Peptides for Osteoporosis: Teriparatide, Abaloparatide, Calcitonin, and an Oral Bone Builder in Testing

Osteoporosis means bones have lost enough mass and inner structure that they break easily, often in the spine, hip, or wrist. Most drugs used to treat it are antiresorptive, meaning they slow the cells that break bone down. Bisphosphonate pills such as alendronate work this way, and so does denosumab (Prolia), a shot given every six months.

Two approved drugs work the other way. Teriparatide (sold as Forteo and as cheaper generic versions) and abaloparatide (Tymlos) are anabolic, meaning they help the body build new bone. Both are peptides, short chains of amino acids, and both are taken as a daily shot under the skin. They are usually saved for people at the highest risk of breaking a bone, and the order in which they are used turns out to matter.

Parathyroid hormone (PTH) helps control the amount of calcium in the blood, and its effect on bone depends on timing. The Bone Health and Osteoporosis Foundation (BHOF) explains in its 2022 clinician guide that constant high exposure to PTH breaks bone down, while a short daily dose stimulates bone formation. Teriparatide is a lab-made copy of the first 34 amino acids of human PTH. Abaloparatide copies the first 34 amino acids of a related hormone, PTH-related peptide, with some changes.

Both come in prefilled pens that last about a month. The Forteo dose is 20 micrograms once a day, and the Tymlos dose is 80 micrograms once a day, injected into the belly. Both labels tell patients to take their first doses where they can sit or lie down, because blood pressure can drop right after a shot and cause dizziness. Both also advise calcium and vitamin D supplements if a person does not get enough from food.

Forteo's main trial enrolled 1,637 postmenopausal women with osteoporosis, and 90% of them already had at least one spine fracture. Over a median of 19 months, new spine fractures seen on X-rays occurred in 5.0% of women on teriparatide and 14.3% of women on placebo, a 65% relative reduction. Fractures outside the spine fell from 5.5% to 2.6%.

In the ACTIVE trial, 824 postmenopausal women took Tymlos and 821 took placebo for 18 months. New spine fractures occurred in 0.6% of the Tymlos group and 4.2% of the placebo group, and fractures outside the spine in 2.7% and 4.7%. In December 2022, the FDA also approved Tymlos to increase bone density in men, based on the ATOM trial of 228 men. Spine bone density rose 8.5% on Tymlos and 1.2% on placebo after a year; the trial measured bone density, not fractures, as its main goal.

Teriparatide has also been tested against a standard pill. In the VERO trial, funded by Lilly, 1,360 women with severe osteoporosis and existing spine fractures took either daily teriparatide or weekly risedronate, a bisphosphonate, for two years. New spine fractures occurred in 5.4% of the teriparatide group and 12.0% of the risedronate group. The Forteo and Tymlos trials enrolled different women over different time periods, so their results cannot be compared to rank one drug above the other.

Doctors measure bone density with a DEXA scan (dual-energy X-ray absorptiometry), a low-dose X-ray of the hip and spine. The result is reported as a T-score, the number of standard deviations a person's bone density falls above or below the average for healthy young adults. A T-score of −2.5 or lower means osteoporosis. A score between −1.0 and −2.5 means low bone mass, often called osteopenia.

The BHOF guide recommends considering drug treatment for postmenopausal women and men age 50 and older who have a hip or spine fracture, a T-score of −2.5 or lower, or low bone mass plus a high 10-year fracture risk on the FRAX calculator (3% or more for a hip fracture, or 20% or more for a major osteoporotic fracture). It singles out people with recent fractures or very low bone density, such as a T-score below −3.0, as being at especially high risk, and it says drugs that only slow bone loss may not lower their risk enough.

For these patients, the sequence counts. The guide says an anabolic drug given after an antiresorptive drug has less effect on bone density than when the anabolic drug comes first, so starting with the bone builder is preferred. The gains also need protecting. The guide tells clinicians to start an antiresorptive drug after teriparatide or abaloparatide ends, because bone loss resumes once treatment stops.

A third bone-building drug, romosozumab (Evenity), is a monoclonal antibody rather than a peptide. It is limited to 12 monthly doses and carries a boxed warning about a possible increase in heart attack, stroke, and cardiovascular death.

Both peptides once carried a boxed warning, the FDA's strongest label warning, because high doses of teriparatide caused osteosarcoma, a bone cancer, in rats treated for most of their lives. Forteo was also limited to two years of use in a lifetime. Later studies linked pharmacy claims to cancer registries and found no increase in osteosarcoma among people who took teriparatide. According to a 2022 review in JBMR Plus by Lilly-affiliated authors, the FDA then removed Forteo's boxed warning in November 2020 and revised the two-year limit. The FDA removed Tymlos's boxed warning in December 2021.

The duration rules now differ. Forteo's label says use beyond two years should be considered only if a person remains at, or returns to, high fracture risk. Tymlos's label says the drug has not been studied beyond two years and that using it longer than two years in a lifetime is not recommended. Both labels still say to avoid these drugs in people with a higher baseline risk of osteosarcoma, such as those with Paget's disease of bone, past radiation therapy to the skeleton, or cancer that has spread to bone.

The FDA approved the first generic teriparatide pens, from Teva and Apotex, on November 16, 2023, and at least one more generic maker has been approved since. A separate version called Bonsity was approved in 2019 through a different pathway. No generic version of Tymlos has been approved.

Generics lowered the price without making it small. The National Average Drug Acquisition Cost (NADAC), a federal survey of what U.S. retail pharmacies pay for drugs, listed generic teriparatide at about $480 per milliliter as of September 30, 2026. That works out to roughly $1,075 for one 28-day pen. Brand-name Forteo was listed at about $1,841 per milliliter, or roughly $4,124 per pen. These are pharmacy purchase costs, not what a patient pays at the counter, which depends on insurance and discount programs. NADAC did not list Tymlos.

Calcitonin is a hormone made by the thyroid gland, and the drug is a lab-made copy of the salmon version. It slows bone breakdown rather than building bone. The BHOF guide says calcitonin nasal spray reduces spine fractures by about 30% in people who have already had one but does not reduce fractures elsewhere. The current U.S. label for Miacalcin injection allows it for postmenopausal osteoporosis only when other treatments are not suitable and states that fracture reduction has not been shown.

Cancer questions pushed calcitonin further back. In July 2012, the European Medicines Agency told doctors to stop prescribing calcitonin nasal spray for osteoporosis after a review found cancer rates 0.7% to 2.4% higher with calcitonin than with placebo. In March 2013, two FDA advisory committees voted 12 to 9 that the benefits of the nasal spray for osteoporosis did not outweigh its risks. The FDA kept calcitonin on the market. Its label now cites a meta-analysis of 21 trials in which cancers occurred in 4.1% of people on calcitonin and 2.9% on placebo, and tells doctors to check periodically whether treatment is still needed.

Like most peptide drugs, teriparatide must be injected, because a peptide swallowed as a pill is mostly broken down before it reaches the blood. Entera Bio is trying to change that with EB613, an oral tablet of the same PTH(1-34) peptide. In August 2026, the company said the FDA had accepted its plan for a single Phase 3 trial in about 750 postmenopausal women, with the change in total hip bone density at 12 months as the main measure. Entera raised about $275 million in July 2026 to pay for the trial, plans to start it in late 2026, and expects results in the second half of 2028. The trial will measure bone density rather than fractures, and the pill is not approved.

People taking GLP-1 drugs for weight loss often ask what the drugs do to bone. Our review of the fracture data covers a Stanford-led analysis presented at ENDO 2026 that linked semaglutide to a 15% lower fracture risk than other anti-obesity medicines in adults with type 2 diabetes, while noting that fast weight loss also removes some lean tissue. GLP-1 drugs are not approved to treat osteoporosis.

BPC-157, a peptide sold online with claims that it speeds healing, rests on much thinner evidence. A 2025 systematic review in HSS Journal found 36 studies on its use for muscle, tendon, ligament, and bone injuries. Thirty-five were in animals or cells, and the only human study was a small retrospective report on knee pain. The authors found no clinical safety data, and BPC-157 is not approved by the FDA. None of the studies tested it for osteoporosis or fracture prevention in people.

If you have osteoporosis or a fracture from a minor fall, these questions can help you understand where a peptide fits:

• What is my T-score, and what is my 10-year fracture risk on FRAX?
• Am I at very high risk, and if so, should I start with a bone-building drug before a bisphosphonate or denosumab?
• If I take teriparatide or abaloparatide, which drug will I take afterward to keep the bone I gain?
• Does my plan cover generic teriparatide, Tymlos, or both, and what will I pay each month?
• Do I have a condition, such as Paget's disease or past radiation to bone, that rules these drugs out?
• Am I getting enough calcium and vitamin D from food, or do I need supplements?