What are the immediate and prolonged effects of calcitonin (Calcitonin)

From the Guidelines

Calcitonin has both immediate and prolonged effects on calcium regulation in the body, and its use is recommended as a second-line treatment for osteoporosis when other medications aren't tolerated or for short-term pain management in vertebral fractures, as evidenced by the most recent study 1. The immediate effects of calcitonin include reducing serum calcium levels by inhibiting osteoclast activity in bones, which decreases bone resorption and calcium release into the bloodstream. It also enhances calcium excretion by the kidneys and reduces calcium absorption in the intestines. These immediate effects typically begin within minutes to hours after administration. Some key points to consider when using calcitonin include:

• The prolonged effects of calcitonin include continued suppression of bone resorption, which can lead to increased bone mineral density over time with regular use, as shown in a study on symptomatic osteoporotic spinal compression fractures 1.
• Calcitonin is typically administered as salmon calcitonin (Miacalcin, Fortical) at doses of 100-200 IU daily via nasal spray or subcutaneous injection.
• Side effects may include nausea, facial flushing, and allergic reactions, with mild dizziness also reported in some studies 1.
• The effectiveness of calcitonin for long-term use may diminish over time due to antibody formation and receptor downregulation, a phenomenon known as tachyphylaxis.
• Other treatment options, such as bisphosphonates, raloxifene, and denosumab, may be preferred as first-line therapies for osteoporosis, as recommended in a practice bulletin on osteoporosis 1.
• Calcitonin may also be used to treat hypercalcemia, often in combination with other medications such as bisphosphonates, steroids, and hydration/furosemide, as suggested in guidelines for multiple myeloma 1.

From the FDA Drug Label

Calcitonin acts primarily on bone, but direct renal effects and actions on the gastrointestinal tract are also recognized. 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. Histologically, this is associated with a decreased number of osteoclasts and an apparent decrease in their resorptive activity. 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.

The immediate effects of calcitonin include:

• Marked transient inhibition of the ongoing bone resorptive process
• Rapid and sustained small decreases in both total serum calcium and serum ionized calcium
• Transient decreases in the volume and acidity of gastric juice and in the volume and the trypsin and amylase content of pancreatic juice

The prolonged effects of calcitonin include:

• Persistent, smaller decrease in the rate of bone resorption
• Decreased number of osteoclasts and an apparent decrease in their resorptive activity
• 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

From the Research

Immediate Effects of Calcitonin

• Calcitonin has a rapid onset of action, with a pronounced hypocalcemic effect observed in most patients within a short period of treatment 3, 4
• The immediate effects of calcitonin include a decrease in serum calcium levels, which can lead to clinical amelioration in patients with hypercalcemia 3
• Calcitonin can also increase creatinine clearance and decrease serum creatinine levels, indicating an improvement in renal function 3

Prolonged Effects of Calcitonin

• The prolonged use of calcitonin can lead to a sustained decrease in serum calcium levels, although its efficacy in normalizing serum calcium levels is generally considered poor compared to other treatments like bisphosphonates 5
• Calcitonin may be used in combination with other treatments, such as bisphosphonates, to enhance its hypocalcemic effect and provide a more rapid reduction in serum calcium levels 5, 4
• The prolonged use of calcitonin is generally well-tolerated, with few serious side effects reported 3, 5

Comparison with Other Treatments

• Bisphosphonates are generally more potent than calcitonin in reducing serum calcium levels, but they have a delayed onset of action 5, 4
• Denosumab has been shown to be effective in reducing serum calcium levels in patients with severe hypercalcemia due to primary hyperparathyroidism, and may be used as a bridge to surgery 6
• Glucocorticoids may be effective in patients with hypercalcemia associated with high levels of vitamin D, such as sarcoidosis or vitamin D intoxication 4