[Summary] Epidemiologic evidence favors strong correlations between low thyrotropin(TSH) and high bone turnover, low bone mineral density ( BMD), and high fracture risk in hyperthyroid patients. Even subclinical hyperthyroidism, in which TSH is low and thyroid hormones are normal, is associated with osteopenia and osteoporosis. These evidences indicate that action of TSH on bone metabolism is independent of thyroid hormones and thus support the theory of the pituitary-bone axis. TSH plays its osteoprotective effect by binding TSH receptor on osteoclasts and inhibiting TNF-α expression. Physicians should screen the BMD in patients with overt and subclinical hyperthyroidism, especially the elderly, and make early diagnosis and better management for the underlying osteopenia and osteoporosis.