Osteoporosis is the most common metabolic bone disorder that is characterized by reduction of bone mass without alteration in the composition of bone, leading to fractures. The most obvious subclinical symptom of this disorder is the fracture in the vertebral and femoral neck bone . Osteoporosis cause approximately 2 million fractures annually, which decrease quality of life, increased disability and even death . The National Osteoporosis Foundation estimated that approximately 45 million persons over the age of 50, in 2002, in the United States were at risk for fracture due to osteoporosis and they estimated that in 2020, that number is over 60 million . The osteoporosis has a complex and heterogenic nature the cause of which is not yet known. The known risk factors for osteoporosis are menopause, age, family history of fracture, race, immobility, smoking, corticosteroids, and deficiency of some nutrients such as calcium and vitamin D [4, 5]. The effect of some extrinsic causes of osteoporosis, including genetic disorders, autoimmune diseases (e.g. lupus, rheumatoid arthritis and etc.) endocrine disorders (e.g. Diabetes Mellitus (DM), Cushing’s syndrome, hypothyroidism and hyperparathyroidism) gastrointestinal disorders (e.g. celiac disease, gastric bypass, GI surgery, inflammatory bowel disease, pancreatic disease and cirrhosis), and hematologic disorders (e.g. hemophilia, sickle cell disease and thalassemia) are not well known .
DM is accompanied by a comprehensive list of chronic complications that affect almost all tissues. Musculoskeletal complications in DM have been identified since the beginning of the 20th century . As DM and osteoporosis are prevalent and have especial socio-economic importance in society, the evaluation of the interaction of these two diseases has been recognized even more. The important question is that whether DM is a risk factor for osteopenia and osteoporosis, or these disorders are complication of DM. However, the results of bone mineral density (BMD) in type II DM are different and sometimes contrary [8–11]. In some studies no difference has been observed in BMD between patients with type II DM and healthy individuals. A number of studies have reported lower BMD in type II diabetic patients than normal population, while there are still others in which the BMD has been higher in diabetics in comparison with normal population .
The most common causes of secondary osteoporosis can be mentioned as follows: increase endogenic and exogenous glucocorticoids, hyperthyroidism, hyperparathyroidism, and vitamin D deficiency [12–19]. Hyperthyroidism causes bone erosion which has been reported to be an important reason for the increase in the brittleness of collagenase tissue, as well as the decrease in BMD. The role of thyroid hormones in bone metabolism is not identified, but the impact of T3 on osteoclasts has been suggested in bone erosion . As the role of DM and thyroid dysfunctions in the prevalence of osteoporosis is not exactly known, therefore this study was designed to evaluate the probable association between osteoporosis with DM and thyroid dysfunctions among subjects referring to Gorgan bone densitometry centers, north-east of Iran.