What is the role of calcitonin (thyrocalcitonin) in the body?

From the Guidelines

Calcitonin plays a crucial role in the body by regulating calcium levels and inhibiting bone resorption, primarily through its action on osteoclasts, and is used in the treatment of osteoporosis, Paget's disease of bone, and hypercalcemia. The hormone is produced by the thyroid gland's parafollicular C cells and is available as a medication in both nasal spray and injectable forms. According to a study published in 2011 1, calcitonin has been shown to be effective in reducing pain in patients with symptomatic osteoporotic spinal compression fractures. The typical dose for postmenopausal osteoporosis is 200 IU daily as a nasal spray, while injectable calcitonin is given at 100 IU daily or every other day subcutaneously or intramuscularly.

Key Points About Calcitonin

• Calcitonin works by directly inhibiting osteoclast activity, reducing bone breakdown and helping maintain bone density.
• Common side effects include nasal irritation with the spray form and nausea, flushing, and injection site reactions with injectable forms.
• The medication has largely been replaced by newer osteoporosis treatments due to concerns about a potential small increased risk of cancer with long-term use.
• Calcitonin remains useful for short-term pain management in acute vertebral fractures and for treating hypercalcemia when other options aren't suitable, as noted in a study on the treatment of symptomatic osteoporotic spinal compression fractures 1.
• A study published in 2003 1 discussed the use of calcitonin in patients with kidney disease, highlighting its potential benefits in preserving bone mass.

Clinical Use of Calcitonin

• For osteoporosis, calcitonin can help maintain bone density and reduce the risk of fractures.
• In Paget's disease of bone, calcitonin can help reduce bone resorption and alleviate symptoms.
• For hypercalcemia, calcitonin can help lower calcium levels in the blood.
• The use of calcitonin in patients with kidney disease has shown promise in preserving bone mass, as discussed in a study published in 2003 1.

From the FDA Drug Label

Calcitonin acts primarily on bone, but direct renal effects and actions on the gastrointestinal tract are also recognized. Animal studies indicate that endogenous calcitonin, primarily through its action on bone, participates with parathyroid hormone in the homeostatic regulation of blood calcium Thus, high blood calcium levels cause increased secretion of calcitonin which, in turn, inhibits bone resorption. The actions of calcitonin on bone and its role in normal human bone physiology are still not completely elucidated, although calcitonin receptors have been discovered in osteoclasts and osteoblasts.

The role of calcitonin (thyrocalcitonin) in the body is to:

• Regulate blood calcium levels by inhibiting bone resorption, which reduces the transfer of calcium from bone to blood
• Act on bone to decrease the rate of bone resorption and increase bone formation
• Participate in homeostatic regulation of blood calcium, in conjunction with parathyroid hormone
• Have direct renal effects and actions on the gastrointestinal tract, although the importance of these effects in humans has not been determined 2 2

From the Research

Role of Calcitonin in the Body

• Calcitonin is a peptide hormone secreted by the C-cells of the thyroid gland that plays a major role in protecting the skeleton against resorption in humans 3.
• It opposes the resorptive actions of parathyroid hormone and 1,25 dihydroxyvitamin D, making it a useful therapeutic agent in diseases where increased bone resorption is a major component 3.

Effects on Bone Health

• Calcitonin has been shown to preserve or increase bone mineral density (BMD) and reduce the risk of vertebral fractures in osteoporosis 4, 5, 6.
• It has a direct analgesic effect on bone pain, making it useful in improving pain from acute vertebral fractures of osteoporosis, Paget's disease, bone malignancies, and other sources of musculoskeletal pain 4, 7.
• Calcitonin can prevent postmenopausal bone loss and increase bone density in those with established osteoporosis 5, 6, 7.

Therapeutic Uses

• Calcitonin is used in the treatment of osteoporosis, Paget's disease of bone, and other bone diseases where resorption of bone is a component 4, 5, 6, 7, 3.
• It may be effective in preventing fractures, although current evidence for long-term prevention of fractures is limited 5, 7.
• Calcitonin has a potent analgesic effect in established osteoporosis, making it a useful alternative for osteoporotic women who refuse estrogens or for whom estrogens are contraindicated 6.