Teriparatide
Teriparatide (Forteo)
Teriparatide is a recombinant human parathyroid hormone analogue (rhPTH 1-34) representing the biologically active N-terminal fragment of endogenous PTH. It is FDA-approved for treatment of osteoporosis in postmenopausal women, men with primary or hypogonadal osteoporosis, and patients with glucocorticoid-induced osteoporosis at high fracture risk. It is the first anabolic bone-building agent approved for osteoporosis, distinct from antiresorptive therapies.
Mechanism of Action
Teriparatide binds to the PTH/PTHrP receptor (PTH1R) on osteoblasts and osteoblast precursors, activating adenylyl cyclase via Gs-protein coupling to increase intracellular cAMP. Intermittent administration preferentially stimulates osteoblast differentiation, proliferation, and survival while suppressing osteoblast apoptosis, resulting in net bone formation and increased bone mineral density at both trabecular and cortical sites. This anabolic effect contrasts with the catabolic effect of continuous PTH exposure, which favors osteoclast activation and bone resorption.
Evidence by Health Goal(16 goals)
Dosing Protocols
Same time each day; patient may sit for first several doses to mitigate orthostatic hypotension risk
Cycle: Maximum cumulative duration of 24 months (lifetime limit) per FDA labeling
Administered as subcutaneous injection into thigh or abdomen using a prefilled pen device. The 24-month lifetime limit applies due to osteosarcoma risk observed in rat studies at suprapharmacological doses. Following discontinuation, antiresorptive therapy (e.g., bisphosphonate) is recommended to preserve bone gains.
Safety & Side Effects
Teriparatide carries an FDA boxed warning regarding osteosarcoma risk based on dose- and duration-dependent findings in rat studies, though causality in humans has not been established across post-marketing surveillance. It is contraindicated in patients with Paget's disease, prior skeletal radiation, hypercalcemia, metabolic bone diseases other than osteoporosis, and in pediatric patients; it is a prescription-only medication in all jurisdictions and should only be used under physician supervision.
Possible Side Effects
- !Nausea (most common, affects approximately 8-14% of patients)
- !Orthostatic hypotension with dizziness or lightheadedness, particularly after initial doses
- !Leg cramps and musculoskeletal discomfort
- !Hypercalcemia (transient, typically mild; peaks 4-6 hours post-injection)
- !Hypercalciuria with risk of nephrolithiasis in predisposed individuals
- !Injection site reactions including erythema, pain, and bruising
- !Headache and fatigue
- !Elevated serum uric acid levels (asymptomatic hyperuricemia)
Interactions
- -Concurrent digoxin use carries increased risk of digoxin toxicity due to teriparatide-induced transient hypercalcemia, which sensitizes the myocardium to digitalis
- -Loop diuretics (e.g., furosemide) may exacerbate hypercalciuria, increasing nephrolithiasis risk
- -Thiazide diuretics may potentiate hypercalcemia when combined with teriparatide-induced calcium elevation
- -Active vitamin D analogues (e.g., calcitriol) and high-dose calcium supplementation increase hypercalcemia risk and require monitoring
- -Antihypertensive medications: additive hypotensive effect possible due to teriparatide-induced orthostatic hypotension
Cost & Where to Buy
Brand-name Forteo has a list price exceeding $3,000/month in the US without insurance; generic teriparatide (available since 2019, e.g., Bonsity, Tlando equivalents) and manufacturer copay assistance programs can reduce out-of-pocket costs significantly. International pricing is substantially lower. Research-grade peptide vendors offer teriparatide at far lower cost but without pharmaceutical-grade quality control or regulatory approval for human use.
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