It is well known that obesity is associated with increased bone mineral density. Although this phenomenon has been explained to be attributable to the mechanical burden, there have been increasing evidences indicating that some humoral factor ie. 'hormone', especially adiposity signal such as insulin or leptin, may play a role in disorders of bone metabolism associated with obesity. There have been several evidences suggesting that other hormones such as thyroid hormone, growth hormone, or glucocorticoid may also be involved.