Calcitonin treats osteoporosis by binding to the osteoclasts (bone cells that build mineralization) and inhibiting mineral resorption to the bloodstream. It is a protein (composed of 32 amino acids) and is produced in the thyroid. The body uses it as part of a homeostatic control system in combination with parathyroid hormone.
As a drug, the calcitonin can be taken from other animals - salmon calcitonin is the one most widely used. It is highly potent in humans because of its high affinity (forty times that of human calcitonin) for the human calcitonin receptor and its slow rate of clearance. Human calcitonin is sometimes used; it is less effective but less apt to produce a negative reaction from the patient’s body. Traditionally calcitonin has come in subcutaneous, intramuscular, and intranasal forms. Oral formulations have been recently developed.
Calcitonin can be used for treatment of high calcium levels (hypercalcaemia) and osteopenia. It is also effective in treatment of full-blown osteoporosis, but is used less often than other drugs. Calcitonin is less effective for the treatment of postmenopausal osteoporosis than bisphosphonates.
There are conflicting data on the effect of calcitonin on skeletal sites other than the spine.
Calcitonin can relieve pain in patients who have sustained a fracture, although experts don't understand the mechanism behind the pain mitigation. Some doctors give calcitonin to osteoporosis patients if pain is a problem, and then switch to other methods such as bisphosphonates once the pain has subsided.
Indeed, calcitonin is generally considered a second-line or third-line agent for osteoporosis treatment. Some have suggested it is appropriate for elderly patients because of its benign safety profile. However, a big concern is that long-term use of calcitonin increases the risk for cancer.
An early theory held that a deficiency in the body’s natural calcitonin contributed to osteoporosis but that turned out not to be true. Mice bred to remove the calcitonin gene actually have higher bone density than normal mice.
Dietary magnesium stimulates the body's production of calcitonin. Getting enough magnesium can help lower the risk of heart attack, kidney stones, and osteoporosis.