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# Parathyroid hormone (PTH) analogues

Daily injections of a PTH fragment that build new bone. Anabolic, unlike the drugs that only slow bone loss.

Updated Nov 1, 2026

## What they are

Peptides that act on the PTH type 1 receptor. Given once a day under the skin, in short pulses, they stimulate osteoblasts more than osteoclasts, so bone mass and strength increase. They are used for severe osteoporosis at high fracture risk, usually for a limited time and then followed by an antiresorptive.

## Mechanism of action

Continuous high PTH, as in hyperparathyroidism, mainly drives resorption. Brief daily peaks instead activate the PTH1 receptor on osteoblasts and their precursors (a G-protein–coupled receptor that raises cAMP), increase their number and activity and reduce their death, and favour formation over resorption. New bone is laid down on trabecular and cortical surfaces.

Target: PTH/PTHrP type 1 receptor (PTH1R), a G-protein–coupled receptor on osteoblasts

## Key points

- The effect depends on the pattern: intermittent PTH is anabolic, continuous PTH destroys bone.
- Avoided when the baseline risk of osteosarcoma is higher: Paget disease, open epiphyses, previous skeletal radiation, bone cancer or metastases.
- Avoided in hypercalcaemic disorders such as primary hyperparathyroidism; it can raise calcium transiently.
- The first doses can cause orthostatic hypotension, so they are given sitting or lying down.
- After the course, an antiresorptive keeps the bone gained.

## Drugs in this class

- [**Teriparatide** The first 34 amino acids of human parathyroid hormone, injected once a day to build new bone in severe osteoporosis. PTH/PTHrP type 1 receptor (PTH1R), a G-protein–coupled receptor](https://durgical.com/en/pharmacology/teriparatide/)
- [**Abaloparatide** A daily injection of a PTH-related peptide analogue that builds new bone. Used in osteoporosis at high fracture risk. Parathyroid hormone/PTHrP receptor type 1 (PTH1R)](https://durgical.com/en/pharmacology/abaloparatide/)

## Others in the class

- Abaloparatide

## Test yourself

Think of the answer, then tap the question to see it.

## Why does once-daily teriparatide build bone while hyperparathyroidism destroys it?

Short daily peaks of PTH stimulate osteoblasts more than osteoclasts; continuous high PTH mainly drives resorption.

## Which conditions are avoided with PTH analogues because of osteosarcoma risk?

Paget disease of bone, open epiphyses (children), previous radiation to the skeleton, and bone cancer or metastases.

## What is usually given after a course of a PTH analogue, and why?

An antiresorptive such as a bisphosphonate or denosumab, so the new bone is not lost once the anabolic drug stops.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Teriparatide Injection: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a603018.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [DailyMed - TERIPARATIDE injection](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=d38b470a-2e62-487b-b3e7-134d3d1958b5) (DailyMed (U.S. National Library of Medicine), 2026).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/classes/parathyroid-hormone-analogues/