Serum cytokines and bone metabolism in patients with thyroid dysfunction

Hyperthyroidism is associated with increased bone turnover. Besides the hormones of calcium metabolism, locally produced factors are important in maintaining normal bone metabolism. Interleukin-6 (IL-6), in particular, has a major influence on bone turnover. In this study, serum IL-6 and tumor necrosis factor-alpha (TNF-alpha) levels, as well as bone turnover markers and relationships between them, were investigated in hyperthyroidism and hypothyroidism. A total of 20 female patients with hyperthyroidism, 15 with subclinical hyperthyroidism, 16 with hypothyroidism, and 15 with subclinical hypothyroidism constituted the patient groups. In all, 15 age-matched healthy female volunteers were recruited as controls. When compared with controls, serum TNF-alpha levels showed no significant difference in any of the patient groups (P>.05). In the groups with hyperthyroidism and subclinical hyperthyroidism, IL-6 levels were significantly higher compared with control group values (P<.05). Hyperthyroid patients showed higher levels of alkaline phosphatase (ALP) and osteocalcin, and a higher urinary deoxypyridinoline/creatinine ratio, compared with controls (P<.05). In subclinical hyperthyroidism, only ALP was found to be higher compared with control values. No significant correlations were made in any group between serum IL-6 or TNF-alpha level and bone turnover markers. Results suggest that serum IL-6 level and markers of bone turnover rate seem to be increased in hyperthyroidism. This finding may support the role of IL-6 in induction of bone turnover in hyperthyroid states.