Calcitonin treats osteoporosis by binding to the osteoclasts (bone cells that build mineralization) and inhibiting mineral resorption to the bloodstream. It is a protein (actually a polypeptide 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. The FDA has approved calcitonin for administration by the subcutaneous, intramuscular, and intranasal routes. The bioavailability of nasal calcitonin is only about 25 percent that of intramuscular calcitonin.
Calcitonin can be used for treatment of high calcium levels (hypercalcaemia) and osteopenia. It is also effective in treatment of established osteoporosis, but it 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. Two studies found that calcitonin had no beneficial effect outside the spine, but other studies have shown improvement.
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 agent for osteoporosis treatment.
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 bread 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.