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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Parathyroid Hormone
Brand Name
Natpara (parathyroid Hormone)
Generic Name
Parathyroid Hormone
Active Ingredient
Parathyroid HormoneCategory
Parathyroid Hormone [EPC]
Variants
4
Different strengths and dosage forms
| Strength | Form | Route | NDC |
|---|---|---|---|
| 100 ug/.08mL | INJECTION, POWDER, LYOPHILIZED, FOR SOLUTION | SUBCUTANEOUS | 68875-0205 |
| 75 ug/.08mL | INJECTION, POWDER, LYOPHILIZED, FOR SOLUTION | SUBCUTANEOUS | 68875-0204 |
| 25 ug/.08mL | INJECTION, POWDER, LYOPHILIZED, FOR SOLUTION | SUBCUTANEOUS |
This page is for informational purposes only and does not replace medical advice. Before using any prescription or over-the-counter medication for Natpara (parathyroid Hormone), you must consult a qualified healthcare professional.
| 68875-0202 |
| 50 ug/.08mL | INJECTION, POWDER, LYOPHILIZED, FOR SOLUTION | SUBCUTANEOUS | 68875-0203 |
Detailed information about Natpara (parathyroid Hormone)
Parathyroid Hormone (rhPTH 1-84) is a recombinant human hormone used as an adjunct to calcium and vitamin D for the control of hypocalcemia in patients with hypoparathyroidism. It belongs to the Parathyroid Hormone [EPC] drug class.
The dosing of Parathyroid Hormone must be highly individualized to maintain the patient's serum calcium in the lower half of the normal range. According to clinical guidelines, the starting dose is typically 50 mcg once daily, administered subcutaneously in the thigh.
Before starting treatment, your healthcare provider will ensure your 25-hydroxyvitamin D stores are sufficient and that your serum calcium is above 7.5 mg/dL. When starting Parathyroid Hormone, the doses of active vitamin D and oral calcium supplements are usually reduced by 50% to prevent hypercalcemia (excessively high blood calcium). Your doctor will monitor your blood calcium levels frequently (e.g., every 3 to 7 days) during the initial titration phase and adjust the hormone dose in increments of 25 mcg every 4 weeks if necessary. The maintenance range is generally 25 mcg to 100 mcg once daily.
Parathyroid Hormone is NOT approved for use in pediatric patients. The safety and effectiveness in children and adolescents have not been established. There is a specific concern regarding the risk of osteosarcoma in pediatric populations, as their bones are still growing (open epiphyses). In animal studies, increased bone turnover in young rats led to a higher incidence of bone tumors.
No specific dose adjustment is required for patients with mild to moderate renal impairment. However, because Parathyroid Hormone affects renal calcium and phosphate handling, patients with significant kidney disease require close monitoring of their calcium-phosphate product to prevent soft tissue calcification.
No dose adjustment is required for patients with mild to moderate hepatic impairment (Child-Pugh Class A or B). The drug has not been studied in patients with severe hepatic impairment.
Clinical trials did not include sufficient numbers of patients aged 65 and over to determine if they respond differently than younger patients. In general, dose selection for an elderly patient should be cautious, starting at the low end of the dosing range.
If you miss a dose, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and return to your regular schedule. Do not take two doses on the same day. If you miss more than two consecutive doses, contact your healthcare provider, as your calcium levels may drop rapidly, requiring temporary increases in your oral calcium and vitamin D supplements.
Signs of overdose (hypercalcemia) include severe nausea, vomiting, constipation, muscle weakness, and confusion. In severe cases, it can lead to kidney stones or heart rhythm abnormalities. If an overdose is suspected, seek emergency medical attention immediately. Treatment typically involves vigorous hydration and discontinuation of the hormone until calcium levels stabilize.
> Important: Follow your healthcare provider's dosing instructions exactly. Do not adjust your dose or stop the medication without medical guidance, as sudden discontinuation can lead to life-threatening hypocalcemia.
In clinical trials, the most frequently reported side effects associated with Parathyroid Hormone therapy include:
Parathyroid Hormone is a high-alert medication that requires diligent monitoring. It is not a simple 'vitamin' but a potent hormone that fundamentally changes how your body handles minerals. Patients must be committed to regular blood testing and must understand the signs of both high and low calcium.
Full Text Summary: Parathyroid Hormone is associated with a potential risk of osteosarcoma. In animal studies (rats), the drug caused a significant increase in bone cancer. While this has not been confirmed in humans, the drug is only available through the Natpara REMS Program. Use is restricted to patients where the benefits clearly outweigh the risks of potential malignancy. It must be avoided in patients with Paget’s disease, unexplained elevations of alkaline phosphatase, or those who have had prior radiation therapy to the bones.
There are no absolute 'never use' drug-drug contraindications listed in the FDA labeling; however, the use of Teriparatide (Forteo) or other PTH analogs alongside Parathyroid Hormone is contraindicated because it would lead to an unpredictable and dangerous additive effect on calcium levels.
Parathyroid Hormone must NEVER be used in the following circumstances:
Parathyroid Hormone is classified as Pregnancy Category C (under the older FDA system). There are no adequate and well-controlled studies in pregnant women. Animal studies have shown some developmental delays in offspring when mothers were given high doses. In clinical practice, if a woman with hypoparathyroidism becomes pregnant, her calcium needs will change significantly, especially in the third trimester. Most experts recommend managing calcium with active vitamin D and calcium supplements rather than the hormone during pregnancy unless the condition is otherwise unmanageable.
It is unknown whether Parathyroid Hormone is excreted in human milk. Because many drugs are excreted in milk and because of the potential for serious adverse reactions in nursing infants (including effects on the infant's own calcium regulation), a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.
Safety and effectiveness have not been established in patients less than 18 years of age.
Parathyroid Hormone (rhPTH 1-84) is a bone-active agent that serves as a potent agonist at the PTH1 Receptor (PTH1R), a G-protein coupled receptor. Upon binding to PTH1R in bone and kidney tissues, it triggers two primary intracellular signaling pathways: the adenylate cyclase/cyclic AMP (cAMP) pathway and the phospholipase C/inositol triphosphate pathway.
In the kidney, this activation leads to increased expression of calcium transporters in the distal tubule (enhancing reabsorption) and down-regulation of phosphate transporters in the proximal tubule (enhancing excretion). In the bone, the hormone stimulates the RANKL pathway, which regulates the balance between bone resorption and formation. Unlike Teriparatide (which is only the 1-34 fragment), rhPTH 1-84 is the full-length molecule, which may have additional effects mediated by C-terminal PTH receptors, though the clinical significance of this is still being researched.
Following a single subcutaneous injection, serum calcium levels begin to rise within 2 hours and reach a peak effect at approximately 10 to 12 hours. The effect on calcium typically lasts for 24 hours, which is why once-daily dosing is standard. The drug also causes a rapid decrease in serum phosphorus levels. Over time, chronic administration helps stabilize the 'calcium-sensing' mechanism of the body, though it does not cure the underlying parathyroid gland failure.
Common questions about Natpara (parathyroid Hormone)
Parathyroid Hormone (specifically the rhPTH 1-84 form) is used as a long-term replacement therapy for adults with a rare condition called hypoparathyroidism. In this condition, the body does not produce enough natural parathyroid hormone, leading to dangerously low levels of calcium in the blood. The medication is used as an 'add-on' treatment when calcium and vitamin D supplements alone are not enough to keep calcium levels stable. It helps the kidneys retain calcium and helps the bones release calcium into the bloodstream. Because of its specific risks, it is only prescribed by specialists, such as endocrinologists.
The most common side effects include tingling or 'pins and needles' sensations (paresthesia), headaches, and nausea. Many patients also experience joint pain or muscle aches during the first few weeks of treatment. Fluctuations in blood calcium levels are common, which can cause either symptoms of low calcium (like muscle cramps) or high calcium (like thirst and fatigue). Most of these side effects are manageable with dose adjustments of the hormone or your calcium supplements. Always report new or worsening symptoms to your doctor immediately.
There is no known direct interaction between alcohol and Parathyroid Hormone; however, caution is advised. Alcohol can contribute to dehydration and can interfere with how your body absorbs nutrients, including calcium. Since maintaining a precise calcium balance is the goal of this therapy, heavy drinking could make your condition harder to manage. It is best to discuss your alcohol consumption with your doctor to ensure it does not interfere with your specific treatment plan. Moderate consumption is generally considered acceptable for most patients.
The safety of Parathyroid Hormone during pregnancy has not been established in humans. It is currently classified as a medication where the benefits must clearly outweigh the potential risks to the fetus. If you are pregnant or planning to become pregnant, your doctor will likely try to manage your hypoparathyroidism using only calcium and active vitamin D. This is because the hormone's effects on fetal bone development are not fully understood. If you do take it while pregnant, you will require very frequent blood monitoring as calcium needs change throughout pregnancy.
Parathyroid Hormone begins to raise blood calcium levels within about 2 hours after the first injection. However, it takes much longer to find the 'steady state' or the perfect dose for your body. Most patients undergo a titration period where the dose is adjusted every 4 weeks based on blood tests. It may take several months to achieve stable, consistent calcium levels and to reduce your reliance on high-dose oral supplements. You should not expect immediate 'perfection' in your labs, as the body needs time to adjust to the hormonal replacement.
No, you must never stop taking Parathyroid Hormone suddenly. Because your body cannot make its own parathyroid hormone, stopping the medication will cause your blood calcium levels to drop rapidly, often within 24 to 48 hours. This can lead to a medical emergency called 'tetany,' characterized by severe muscle spasms, seizures, or difficulty breathing. If you need to stop the medication for any reason, your doctor will provide a strict plan to increase your oral calcium and vitamin D doses to compensate for the loss of the hormone.
If you miss a dose, take it as soon as you remember on that same day. If you don't realize you missed the dose until the next day, skip the missed dose and continue with your regular schedule; never take two doses at once. If you miss more than two days in a row, you must contact your doctor immediately. You will likely need to temporarily increase your oral calcium and vitamin D intake to prevent your blood calcium from dropping too low. Keeping a backup supply of oral supplements is highly recommended for such situations.
Weight gain was not a commonly reported side effect in the clinical trials for Parathyroid Hormone. However, the medication affects your metabolism and mineral balance, which can sometimes lead to changes in energy levels or fluid retention. If you notice rapid or unexplained weight gain, it is more likely related to other factors or potentially a sign of kidney issues, which should be evaluated by your physician. It is always a good idea to monitor your weight and report significant changes to your healthcare team.
Parathyroid Hormone can interact with several other drugs, most notably Digoxin and certain diuretics (water pills). Because it raises blood calcium, it can make Digoxin more toxic to the heart. Thiazide diuretics can also cause calcium levels to become too high when combined with this hormone. You must provide your doctor with a complete list of all prescriptions, over-the-counter drugs, and herbal supplements you are taking. Your doctor will then monitor your blood levels more frequently to ensure no dangerous interactions occur.
As of 2026, Parathyroid Hormone (rhPTH 1-84) is a complex biologic medication and is not available in a standard 'generic' form. There may be biosimilar versions in development, but because it is a protein-based hormone produced in living cells, it is much more difficult to replicate than simple chemical drugs. Additionally, because the brand-name version (Natpara) is part of a restricted REMS safety program, any future biosimilars would also likely be subject to strict distribution controls. Most patients will continue to receive the brand-name version for the foreseeable future.
> Warning: Stop taking Parathyroid Hormone and call your doctor immediately if you experience any of these serious conditions:
Long-term use of Parathyroid Hormone requires monitoring for bone health and kidney function. Because the hormone stimulates bone turnover, there is a theoretical risk of changing bone mineral density over many years. Additionally, chronic fluctuations in calcium and phosphate can lead to 'ectopic calcification' (calcium deposits in soft tissues like the kidneys or brain) if not managed precisely.
In male and female rats, parathyroid hormone caused an increase in the incidence of osteosarcoma (a malignant bone tumor). The occurrence of osteosarcoma was dependent on the dose and the duration of treatment. Because the relevance of these rat findings to humans is unknown, Parathyroid Hormone should be prescribed only to patients with hypoparathyroidism who cannot be well-controlled on standard therapy and for whom the potential benefits outweigh the potential risk of osteosarcoma. Avoid use in patients who are at increased baseline risk for osteosarcoma, such as those with Paget’s disease of bone, open epiphyses (pediatric patients), or prior external beam or implant radiation therapy involving the skeleton.
Report any unusual symptoms or side effects to your healthcare provider immediately. Regular blood work is mandatory to ensure your safety while on this medication.
While taking Parathyroid Hormone, you will need frequent laboratory tests, including:
Parathyroid Hormone generally does not affect the ability to drive. However, if you experience symptoms of hypocalcemia (such as dizziness or muscle twitching) or hypercalcemia (such as confusion), you should avoid operating heavy machinery until your calcium levels are stabilized.
There is no direct chemical interaction between alcohol and Parathyroid Hormone. However, excessive alcohol consumption can interfere with calcium absorption and worsen dehydration, which increases the risk of kidney stones. It is best to limit alcohol intake to moderate levels.
NEVER stop taking Parathyroid Hormone abruptly. If you must stop the medication, your doctor will implement a 'taper-up' strategy for your oral calcium and vitamin D supplements. Without the hormone, your calcium levels will drop rapidly, often within 24 to 48 hours, which can lead to seizures or tetany.
> Important: Discuss all your medical conditions, especially any history of bone disease or radiation therapy, with your healthcare provider before starting Parathyroid Hormone.
Parathyroid Hormone treatment will naturally affect the results of several lab tests:
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking. Even 'natural' supplements can have profound effects on your mineral balance.
These conditions require a careful risk-benefit analysis by a specialist:
There is a potential for cross-sensitivity with other parathyroid hormone analogs like Teriparatide (Forteo) or Abaloparatide (Tymlos). If you have had a severe allergic reaction to those drugs, you should not use Parathyroid Hormone (rhPTH 1-84).
> Important: Your healthcare provider will evaluate your complete medical history, including any history of cancer or radiation, before prescribing Parathyroid Hormone.
Clinical studies of Parathyroid Hormone did not include enough subjects aged 65 and over to determine whether they respond differently than younger subjects. In general, elderly patients have a higher prevalence of decreased renal function and are more likely to be taking concurrent medications like Digoxin or diuretics. Therefore, dose titration should be slower, and monitoring of calcium and kidney function should be more frequent.
For patients with mild to moderate renal impairment (Creatinine Clearance 30 to 80 mL/min), no specific starting dose adjustment is needed. However, these patients are at a higher risk for 'calcium-phosphate product' elevation, which can lead to calcification of the kidneys (nephrocalcinosis). For patients with severe renal impairment or those on dialysis, the drug should be used with extreme caution, as the pharmacokinetics have not been fully studied in this group.
In patients with mild to moderate hepatic impairment, the peak concentration and total exposure to the drug are slightly lower, but not enough to require a dose adjustment. There is no data available for patients with severe hepatic impairment (Child-Pugh Class C). Since the liver is a site of peptide cleavage, these patients should be monitored closely if the drug is initiated.
> Important: Special populations require individualized medical assessment and frequent lab monitoring to ensure the safety of both the patient and, in the case of pregnancy, the developing fetus.
| Parameter | Value |
|---|---|
| Bioavailability | ~53% (Subcutaneous) |
| Protein Binding | Low (primarily circulates freely) |
| Half-life | ~3 hours (Terminal) |
| Tmax | 5 to 30 minutes |
| Metabolism | Hepatic and systemic proteolysis |
| Excretion | Minimal renal excretion of intact protein |
Parathyroid Hormone is the flagship member of the Parathyroid Hormone [EPC] class. It is distinct from 'bisphosphonates' (which inhibit bone breakdown) and 'calcimimetics' (which lower PTH). It is a true hormone replacement therapy, similar in concept to using insulin for diabetes or levothyroxine for hypothyroidism.