From the Guidelines
Calcitonin has immediate effects on calcium regulation, reducing serum calcium levels by inhibiting osteoclast activity, and prolonged effects including continued suppression of bone resorption, making it useful for treating conditions like Paget's disease and osteoporosis, although its effectiveness diminishes over time due to tachyphylaxis 1.
Immediate Effects
The immediate effects of calcitonin include:
- Reduction of serum calcium levels by inhibiting osteoclast activity in bones
- Decrease in bone resorption and calcium release into the bloodstream
- Enhancement of calcium excretion by the kidneys
- Reduction of calcium absorption in the intestines These effects typically begin within minutes to hours after administration, as noted in studies on its use in osteoporosis treatment 1.
Prolonged Effects
The prolonged effects of calcitonin include:
- Continued suppression of bone resorption
- Potential increase in bone mineral density over time with regular use
- Relief from osteoporotic bone pain, as suggested by a study on its use in symptomatic osteoporotic spinal compression fractures 1 However, the effectiveness of calcitonin tends to diminish over time due to the development of antibodies and receptor downregulation, a phenomenon known as tachyphylaxis.
Administration and Side Effects
Calcitonin is available as a nasal spray (typically 200 IU daily) or as subcutaneous or intramuscular injections (50-100 IU daily) 1. Side effects may include:
- Nausea
- Facial flushing
- Local reactions at injection sites
- Nasal irritation and rhinitis for nasal formulations Despite these effects, calcitonin is considered safe and devoid of serious or long-term side effects, although its use has declined in recent years due to concerns about its efficacy compared to newer osteoporosis treatments and potential cancer risks with long-term use 1.
Clinical Use
Given the current evidence, calcitonin should be used with caution and considered for patients with less serious osteoporosis who cannot tolerate other treatments 1. Its use in clinical practice should be guided by the most recent and highest quality evidence available, taking into account the potential benefits and risks for each individual patient.
From the FDA Drug Label
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. Single injections of calcitonin cause a marked transient inhibition of the ongoing bone resorptive process. With prolonged use, there is a persistent, smaller decrease in the rate of bone resorption In vitro studies have shown that calcitonin-salmon causes inhibition of osteoclast function with loss of the ruffled osteoclast border responsible for resorption of bone. There is some evidence from the in vitro studies that bone formation may be augmented by calcitonin through increased osteoblastic activity.
The immediate effects of calcitonin include:
- Inhibition of osteoclast function
- Transient inhibition of bone resorption
- Rapid and sustained small decreases in serum calcium
The prolonged effects of calcitonin include:
- Persistent decrease in the rate of bone resorption
- Increased spinal bone mass in post-menopausal women with established osteoporosis
- Formation of normal bone, as indicated by bone biopsy and radial bone mass studies 2, 2
From the Research
Immediate Effects of Calcitonin
- Calcitonin has an immediate effect on decreasing osteoclast activity, which can be demonstrated in vivo and in vitro 3.
- It can decrease serum calcium levels, with 75% of hypercalcemic patients exhibiting a clinically significant decrease in serum calcium within 2 hours of administration 4.
- Calcitonin can also have a direct analgesic effect on bone pain, improving pain in patients with osteoporosis, Paget's disease, and other sources of musculoskeletal pain 5.
Prolonged Effects of Calcitonin
- Long-term use of calcitonin can increase bone mineral density (BMD) and reduce the risk of vertebral fractures in osteoporosis 3, 5, 6.
- Calcitonin therapy has been shown to stabilize and in some cases produce a short-term increase in bone density at the lumbar spine level 6.
- The Prevent Recurrence of Osteoporotic Fractures (PROOF) study found that salmon calcitonin nasal spray at a dosage of 200 IU/day can reduce the risk of vertebral osteoporotic fractures by 33% 6.
- Calcitonin may also play a role in the prevention and recovery of maternal bone loss during pregnancy and lactation, by increasing the transfer of maternal calcium to the fetus/infant 7.
Side Effects and Tolerability
- The most common side effects of calcitonin are nausea and vomiting, which occur in approximately 12.5% of patients 4.
- Calcitonin is generally well-tolerated, with the intranasal formulation being the most widely used due to its improved tolerability 6.
- Calcitonin-induced hypocalcemia is rare, and the drug can be used safely alone or in conjunction with other hypocalcemic therapies 4.