Effects of Abnormal Thyroid Function Status to Bone Metabolism

ABSTRACT

Thyroid hormone plays an important role in bone remodeling. In overt hyperthyroidism, excess thyroid hormone accelerates bone turnover and shortens the normal bone remodeling cycle, leading osteoporosis and increased fracture risk. Several population and case-control studies have demonstrated that a prior history of hyperthyroidism is an independent risk factor for hip and vertebral fracture. In contrast, bone remodeling cycle is prolonged to almost 2 years with an increase in mineralized cortical bone in overt hypothyroidism. Some cross-sectional and longitudinal studies have suggested that thyroid hormone replacement could decrease bone mineral density in overt hypothyroidism. However, this effect might be interpreted as an adaptive mechanism on decreased bone turnover in preexistent hypothyroidism, and not as thyroid hormone induced bone loss. The effect of thyroid hormone replacement for hypothyroidism on fracture risk has not been investigated well. However, excessive thyroid hormone treatment might be increased the risk of fracture.