science

Recombinant human parathyroid hormone

Recombinant human parathyroid hormone is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Recombinant human parathyroid hormone rather than just read about it. In short: Recombinant human parathyroid hormone is an artificially manufactured form of the parathyroid hormone used to help treat hypoparathyroidism (under-active parathyroid glands) and osteoporosis. Recombinant human parathyroid hormone (Preotact) received market authorization in the European Union in April 2006 to treat osteoporosis in postmenopausal women at high risk of fractures.

Key takeaways

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Reference excerpt

Recombinant human parathyroid hormone is an artificially manufactured form of the parathyroid hormone used to help treat hypoparathyroidism (under-active parathyroid glands) and osteoporosis. Recombinant human parathyroid hormone (Preotact) received market authorization in the European Union in April 2006 to treat osteoporosis in postmenopausal women at high risk of fractures. Preotact marketing authorisation was later voluntarily withdrawn in 2014 by the holder NPS Pharma. FDA approval (as Preos) was not granted in the US for the same indication due to hypercalcemia and injection device issues. Recombinant human parathyroid hormone (Natpara) was approved for medical use in the United States in January 2015, and received (as Natpar) conditional market authorization in the European Union in February 2017 as orphan drug. On 2019 Natpara was recalled in the US due to rubber particle issues emerging from daily use of the cartridge. Takeda announced in 2022 its decision to stop manufacturing Natpara/Natpar globally at the end of 2024.

Medical uses Recombinant human parathyroid hormone (Natpara) is indicated as an adjunct to calcium and vitamin D to control hypocalcemia in people with hypoparathyroidism. Recombinant human parathyroid hormone (Natpar) is indicated as adjunctive treatment of adults with chronic hypoparathyroidism who cannot be adequately controlled with standard therapy alone. Recombinant human parathyroid hormone (Preotact) is indicated for the treatment of osteoporosis in postmenopausal women at high risk of fractures, but the marketing authorization has been withdrawn at the manufacturer's request.

Contraindications

Parathyroid hormone treatment should not be initiated in patients:

with hypersensitivity to PTH or excipients who have received radiation therapy to the skeleton with pre-existing hypercalcemia and other disturbances in the metabolism of phosphate or calcium with metabolic bone diseases other than primary osteoporosis (including hyperparathyroidism and Paget's disease) with unexplained elevations of bone-specific alkaline phosphatase with severe chronic kidney disease with severe liver impairment

Adverse effects The most common side effects include too high or too low blood calcium levels, which can lead to headache, diarrhea, vomiting, paraesthesia (unusual sensations like pins and needles), hypoaesthesia (reduced sense of touch), and high calcium levels in the urine. In the US, the FDA label for parathyroid hormone contains a black box warning for osteosarcoma (a malignant bone tumor).

Interactions

Parathyroid hormone is a natural peptide that is not metabolised in the liver. It is not protein bound and has a low volume of distribution, therefore no specific drug-drug interactions are suspected. From the knowledge of the mechanism of action, combined use of Preotact and cardiac glycosides may predispose patients to digitalis toxicity if hypercalcemia develops.

Undesirable effects

Hypercalcemia and/or hypercalciuria reflect the known pharmacodynamic actions of parathyroid hormone in the gastrointestinal tract, the kidney and the skeleton, and is therefore an expected undesirable effect. Nausea is another commonly reported adverse reaction to the use of parathyroid hormone.

Pharmacodynamic properties

Mechanism of action

Preotact contains recombinant human parathyroid hormone which is identical to the full-length native 84-amino acid polypeptide. Physiological actions of parathyroid hormone include stimulation of bone formation by direct effects on bone forming cells (osteoblasts) indirectly increasing the intestinal absorption of calcium and increasing the tubular reabsorption of calcium and excretion of phosphate by the kidney.

Pharmacodynamic effects

The skeletal effects of parathyroid hormone depend upon the pattern of systemic exposure. Transient elevations in parathyroid hormone levels after subcutaneous injection of Preotact stimulates new bone formation on trabecular and cortical bone surfaces by preferential stimulation of osteoblastic activity over osteoclastic activity.

Effects on serum calcium concentrations

Parathyroid hormone is the principal regulator of serum calcium hemostasis. In response to subcutaneous doses of Preotact (100 micrograms), serum total calcium levels increase gradually and reach peak concentration at approximately 6 to 8 hours after dosing. In general, serum calcium levels return to normal within 24 hours.

Clinical efficacy

In an 18-month double-blind, placebo controlled study, the effects of Preotact on the fracture incidence in 2532 women with postmenopausal osteoporosis was studied. Approximately 19% of patients had a prevalent vertebral fracture at baseline and the mean lumbar T-score of -3.0 in both active and placebo arm. Compared to the placebo group, there was a 61% relative risk reduction of a new vertebral fracture at month 18 for the women in the Preotact group. To prevent one or more new vertebral fractures, 48 women had to be treated for a median of 18 months for the total population. For patients who were already fractured, the number needed to treat was 21.

Effect on bone mineral density

In the same study mentioned above, Preotact increased bone mineral density in the lumbar spine after 18 months treatment by 6.5% compared with a reduction by 0.3% in the placebo group. The difference was statistically significant. The increase of bone mineral density in the hip was also statistically significant compared to placebo, but only around 1.0% at study endpoint. Continued treatment up to 24 months lead to a continued increase in bone mineral density.

Pharmacokinetics

Absorption

Subcutaneous administration of parathyroid hormone into the abdomen produces a rapid increase in plasma parathyroid hormone levels which reach peak at 1 to 2 hours after dosing. The mean half-life is approximately 1.5 hours. The absolute bioavailability of 100 micrograms of Preotact after subcutaneous administration in the abdomen is 55%.

Distribution

The volume of distribution at steady-state following intravenous administration is approximately 5.4 liters. Intersubject variability is about 40%.

Biotransformation

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Illustrations

Worked examples

Example 1 — a first encounter with Recombinant human parathyroid hormone

Start with the simplest possible case. Write down what Recombinant human parathyroid hormone claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Recombinant human parathyroid hormone before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Recombinant human parathyroid hormone ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Recombinant human parathyroid hormone

In research: Recombinant human parathyroid hormone appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Recombinant human parathyroid hormone in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Recombinant human parathyroid hormone is common in secondary-school and first-year university syllabi. It links to neighbouring topics Drugs acting on the musculoskeletal system, Drugs developed by Takeda Pharmaceutical Company, Hormones of calcium metabolism, so understanding it makes those chapters shorter.
In everyday life: Look for Recombinant human parathyroid hormone outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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Frequently asked questions

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Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

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