What is the effect of calcitonin on vitamin D (Vit D) levels?

From the Guidelines

Calcitonin has minimal direct effects on vitamin D metabolism. Calcitonin is a hormone produced by the thyroid gland that primarily functions to decrease blood calcium levels by inhibiting bone resorption by osteoclasts and increasing calcium excretion by the kidneys. Unlike parathyroid hormone (PTH), which stimulates the conversion of vitamin D to its active form (1,25-dihydroxyvitamin D) in the kidneys, calcitonin does not significantly influence vitamin D activation or metabolism, as seen in studies where calcitonin was used to treat symptomatic osteoporotic spinal compression fractures, with patients receiving calcium and vitamin D separately 1. The regulation of vitamin D is mainly controlled by PTH, serum calcium and phosphate levels, and direct feedback mechanisms. While calcitonin and vitamin D both participate in calcium homeostasis, they do so through different pathways - calcitonin acts primarily on bone and kidneys to lower serum calcium, while vitamin D enhances calcium absorption from the intestines and promotes bone mineralization. Some key points to consider when evaluating the effects of calcitonin on vitamin D include:

• The primary mechanism of action of calcitonin is on bone resorption and renal calcium excretion, not on vitamin D metabolism 1.
• Studies using calcitonin for the treatment of osteoporotic spinal compression fractures have shown benefit in pain reduction, but these studies also involved the administration of calcium and vitamin D, indicating that vitamin D supplementation is considered necessary for bone health, independent of calcitonin therapy 1.
• The use of calcitonin in clinical practice, such as for osteoporosis, does not typically require adjustments to vitamin D dosages, further suggesting that calcitonin does not have a significant direct impact on vitamin D metabolism. Overall, the evidence supports the notion that calcitonin and vitamin D operate through distinct pathways in calcium homeostasis, with calcitonin not having a direct significant effect on vitamin D metabolism, as demonstrated in clinical studies 1.

From the FDA Drug Label

Use of Calcitonin Salmon Nasal Solution is recommended in conjunction with an adequate intake of calcium and vitamin D [see Dosage and Administration (2.3)]. Patients who use Calcitonin Salmon Nasal Solution should receive adequate calcium (at least 1000 mg elemental calcium per day) and vitamin D (at least 400 International Units per day). Other disorders affecting mineral metabolism (such as vitamin D deficiency) should also be effectively treated

Calcitonin affects vitamin D by requiring adequate intake of vitamin D during treatment with Calcitonin Salmon Nasal Solution.

• The recommended daily intake of vitamin D is at least 400 International Units per day.
• Vitamin D deficiency should be effectively treated before initiating therapy with Calcitonin Salmon Nasal Solution.
• Serum calcium and symptoms of hypocalcemia should be monitored during therapy with Calcitonin Salmon Nasal Solution 2, 2, 2.

From the Research

Calcitonin and Vitamin D Interaction

• Calcitonin inhibits the function of osteoclasts, reducing bone resorption, while vitamin D stimulates matrix formation and bone maturation but also enhances osteoclastic activity 3.
• The combination of vitamin D and calcitonin could result in a positive bone balance, as shown in a study where 13 women with postmenopausal osteoporosis received high doses of vitamin D and moderate doses of salmon calcitonin, resulting in a marked reduction in bone pain and a 43% increment in trabecular bone volume 3.

Vitamin D Status in Paget's Disease of Bone

• Vitamin D status in Paget's disease of bone (PDB) patients is not well defined, but studies suggest that hypovitaminosis D is frequent in PDB patients 4, 5.
• Serum levels of 1,25(OH)2D3 were increased in 48% of PDB patients, with markedly elevated levels found in five patients 4.
• Cholecalciferol treatment was effective in increasing 25OHD levels in PDB patients with hypovitaminosis D, reducing PTH, bone pain score, and pain medication score without changes in metabolic risk factors for nephrolithiasis 5.

Calcitonin and Vitamin D in Osteoporosis Treatment

• The combination of vitamin D and calcitonin has been shown to be beneficial in osteoporosis treatment, with a study demonstrating a prolonged beneficial effect of the combination of high doses of vitamin D with moderate doses of calcitonin in postmenopausal osteoporosis 3.
• Calcitonin can be used as an alternative treatment for patients with Paget's disease of bone who are intolerant of bisphosphonates, but its use is limited due to the associated risk of malignancy 6.