Parathyroid hormone

Peptide Hormone / Calcium Regulating HormoneRx: PrescriptionCompound: Approved

Also known as: Natpar, Natpara, parathormone, PTH, PTH(1-84), rhPTH(1-84)

Educational Only — Not medical advice. Consult a qualified clinician before using any peptide.

Summary

Parathyroid hormone (PTH) is an 84-amino-acid peptide secreted by the parathyroid glands that is the primary regulator of calcium and phosphate homeostasis. Recombinant human PTH 1-84 (rhPTH[1-84]) is approved as Natpara/Natpar for hypoparathyroidism. The truncated 1-34 fragment (teriparatide) is separately approved for osteoporosis. Endogenous PTH excess leads to hypercalcemia and bone loss, while deficiency causes hypocalcemia.

Mechanism of Action

Binds to PTH1 receptors (PTH1R) on osteoblasts and renal tubular cells, activating adenylyl cyclase and PKA signaling. Stimulates osteoblast activity (anabolic at intermittent dosing), increases renal calcium reabsorption and phosphate excretion, and promotes renal synthesis of 1,25-dihydroxyvitamin D (calcitriol), thereby raising serum calcium and regulating bone metabolism.

Routes of Administration

Subcutaneous

Goals & Uses

  • Serum calcium normalizationMetabolicHigh
  • Bone anabolism / osteoporosis managementMusculoskeletalHigh
  • Treatment of hypoparathyroidismEndocrine / Calcium HomeostasisHigh
  • Reduction of supplemental calcium/vitamin D burdenQuality Of LifeModerate

Contraindications

  • Conditions predisposing to osteosarcoma (e.g., Paget's disease, prior radiation to skeleton, open epiphyses)Oncologic / SkeletalHigh
  • Hypersensitivity to rhPTH or excipientsAllergic / ImmunologicHigh
  • Pre-existing hypercalcemiaMetabolicHigh
  • Malignancy or skeletal metastasesOncologicHigh
  • Pediatric patients with open epiphysesPediatricHigh

Adverse Effects

  • HypercalcemiaMetabolicCommon
  • Injection site reactionsLocalCommon
  • HeadacheNeurologicCommonPain in the head or upper neck
  • NauseaGastrointestinalCommonFeeling of sickness or urge to vomit
  • OsteosarcomaOncologyRare
  • Hypocalcemia (upon discontinuation)MetabolicCommon

Drug Interactions

  • Active vitamin D analogs (e.g., calcitriol)Moderate
  • DigoxinHigh
  • Calcium supplementsLow
  • Thiazide diureticsModerate

Population Constraints

  • Pediatric patientsAgeAbsolute
  • Lactating womenReproductiveRelative
  • Elderly patientsAgeRelative
  • Pregnant womenReproductiveRelative
  • Patients with renal impairment (severe, CrCl <30 mL/min)RenalRelative

Regulatory Status

  • European UnionApprovedApproved: Hypoparathyroidism in adultsApproved by EMA under brand name Natpar. Similar risk restrictions as US approval.
  • United StatesApprovedApproved: Hypoparathyroidism (adjunct to calcium and vitamin D supplementation in adults)Approved by FDA in January 2015 under brand name Natpara. Subject to REMS due to osteosarcoma risk. Duration of use limited to 2 years.
  • United KingdomApprovedApproved: Hypoparathyroidism in adultsApproved via EMA prior to Brexit; MHRA has maintained recognition post-Brexit.

rhPTH(1-84) (Natpara/Natpar) approved by FDA (2015) and EMA for hypoparathyroidism. Carries a Boxed Warning for osteosarcoma risk (based on rat data); use limited to 2 years. REMS program required in the US.

Evidence & Sources

No sources recorded yet.

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