parathyroid hormone at a glance
Medicine class
Full-length recombinant human parathyroid hormone replacement
Former licensed use
Add-on treatment for adults with chronic hypoparathyroidism inadequately controlled by standard therapy
Current availability
Natpar is discontinued; its UK marketing authorisation was withdrawn on 1 July 2026
What is parathyroid hormone used for?
Before withdrawal of its UK authorisation, Natpar had one licensed role:
Adjunctive treatment of adults with chronic hypoparathyroidism who could not be adequately controlled with standard therapy alone.
How does parathyroid hormone work?
It replaces missing full-length parathyroid hormone and activates parathyroid hormone receptors. This increases kidney calcium conservation, promotes phosphate excretion and supports activation of vitamin D, helping regulate calcium and phosphate balance.
parathyroid hormone preparations and strengths
Injection
Route: Parenteral
Strengths: 50 micrograms/dose, 75 micrograms/dose
parathyroid hormone side effects
Common or expected effects
- High or low blood calcium
- Headache
- Tingling or reduced skin sensation
- Diarrhoea or vomiting
- Increased calcium in the urine
- Muscle pain, twitching or cramps
- Injection-site redness or pain
Get urgent medical advice
- Seizures associated with very low calcium
- Severe muscle spasms, confusion or abnormal heartbeat from calcium disturbance
- Swelling of the face, lips, mouth or tongue, breathing difficulty, widespread rash or hives
parathyroid hormone in pregnancy
Information from human pregnancy is very limited. Anyone who becomes pregnant or is planning pregnancy while receiving parathyroid hormone requires prompt review by an endocrine and maternity specialist to balance maternal calcium control against uncertain fetal risk.
parathyroid hormone while breastfeeding
It is unknown whether parathyroid hormone passes into human milk, although animal studies found transfer into milk. A specialist should decide whether breastfeeding or treatment should continue after considering benefits and potential risks.
parathyroid hormone interactions
Calcium-changing medicines and medicines sensitive to calcium concentrations require particular review.
Digoxin or other digitalis medicines
Changes in blood calcium may alter susceptibility to digitalis toxicity, so clinical and biochemical monitoring is important.
Bisphosphonates, such as alendronic acid
Their effects on bone may oppose part of parathyroid hormone's calcium-regulating action.
Calcium and active vitamin D preparations
Requirements may change and must be guided by calcium monitoring to avoid high or low calcium.
Common questions about parathyroid hormone
Answers are fully visible for fast scanning and source review.
What was parathyroid hormone used for in the UK?
Natpar was licensed as add-on treatment for adults with chronic hypoparathyroidism that standard therapy alone could not adequately control.
Is Natpar still available in the UK?
No. It is discontinued, and its UK marketing authorisation was withdrawn on 1 July 2026.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.