Anabolic Therapy for Osteoporosis: Drugs, Safety, Sequencing

Anabolic therapy for osteoporosis uses drugs that build new bone rather than only slowing its breakdown. Three are approved in the US: teriparatide (Forteo), abaloparatide (Tymlos), and romosozumab (Evenity). They are the preferred first-line treatment for patients at very high fracture risk, given for a fixed course of 12 to 24 months and always followed straight away by an antiresorptive such as denosumab or a bisphosphonate to lock in the gain.

Bisphosphonates and denosumab reduce osteoclast activity; anabolic agents stimulate osteoblasts and produce larger, faster increases in bone mineral density (BMD). In their pivotal trials they reduced new vertebral fractures by roughly two-thirds or more versus placebo, and head-to-head trials against oral antiresorptives favored the anabolic arm. Major guidelines, including those of the AACE and the Endocrine Society, now recommend an anabolic-first, “build then maintain” sequence for very-high-risk patients.

This guide covers patient selection, the three agents side by side, efficacy by fracture site, safety and contraindications per drug, sequencing (including the problem of switching from denosumab), combination therapy, monitoring, and payer criteria.

Who Qualifies for Anabolic Therapy?

Anabolic agents are reserved for patients at very high fracture risk. Definitions vary slightly between guidelines, but the AACE criteria are widely used. A patient is very high risk if they have any of the following:

• A fracture within the past 12 months (imminent fracture risk)
• A fracture while on approved osteoporosis therapy
• Multiple fractures
• A fracture while taking drugs that harm bone, such as long-term glucocorticoids
• A very low T-score, below −3.0 at the spine or hip
• A high risk of falls or a history of injurious falls
• A very high FRAX 10-year probability: major osteoporotic fracture above 30% or hip fracture above 4.5%

Patients who are high risk but not very high risk, for example a T-score of −2.6 with no fracture, can reasonably start on an antiresorptive. Clinical judgment still matters: a recent vertebral fracture in a patient with an otherwise modest T-score often justifies anabolic treatment. Vertebral fractures can also be the first sign of myeloma or another secondary cause of bone loss, so baseline laboratory work, including a comprehensive anemia panel, serum protein electrophoresis where indicated, calcium, 25-hydroxyvitamin D, renal function, PTH, and alkaline phosphatase, should be complete before starting.

Comparing the Three Anabolic Agents

Efficacy: Fractures and BMD by Site

Each agent was tested in a different population with different comparators, so cross-trial comparisons are indirect. The headline results from the pivotal trials are:

Romosozumab produces the fastest and largest BMD gains, especially at the hip, because it combines increased formation with reduced resorption. The PTH-pathway agents give steady spine gains, with hip BMD responding more slowly and sometimes dipping transiently in the first months as cortical remodeling increases.

Is Abaloparatide Better Than Teriparatide for the Hip?

In ACTIVE, abaloparatide produced greater total hip and femoral neck BMD gains than open-label teriparatide, and non-vertebral fracture rates were numerically lower. ACTIVE was not designed or powered to compare hip fracture rates between the two, so there is no evidence that abaloparatide prevents more hip fractures. When hip BMD is the main concern, abaloparatide or romosozumab is a reasonable choice, but the fracture-level difference remains unproven.

Safety and Contraindications by Agent

The Osteosarcoma Warning: History and Current Status

Both PTH-pathway drugs originally carried a boxed warning because rats given lifelong, high-dose teriparatide or abaloparatide developed osteosarcoma. The rat exposures were much higher and longer, relative to lifespan, than human treatment, and rat bone differs from human bone in how it responds to continuous remodeling stimulation.

Post-marketing surveillance programs for teriparatide, running for about 15 years, found no signal of increased osteosarcoma in treated patients. On that basis the FDA removed the teriparatide boxed warning in 2020 and relaxed the strict two-year lifetime limit: treatment beyond two years can be considered if a patient remains at or returns to high fracture risk. Abaloparatide’s boxed warning was removed in 2021, though its label still limits cumulative use to two years. The practical contraindications remain: avoid both drugs in patients with a raised baseline osteosarcoma risk (Paget’s disease, unexplained high alkaline phosphatase, prior skeletal radiation, open epiphyses, or skeletal malignancy).

Romosozumab: Cardiovascular Risk and Other Precautions

In ARCH, serious cardiovascular events, a composite of cardiac ischemic events and cerebrovascular events, occurred more often with romosozumab than with alendronate in the first year. FRAME, which used placebo, did not show the same imbalance, and it remains unclear whether romosozumab increases risk or alendronate is mildly protective. The label carries a boxed warning: do not start romosozumab within a year of MI or stroke, weigh the risk in patients with other cardiovascular risk factors, and stop it if MI or stroke occurs during treatment.

Romosozumab can cause hypocalcemia, particularly in patients with severe renal impairment or on dialysis. Correct hypocalcemia and replete vitamin D before the first dose, keep patients on adequate calcium and vitamin D throughout, and monitor serum calcium in those with advanced chronic kidney disease. Dental review before treatment is sensible, as with any potent bone agent, given the rare risk of osteonecrosis of the jaw.

Sequencing: Why the Order Matters

The gains from anabolic therapy are lost if it is not followed by an antiresorptive. After stopping teriparatide or abaloparatide without follow-on therapy, BMD falls over the following year or two; after romosozumab, gains are also lost without consolidation. Going straight from the anabolic course to an antiresorptive preserves and often extends the gain.

Anabolic First, Then Antiresorptive

• Months 0–12 or 0–24: romosozumab for 12 months, or teriparatide or abaloparatide for up to 24 months.
• Immediately after: denosumab (largest further BMD gains) or a bisphosphonate (oral alendronate or IV zoledronic acid). Leave no gap.
• Monitoring: DXA at baseline, at the switch, and one to two years into the antiresorptive phase.

In ARCH, patients who started on romosozumab then switched to alendronate kept a fracture advantage over those treated with alendronate throughout, which supports front-loading the anabolic agent.

Is Anabolic Therapy Safe After Denosumab?

This is one of the trickiest sequences. Stopping denosumab without a follow-on antiresorptive triggers a rebound surge in bone turnover. BMD gains are lost within about a year, and some patients suffer multiple spontaneous vertebral fractures in the months after the last missed dose. Denosumab should never simply be stopped.

Switching from denosumab to teriparatide makes this worse at first: in the DATA-Switch study, patients moved from denosumab to teriparatide lost BMD at the hip and spine over the following year, while those who went from teriparatide to denosumab kept gaining. Starting romosozumab after denosumab gives only modest additional spine gains and roughly maintains hip BMD, but it has an antiresorptive component, so it is generally preferred over a PTH analog when an anabolic is needed after denosumab. If a PTH analog is chosen, some clinicians overlap it with denosumab for a period, or give zoledronic acid, to blunt the rebound. There is no consensus protocol; this situation merits specialist input.

After Bisphosphonates

Patients who fracture on bisphosphonates are strong candidates for anabolic therapy, and no washout is needed. The BMD response to teriparatide is somewhat blunted after long-term bisphosphonate use, and hip BMD can dip transiently in the first months. Romosozumab’s response is less affected, which makes it attractive for bisphosphonate-experienced patients with low hip BMD or hip-predominant disease, provided there is no cardiovascular contraindication. Abaloparatide is a reasonable alternative when romosozumab is unsuitable.

Can Anabolic and Antiresorptive Drugs Be Combined?

The DATA study gave teriparatide and denosumab together for up to two years and found greater BMD gains at the spine and hip than either drug alone. The combination blocks the resorption that teriparatide would otherwise stimulate while preserving formation. However, no trial has shown fewer fractures with combination therapy, it doubles cost and injection burden, and payers rarely cover it.

Combining teriparatide with a bisphosphonate has been less promising, as alendronate blunted teriparatide’s effect in early studies. Combination therapy is therefore not standard practice; it may be considered in selected patients at exceptionally high risk, usually in specialist centers.

Monitoring Response With Bone Turnover Markers

Bone turnover markers are underused but helpful for confirming that the drug is working, well before DXA can show a change.

• P1NP (procollagen type I N-propeptide): the preferred formation marker. It should rise clearly within one to three months of starting teriparatide or abaloparatide. With romosozumab, P1NP rises early and then falls back toward baseline over the year.
• CTX (C-terminal telopeptide): a resorption marker. It rises with teriparatide and abaloparatide as remodeling increases, and falls with romosozumab.

If P1NP does not rise after three months of a PTH analog, check adherence, injection technique, and pen storage before concluding the drug has failed. Draw CTX fasting in the morning, since it varies with food and time of day.

Romosozumab’s formation effect attenuates over the first year, one reason the course is limited to 12 doses; further dosing adds little. Teriparatide and abaloparatide keep stimulating formation through the second year, though incremental gains are smaller.

Choosing Between the Three Agents

No trial has compared all three drugs for fracture outcomes, so the choice rests on the patient’s fracture pattern, cardiovascular history, renal function, sex, prior treatment, and ability to manage daily injections.

Before Starting: A Practical Checklist

• Confirm the diagnosis and risk category: recent DXA, vertebral imaging if height loss or back pain, FRAX, and a fracture history with dates.
• Exclude secondary causes: CBC, calcium, phosphate, albumin, creatinine and eGFR, alkaline phosphatase, 25-hydroxyvitamin D, PTH, thyroid function, and in men testosterone. Add serum protein electrophoresis and free light chains when myeloma is possible, as it often is with vertebral fractures and anemia.
• Replete vitamin D and calcium: correct deficiency before the first dose, especially before romosozumab.
• Check contraindications: Paget’s disease, unexplained high alkaline phosphatase, prior skeletal radiation, bone metastases, hypercalcemia, and for romosozumab, recent MI or stroke.
• Dental review: complete invasive dental work before starting a potent bone agent where possible, particularly if denosumab or a bisphosphonate will follow.
• Plan the follow-on therapy: decide and document the antiresorptive before the anabolic course starts, so the switch is not delayed.

Special Populations

Glucocorticoid-Induced Osteoporosis

Glucocorticoids suppress osteoblasts, so an anabolic mechanism is a logical fit. Teriparatide is approved for glucocorticoid-induced osteoporosis and, in a head-to-head trial against alendronate in patients on long-term glucocorticoids, produced greater spine BMD gains and fewer new vertebral fractures. Patients on high-dose or long-term steroids who fracture qualify as very high risk.

Chronic Kidney Disease

Mild to moderate CKD does not preclude anabolic therapy. In severe CKD (eGFR under 30) and dialysis, low bone turnover and hyperparathyroid bone disease can mimic osteoporosis, and treating the wrong condition can cause harm. These patients need specialist assessment, sometimes including bone biopsy, before any osteoporosis drug. If romosozumab is used, monitor calcium closely.

Premenopausal Women and Younger Adults

Anabolic agents are occasionally used in younger adults with severe osteoporosis, for example pregnancy- and lactation-associated osteoporosis or glucocorticoid-induced disease. PTH analogs must not be used while the epiphyses are open. Romosozumab and PTH analogs are not recommended in pregnancy, and contraception should be discussed with women of childbearing potential.

Patient Counseling and Adherence

Adherence to daily injections falls off over two years, and missed doses reduce benefit. What I cover with every patient:

• Injection technique: teach it in clinic, rotate sites between the thigh and abdomen, and check the pen at the first follow-up.
• First doses: take the first few injections sitting or lying down, and stand up slowly, because PTH analogs can cause dizziness and a fast heartbeat.
• Timing: injecting at bedtime helps some patients who get dizzy or nauseated.
• Storage: keep teriparatide refrigerated; abaloparatide goes in the fridge before first use and can stay at room temperature afterward within its use period.
• Symptoms to report: chest pain, stroke symptoms, or muscle cramps and tingling (possible hypocalcemia) with romosozumab; persistent nausea, weakness, or confusion (possible hypercalcemia) with PTH analogs.
• The plan after the course: patients should know from day one that an antiresorptive follows, so they don’t assume treatment is finished.

Fall prevention, adequate protein, calcium, vitamin D, and resistance and balance exercise remain part of every treatment plan; no drug compensates for repeated falls.

Reimbursement and Payer Criteria

Access often depends less on evidence than on payer rules. In the US, most commercial and Medicare Part D plans require prior authorization and often step therapy: documented very high fracture risk, and frequently a fracture on or intolerance of a bisphosphonate before an anabolic is covered. Document the qualifying fracture, the T-score, FRAX, prior therapies with dates, and any contraindication to oral bisphosphonates. Romosozumab is typically covered as a clinician-administered drug, which can change the benefit pathway compared with self-injected pens.

Other countries apply their own rules. Australia’s PBS, for example, has historically restricted subsidized teriparatide to patients with a very low T-score (−3.0 or lower) and at least two minimal-trauma fractures, including a new fracture despite antiresorptive therapy. Criteria change, so check the current local listing before prescribing.

Anabolic Therapy in Men

Male osteoporosis is underdiagnosed and undertreated. Teriparatide is approved for men with primary or hypogonadal osteoporosis and for glucocorticoid-induced osteoporosis, and abaloparatide gained approval for men at high fracture risk in 2022. Romosozumab is approved only for postmenopausal women in the US. Secondary causes, especially hypogonadism, glucocorticoid use, alcohol, and myeloma, should be excluded first.

Key Takeaways

• Anabolic-first therapy is guideline-recommended for very-high-risk patients; don’t default to a bisphosphonate.
• Romosozumab gives the largest, fastest BMD gains, especially at the hip, but is contraindicated within a year of MI or stroke and can cause hypocalcemia in severe CKD.
• Teriparatide and abaloparatide no longer carry an osteosarcoma boxed warning; avoid them in Paget’s disease, unexplained raised alkaline phosphatase, prior skeletal radiation, and open epiphyses.
• Always follow an anabolic course with an antiresorptive, with no gap.
• Never stop denosumab without a plan; avoid switching straight from denosumab to a PTH analog.
• Combination therapy increases BMD but has no fracture data and is not standard.
• Check P1NP at one to three months to confirm response to PTH-pathway agents.

Frequently Asked Questions

Is anabolic therapy safe after denosumab?

It can be used, but with care. Switching straight from denosumab to teriparatide causes transient bone loss, particularly at the hip, and stopping denosumab risks rebound vertebral fractures. Romosozumab is usually preferred after denosumab, or a bridging strategy with overlap or zoledronic acid is used; seek specialist advice.

Can anabolic and antiresorptive drugs be combined?

Teriparatide plus denosumab increases BMD more than either alone, but there are no fracture outcome data and cost is high. Combination therapy is reserved for selected patients in specialist settings. The standard approach is sequential: anabolic first, then antiresorptive.

What side effects do teriparatide, abaloparatide, and romosozumab cause?

Teriparatide commonly causes dizziness, leg cramps, nausea, and transient hypercalcemia. Abaloparatide causes dizziness, palpitations, and injection-site redness, and the first dose should be given sitting or lying down. Romosozumab most often causes joint pain, headache, and injection-site reactions, with hypocalcemia and a cardiovascular warning as the key concerns.

Who should not take romosozumab?

Patients who had an MI or stroke in the past year, those with uncorrected hypocalcemia, and those with hypersensitivity to the drug. Use caution in patients with multiple cardiovascular risk factors and in severe renal impairment or dialysis because of hypocalcemia risk. It is not approved for men in the US.

Is abaloparatide better than teriparatide for hip fractures?

Abaloparatide produced larger hip BMD gains than teriparatide in ACTIVE, but the trial was not powered to compare hip fracture rates. Its hip advantage is therefore in BMD, not proven fracture reduction.

Can anabolic therapy be used after years of bisphosphonate treatment?

Yes. Stop the bisphosphonate and start the anabolic agent; no washout is needed. The teriparatide response may be blunted, especially at the hip, whereas romosozumab is less affected.

Why is romosozumab limited to 12 months while the others get 24?

Its bone-forming effect attenuates over the first year while the antiresorptive effect persists, so extra doses add little. Teriparatide and abaloparatide continue to stimulate formation into the second year.

What happens if a patient stops anabolic therapy without an antiresorptive?

BMD gains are gradually lost over the following one to two years, and fracture protection wanes. Failing to start follow-on therapy is one of the most common prescribing errors with these drugs.

For the full spectrum of diagnosis and treatment, see our osteoporosis guide.