron therapy in the previous year
4. history of drug therapy such as bisphosphonates and glucocorticoids, which might have affected bone metabolism
5. subjects with hematonosis

The study population consists of postmenopausal women aged 55 years or older who shall undergone comprehensive routine health examinations at the Second Affiliated Hospital of Soochow University, and on whom BMD, serum ferritin concentrations and bone turnover markers will be measured.The visitors are usually healthy and receive extensive screening tests for early detection of malignancy, diabetes, osteoporosis, and other age-related disease.