Calcitonin
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Salmon calcitonin peptide (32 amino acids) that inhibits osteoclast bone resorption; FDA-approved for osteoporosis, Paget's disease, and hypercalcemia, with unique analgesic properties for vertebral fracture pain.
Quick Facts
| Property | Value |
|---|---|
| Also Known As | Miacalcin, Fortical, salmon calcitonin, sCT, calcitonin-salmon |
| Category | Bone / Endocrine |
| Sequence | H-Cys-Ser-Asn-Leu-Ser-Thr-Cys-Val-Leu-Gly-Lys-Leu-Ser-Gln-Glu-Leu-His-Lys-Leu-Gln-Thr-Tyr-Pro-Arg-Thr-Asn-Thr-Gly-Ser-Gly-Thr-Pro-NH2 (disulfide bond between Cys1-Cys7) |
| Molecular Weight | ~3432 Da |
| Molecular Formula | C145H240N44O48S2 |
| PubChem CID | 16129616 |
| Administration | Intranasal spray (200 IU/day), SubQ, IM |
| Typical Dose Range | 200 IU/day intranasal; 50-100 IU SubQ/IM every other day |
| Half-Life | ~43 min (SubQ); ~18 min (IM); intranasal bioavailability ~3-5% |
| Storage | Refrigerated (2-8C) before opening; opened nasal spray stable at room temperature for up to 30 days |
| FDA Status | Approved (1984) — Miacalcin/Fortical for postmenopausal osteoporosis, Paget's disease, hypercalcemia of malignancy |
| WADA Status | Not prohibited (FDA-approved medication) |
Mechanism of Action
Calcitonin is a 32-amino-acid peptide hormone naturally produced by the parafollicular C cells of the thyroid gland. Salmon calcitonin is used therapeutically because it has 40-50 times greater potency than human calcitonin, owing to structural differences that confer higher receptor binding affinity and resistance to degradation.
Calcitonin exerts its primary skeletal effects by binding to the calcitonin receptor (CTR), a class B GPCR expressed at high density on osteoclasts. Receptor activation triggers Gs-coupled cAMP generation and Gq-coupled calcium signaling, leading to rapid osteoclast quiescence: the cells retract their ruffled border, cease acid secretion into the resorption lacuna, and detach from the bone surface. This produces an acute reduction in bone resorption markers (CTX, NTX) within hours of administration. However, the antiresorptive effect attenuates with chronic use due to receptor downregulation (CTR internalization), a phenomenon termed "escape" — osteoclasts resume resorption despite continued calcitonin exposure (PMID: 10996576).
Calcitonin also has a well-documented analgesic effect in acute osteoporotic vertebral fracture pain that appears independent of its antiresorptive action. The analgesic mechanism is not fully elucidated but likely involves central nervous system pathways: calcitonin receptors are expressed in brain regions involved in pain processing (periaqueductal gray, thalamus), and calcitonin may modulate endogenous opioid and serotonin systems (PMID: 21660557). This dual action — antiresorptive plus analgesic — is unique among osteoporosis therapies.
In the kidney, calcitonin promotes calcium and phosphate excretion, contributing to its efficacy in treating hypercalcemia of malignancy.
Key Research Areas
- Vertebral fracture prevention (PROOF trial) — The 5-year PROOF trial (n=1255) showed 33% vertebral fracture reduction with 200 IU/day intranasal calcitonin, though the anomalous dose-response (no effect at 100 or 400 IU) raised methodological concerns (PMID: 10996576)
- Acute vertebral fracture pain — Meta-analysis of 13 RCTs confirmed significant analgesic efficacy in acute osteoporotic vertebral compression fractures within 1-4 weeks, mediated through central opioid/serotonin pathways (PMID: 21660557)
- Cancer risk safety signal — 2013 FDA/EMA reviews identified a small but statistically significant increased cancer risk (OR ~1.2-2.4) in meta-analyses of calcitonin trials. EMA restricted nasal spray to short-term use only. Population cohort studies continue to evaluate this signal (PMID: 28981741)
- Paget's disease — Historical use for reducing bone turnover and pain in Paget's disease, largely replaced by bisphosphonates
Evidence Level Summary
| Evidence Type | Count | Notes |
|---|---|---|
| Systematic reviews | 1 | Pain meta-analysis (13 RCTs) |
| Human RCTs | 1 | PROOF trial (n=1255, 5-year) |
| Human observational | 1 | Cancer risk population cohort |
| Animal in vivo | 0 | — |
| In vitro | 0 | — |
Clinical Applications
- Osteoporosis — Postmenopausal osteoporosis (second/third-line; primarily for patients intolerant of bisphosphonates)
- Paget's disease — Reducing bone turnover and pain
- Hypercalcemia of malignancy — Acute management pending bisphosphonate onset of action
Protocols Using This Peptide
- No current vault protocols use calcitonin (FDA-approved prescription medication, not a research peptide)
Ageless Peps Products
- Not sold by Ageless Peps. Calcitonin is an FDA-approved prescription medication (Miacalcin/Fortical) available through licensed pharmacies.
Dosing Reference
FDA-Approved Dosing
| Indication | Dose | Route | Frequency | Duration | Source |
|---|---|---|---|---|---|
| Postmenopausal osteoporosis | 200 IU | Intranasal | Once daily (alternating nostrils) | Ongoing | FDA label |
| Postmenopausal osteoporosis | 100 IU | SubQ/IM | Every other day | Ongoing | FDA label |
| Paget's disease | 50-100 IU | SubQ/IM | Daily to every other day | 6-18 months | FDA label |
| Hypercalcemia of malignancy | 4-8 IU/kg | SubQ/IM | Every 6-12 hours | Short-term (days) | FDA label |
| Acute vertebral fracture pain | 200 IU | Intranasal | Daily | 2-4 weeks (EMA limit) | Clinical practice |
Cycling
Calcitonin is not typically cycled but has important duration considerations. The EMA (European Medicines Agency) restricted intranasal calcitonin to a maximum of 4 weeks for acute vertebral fracture pain in 2013, citing the cancer risk signal. The FDA did not impose a formal duration limit but advises weighing benefits against risks for long-term use. The phenomenon of "escape" (tachyphylaxis from receptor downregulation) also limits the practical utility of prolonged treatment, as antiresorptive efficacy attenuates after weeks to months of continuous use.
Contraindications & Safety
- Contraindications: Hypersensitivity to salmon calcitonin or any excipient (skin testing recommended before first SubQ/IM dose in patients with suspected fish allergy)
- FDA/EMA cancer safety review (2013): Meta-analysis of calcitonin trials showed a small but statistically significant increase in cancer incidence (OR ~1.2-2.4). EMA restricted nasal use to <=4 weeks. FDA maintained availability but recommends benefit-risk evaluation. No specific cancer type predominated; the mechanism is unclear (PMID: 28981741)
- Common side effects: Nasal: rhinitis, epistaxis, nasal dryness; Injectable: nausea, facial flushing, injection site reactions, diarrhea
- Drug interactions: No clinically significant drug interactions documented
- Pregnancy/nursing: Category C; use only if clearly needed
- Special populations: Dose reduction may be needed in renal impairment; salmon-origin product — rare anaphylaxis possible
Synergistic Combinations
- Calcium + Vitamin D — Essential co-supplementation (as in PROOF trial: 1000 mg Ca + 400 IU D daily)
- Calcitonin is generally used as monotherapy or as a bridge before initiating bisphosphonate or denosumab therapy
Related Research
| PMID | Title | Year | Study Type |
|---|---|---|---|
| 10996576 | PROOF Trial: Nasal Spray Salmon Calcitonin in Postmenopausal Osteoporosis | 2000 | RCT |
| 21660557 | Calcitonin for Acute and Chronic Pain of Osteoporotic Vertebral Compression Fractures | 2012 | Meta-analysis |
| 28981741 | Cancer Risk Associated with Calcitonin Use: Population-Based Cohort | 2017 | Cohort |
References
- PMID: 10996576 — Chesnut et al., Am J Med 2000 (PROOF trial)
- PMID: 21660557 — Knopp-Sihota et al., Osteoporos Int 2012 (pain meta-analysis)
- PMID: 28981741 — Sun et al., Jpn J Clin Oncol 2017 (cancer risk cohort)
Related
#peptide #fda-approved #not-sold #intranasal #subq