PTH and PTHrP Peptide Hormones: Dual Roles in Bone Formation and Breakdown | Research

The takeaway

Review of how parathyroid hormone (PTH) and PTH-related protein (PTHrP) share a common receptor but exert complex, sometimes opposing effects on bone through their amino-terminal peptide domains — informing osteoporosis drug design.

Same receptor, opposite effects
PTH builds bone when given intermittently but breaks it down when continuous — dosing pattern completely reverses the peptide hormone's bone effect

What the researchers found

PTH and PTHrP share amino-terminal domain identity and PTH1R receptor activation but have distinct physiological and pharmacological roles in bone. Intermittent PTH builds bone (anabolic) while continuous PTH breaks it down (catabolic). Genetic models clarify mechanism distinctions.

Why it matters

Osteoporosis affects 200+ million people. Understanding how related peptide hormones build vs break bone enables design of better anabolic bone drugs — exemplified by teriparatide (PTH fragment) and abaloparatide (PTHrP-based).

The numbers in context

PTH1R shared receptor; cAMP-PKA pathway; teriparatide (PTH) and abaloparatide (PTHrP); intermittent = anabolic, continuous = catabolic

How the study worked

Narrative review of PTH and PTHrP bone biology using genetic model data to distinguish their physiological and pharmacological roles through PTH1R signaling.

Who was studied

N/A (review of human clinical, mouse genetic, and pharmacological data)

What this study cannot tell us

Review based heavily on genetic models that may not fully replicate human bone physiology. PTH1R signaling complexity not fully resolved. Clinical implications of some genetic findings unclear.

How to read the evidence

Not applicable (review). Based on genetic models and established clinical pharmacology of approved drugs.

When this study was published

Published 2021. PTH-based osteoporosis drugs (teriparatide, abaloparatide) are established treatments.

The bigger picture

Understanding the nuanced biology of closely related peptide hormones is essential for drug design. The PTH/PTHrP story shows how dosing pattern (intermittent vs continuous) can flip a peptide's effect from beneficial to harmful — a principle applicable to other peptide drugs.

Questions still open

Can next-generation PTH/PTHrP analogs provide even better bone building?
Why does intermittent vs continuous PTH have opposite bone effects?
Could oral PTH peptide analogs replace injectable teriparatide?

Common questions

How do PTH drugs build bone?

When PTH is given as a daily injection (intermittent), it stimulates bone-forming cells (osteoblasts) more than bone-breaking cells. This net effect builds new bone. Continuous PTH exposure has the opposite effect, which is why daily injections — not continuous infusion — are used.

What is the difference between teriparatide and abaloparatide?

Teriparatide (Forteo) is a fragment of human PTH. Abaloparatide (Tymlos) is based on PTHrP. Both build bone through the same receptor but with slightly different signaling. Abaloparatide may cause less calcium elevation. Both are daily injectable osteoporosis treatments.

Read the original research

Physiological and Pharmacological Roles of PTH and PTHrP in Bone Using Their Shared Receptor, PTH1R.

Endocrine reviews, 42(4), 383-406

View on PubMed ↗Publisher’s paper ↗

Citation

Martin, T John; Sims, Natalie A; Seeman, Ego. (2021). Physiological and Pharmacological Roles of PTH and PTHrP in Bone Using Their Shared Receptor, PTH1R.. Endocrine reviews, 42(4), 383-406. https://doi.org/10.1210/endrev/bnab005