Calcitonin is a polypeptide hormone of thyroid origin that inhibits bone resorption by osteoclasts. Salmon calcitonin is available in injectable form and as nasal spray. At the dose of 200 IU nasal spray QD, salmon calcitonin reduces the risk of vertebral fracture in late postmenopausal women with osteoporosis. Nasal calcitonin produces small increments in bone mass of the spine and modest decreases in bone turnover. No significant effect on non-vertebral fracture has been observed.