teriparatide
Forteo (teriparatide) is a parathyroid hormone analog from Eli Lilly. Given as a daily injection, it stimulates new bone formation and is used to treat osteoporosis in people at high risk of fracture, including postmenopausal women, men with primary osteoporosis, and patients on long-term glucocorticoids.
This page is based on FDA prescribing information and the EMA medicine record for teriparatide; the mechanism is explained in plain language, and analogies are used only where they stay accurate.
How it works
Explains what the medicine does in the body, not dosing, side effects, or safety.
An analogy
Bone is constantly being remodeled — old bone is removed and new bone is built. Continuous exposure to parathyroid hormone tells the body to break bone down, but short daily bursts do the opposite: they wake up the bone builders and tell them to lay down fresh, strong bone. Teriparatide is that short daily burst, delivered as an injection.
In simple terms
Teriparatide is a small piece of human parathyroid hormone, the body's own signal for bone remodeling. When given as a once-daily injection, it acts in short bursts that stimulate osteoblasts — the cells that build new bone — more than they activate osteoclasts, the cells that break bone down. The result is thicker, stronger bone and fewer fractures. It is used in people whose bones are fragile from menopause, aging, or long-term steroid use.
In depth
Teriparatide is recombinant human parathyroid hormone (1-34), the biologically active N-terminal fragment of endogenous 84-amino-acid PTH. It binds the PTH1 receptor (PTH1R) on osteoblasts and osteocytes. Unlike continuous PTH elevation, which favors bone resorption, intermittent low-dose exposure preferentially activates adenylyl cyclase–cAMP–PKA signaling, upregulating Runx2 and osterix transcription factors that drive osteoblast differentiation and activity. This increases trabecular bone formation, improves microarchitecture, and raises bone mineral density. Intermittent PTH also transiently raises RANKL, coupling some resorptive activity, but the net balance is anabolic.
See it in motion
A schematic animation of the mechanism — simplified for clarity, not drawn to scale.
Bone is constantly being remodeled — old bone is removed and new bone is built.
- Teriparatide is a small piece of human parathyroid hormone, the body's own signal for bone remodeling.
- Continuous exposure to parathyroid hormone tells the body to break bone down, but short daily bursts do the opposite: they wake up the bone builders and tell them to lay down fresh, strong bone.
- When given as a once-daily injection, it acts in short bursts that stimulate osteoblasts — the cells that build new bone — more than they activate osteoclasts, the cells that break bone down.
- The result is thicker, stronger bone and fewer fractures.
Target: Parathyroid hormone receptor (PTH1R)
A G-protein-coupled receptor on bone-building cells; when activated intermittently by low-dose PTH it shifts the balance toward new bone formation rather than bone breakdown.
Approved uses
Approved uses differ by country and change over time. Always follow your local prescribing information.
Approved uses in United States
FDA- Treatment of postmenopausal women with osteoporosis at high risk for fracture (defined as having a history of osteoporotic fracture or multiple risk factors for fracture) or who have failed or are intolerant to other available osteoporosis therapy
- To increase bone mass in men with primary or hypogonadal osteoporosis at high risk for fracture or who have failed or are intolerant to other available osteoporosis therapy
- Treatment of men and women with osteoporosis associated with sustained systemic glucocorticoid therapy at high risk for fracture or who have failed or are intolerant to other available osteoporosis therapy
Approved uses in European Union
EMA- Treatment of osteoporosis in postmenopausal women and in men at increased risk of fracture
- Treatment of osteoporosis associated with sustained systemic glucocorticoid therapy in women and men at increased risk for fracture
Official sources
The statements on this page trace back to these records.
- U.S. Food and Drug Administration: teriparatide prescribing information
U.S. Food and Drug Administration
- Forsteo (teriparatide) — Summary of product characteristics and package leaflet, English version
European Medicines Agency
- Emc SmPC: Teriparatide (UK licensed product)
Medicines and Healthcare products Regulatory Agency (EMC)
This page explains how the medicine works — it isn’t the patient leaflet. For anything that applies to you, read the leaflet that came with your medicine or ask your pharmacist.
MedUnfold provides educational content and is not medical advice. Always follow your local prescribing information and healthcare professional.