2.1 Study population and design
We performed a cross-sectional study among communities in Guangzhou,
China, from March to July, 2015. This study population was obtained from
the research project of the National Health and Family Planning
Commission of China, titled-”National Survey of Thyroid Diseases and
Diabetes”. This project has been set up as a multicenter prospective
observational study aiming to evaluate chronic diseases in the Chinese
population. Inclusion criteria: 1) 18-79 years old; 2) The Han ethnicity
of the Chinese population; 3) Permanent residents, who lived in those
regions ≥5 years. Exclusion criteria: 1) Pregnant women; 2) Those who
suffer from severe diseases such as hepatic cirrhosis, chronic renal
failure or evident cardiac insufficiency; 3) individuals who received
medicines influencing thyroid function or hormones, such as iodine,
amiodarone, somatostatin and glucocorticoids, within the past three
months. A multistage stratified cluster random sampling method was used
to select a representative sample. In the first stage, the districts of
Guangzhou city were divided into rural areas and urban areas; In the
second stage, one rural area and one urban area were randomly selected;
In the third stage, one community was sampled from both rural and urban
groups using a random selection; Finally, one adult resident was
randomly selected from each household of the selected communities.
During the recruitment phase, a total of 2767 residents were invited to
participate via examination notices or home visits. In total, 2720
subjects signed the consent form and agreed to participate in the
survey. 1567 females and 155 male with missing information regarding ED
or osteoporosis were excluded. Finally, 998 eligible individuals were
included in the data analyses. The flow chart for data analysis is shown
in Figure 1 . All participants provided informed consent before
being recruited into the study. The study protocol was in accordance
with the principles of the Helsinki Declaration II and our study was
approved by the Ethics Committee of the Sun Yat-sen Memorial Hospital
(2014[3]).