Hypocalcemia Is a Common Risk Factor for Osteoporosis in Taiwanese Patients with Cushing's Syndrome

Background: Osteoporosis is a cardinal manifestation of Cushing’s syndrome. There is a lack of relevant research on risk factors for osteoporosis among patients with Cushing’s syndrome (CS) in Taiwan. Thus, this study was designed to explore the possible risk factors of osteoporosis. Methods: We gathered patients with a diagnosis of CS between 2001 and 2017 in the Chang Gung Research Database (CGRD). We extracted data including diagnoses and biochemistry from hospital records. The diagnosis of CS was based on ICD-9-CM codes (255.0). Osteoporosis was defined by a T value equal to or less than −2.5 in BMD examination and hypocalcemia was defined as serum calcium concentrations < 8.0 mg/dL. Results: A total of 356 patients with CS who made regular visits to the outpatient department were enrolled in this study. The mean age was 68.6 years, and 74.9% of the patients were female. Of them, 207 patients (58.1%) were diagnosed with osteoporosis. Multivariable logistic regression models indicated that serum calcium level was negatively associated with osteoporosis (OR 0.70, CI 0.54−0.91, p < 0.001) after adjustment for age, sex, and other confounding risk factors. In addition, hypocalcemia was associated with heart failure (HF) (OR 2.14, CI 1.02−4.47, p < 0.05), stroke (OR 2.58, CI 1.21−5.46, p < 0.05) and osteoporosis (OR 3.04, CI 1.24−7.41, p < 0.05) in multivariate analysis. Conclusions: Our study found that lower serum calcium levels were common among patients with CS and osteoporosis. Furthermore, CS patients with HF or stroke had high proportion of hypocalcemia. Therefore, these patients must pay more attention to adequate calcium supplementation and undergo the appropriate osteoporosis drug treatment to reduce the risk of subsequent fracture and disability.