Evenity (Romosozumab) and Children Under 12: What Parents and Clinicians Need to Know

What Is Romosozumab and Who Is It Actually Approved For?

Romosozumab is a monoclonal antibody that targets sclerostin, a protein made by osteocytes that normally slows bone formation. By blocking sclerostin, the drug simultaneously increases bone building and decreases bone breakdown. This dual action distinguishes it from bisphosphonates or denosumab, which work only on the resorption side.

The FDA approved romosozumab in April 2019 under the brand name Evenity, specifically for postmenopausal women with osteoporosis at high or very high fracture risk. The approved regimen is 210 mg given as two subcutaneous injections once monthly for 12 months, after which patients transition to an antiresorptive agent such as alendronate or denosumab.

That approval is narrow by design. The key ARCH trial enrolled postmenopausal women with a mean age of 74, and the FRAME trial enrolled postmenopausal women with a mean age of 71. Neither trial included males, premenopausal women, or children.

Children under 12 are entirely outside the approved indication. Full stop.

Why the Pediatric Age Group Matters for This Drug

Parents and pediatric clinicians sometimes encounter romosozumab in discussions of rare pediatric bone disorders, such as osteogenesis imperfecta, hypophosphatasia, or juvenile osteoporosis. Sclerostin inhibition is theoretically interesting in some of these conditions because low bone mass in children carries lifelong fracture risk. Animal studies in young rodents showed that sclerostin inhibition increased trabecular and cortical bone mass, but rodent skeletal biology during growth differs substantially from human pediatric bone remodeling.

No completed randomized controlled trial of romosozumab in children under 12 has been published. The evidence simply does not exist to guide dosing, safety, or efficacy in this population.

How Bone Development Works in Girls Under 12

Girls build roughly 90 percent of peak bone mass before age 18, with the most rapid accrual occurring between ages 11 and 14 during the pubertal growth spurt. Peak bone mass is one of the strongest predictors of osteoporotic fracture risk decades later, which means anything that disrupts normal skeletal development during childhood has consequences that extend well into menopause and beyond.

The Role of Estrogen in Pediatric Female Bone

Estrogen is the primary driver of the adolescent bone density surge in girls. As estrogen rises during puberty, it suppresses osteoclast activity and increases osteoblast lifespan. Girls who experience estrogen deficiency before or during puberty, whether from hypothalamic amenorrhea, eating disorders, Turner syndrome, or premature ovarian insufficiency, lose bone at a rate that may never be fully recovered.

Sclerostin itself changes across life stages. In premenopausal women, sclerostin levels are relatively low. Sclerostin rises significantly after menopause, which is part of why postmenopausal women are the population in whom blocking it produces the largest clinical benefit. In growing children, sclerostin biology is still being mapped. Premature or inappropriate modification of sclerostin signaling during skeletal development carries unknown and potentially serious risks.

Growth Plates: A Specific Concern

Open epiphyseal growth plates in children under 12 represent a developmental feature absent in postmenopausal women. Any agent that alters the balance between bone formation and resorption could theoretically affect longitudinal bone growth, growth plate closure timing, or the microarchitecture of cortical bone during consolidation. No human data exist to confirm or rule out these effects for romosozumab in young children.

Clinical Evidence (or the Lack of It) in Children Under 12

The WomanRx editorial team reviewed all publicly available clinical trial registries and peer-reviewed publications as of January 2025. The evidence picture for romosozumab in pediatric populations can be summarized in three categories.

Completed and published trials: Zero trials in children under 12. The ARCH trial (Saag et al., NEJM 2017) and the FRAME trial (Cosman et al., NEJM 2016) remain the foundational efficacy data, and both are limited to postmenopausal women. In ARCH, romosozumab followed by alendronate reduced new vertebral fracture risk by 48 percent compared with alendronate alone over 24 months.

Animal and preclinical data: Preclinical studies in growing mice and rats showed increased bone mass with sclerostin inhibition, but the FDA label explicitly notes that juvenile animal studies revealed changes in growth plate morphology at high doses. These findings were not fully characterized before approval, and the label advises against use in pediatric patients.

Rare disease case reports and off-label exploration: A small number of case reports describe sclerostin inhibitor use in osteogenesis imperfecta in children, but these are isolated reports, not controlled trials, and they do not establish safety or dosing guidelines for the under-12 population.

What Guidelines Say

Neither the American College of Obstetricians and Gynecologists nor the Endocrine Society has issued guidance supporting romosozumab use in children. The FDA prescribing information contains no pediatric dosing section for patients under 12 because no data have been submitted to support one.

Pediatric bone specialists typically follow a framework anchored in bisphosphonates for secondary osteoporosis in children, with calcium and vitamin D as foundational therapy across all ages.

Pregnancy and Lactation: Mandatory Information for Any Woman Considering This Drug

Romosozumab is contraindicated in pregnancy. This applies to adolescent girls who have reached reproductive age, women in the trying-to-conceive window, and any woman of childbearing potential who has not confirmed reliable contraception.

Pregnancy Safety Data

Animal studies showed fetal harm at doses below the human therapeutic dose. The FDA label states that romosozumab caused fetal skeletal abnormalities and increased fetal loss in cynomolgus monkey studies at exposures similar to the human dose. No adequate, well-controlled studies in pregnant women exist. Given these findings and the biologic plausibility of fetal harm from altered sclerostin signaling during skeletal development, pregnancy must be excluded before starting treatment.

Women of reproductive potential are advised to use effective contraception during treatment and for at least 3 months after the last dose, consistent with the drug's half-life of approximately 6.4 days.

Lactation

It is not known whether romosozumab is excreted in human milk. Because of the potential for serious adverse effects on the nursing infant's skeletal development, breastfeeding is not recommended during romosozumab treatment.

Postmenopausal Status and Why It Matters

The approved indication presupposes that patients are postmenopausal, meaning spontaneous amenorrhea for at least 12 months or surgical menopause. For a woman who has reached natural menopause, the pregnancy concern is moot. For any woman still menstruating, including perimenopausal women who may ovulate sporadically, pregnancy testing and contraception remain medically necessary before and during treatment.

Female-Specific Conditions Where Bone Health Is Relevant in Young Girls

Several conditions affecting girls under 12 or adolescents carry significant bone density implications. None of them have romosozumab as an approved or guideline-supported treatment option, but they are worth naming so that parents understand the distinction between the conditions and the drug.

Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is a genetic disorder of collagen production causing fragile bones and frequent fractures from birth. Intravenous bisphosphonates, particularly pamidronate, have the strongest evidence base for OI in children and remain the standard of care in pediatric practice. Sclerostin inhibition is under investigation as a potential add-on strategy in adults with OI, but no pediatric trial has confirmed safety or benefit.

Juvenile Idiopathic Osteoporosis

Juvenile idiopathic osteoporosis is a rare, self-limited condition typically appearing before puberty and resolving spontaneously at the onset of puberty. Bisphosphonates are used in severe cases. Romosozumab has no established role here.

Eating Disorders and the Female Athlete Triad

Anorexia nervosa and the female athlete triad (low energy availability, menstrual dysfunction, low bone density) are significant causes of low bone mass in adolescent girls. Relative energy deficiency in sport (RED-S) can cause permanent bone loss if untreated during the adolescent growth window. The treatment priority in these girls is restoring estrogen through weight restoration and menstrual recovery, not adding a bone anabolic agent.

Turner Syndrome

Girls with Turner syndrome often have low estrogen from gonadal dysgenesis and reach adulthood with significantly lower bone density than age-matched controls. Estrogen replacement therapy, initiated at an age-appropriate time, is the foundational treatment. Romosozumab has not been studied in Turner syndrome.

Who This Drug Is Right For (and Not Right For): A Life-Stage Framework

Understanding where romosozumab fits requires clarity about who it was designed to treat and who carries unacceptable risk.

Women This Drug Is Designed For

Postmenopausal women who meet all of the following criteria are the appropriate candidates:

• Confirmed postmenopausal status (natural or surgical)
• Osteoporosis on DXA (T-score of -2.5 or below at spine or hip) or a prior fragility fracture
• High or very high fracture risk as defined by the Endocrine Society's 2019 clinical practice guideline
• No history of myocardial infarction or stroke in the prior 12 months (due to the FDA's boxed warning on cardiovascular risk)
• No current or planned pregnancy

Women and Girls This Drug Is Not Appropriate For

• Children under 12: no approved indication, no safety data, potential growth plate risk
• Adolescents under 18: no controlled trials; immature skeletal system; open growth plates
• Premenopausal women: off-label, limited data, pregnancy risk
• Perimenopausal women still menstruating: pregnancy must be excluded; discuss with specialist
• Pregnant women: contraindicated
• Breastfeeding women: avoid; unknown milk transfer
• Women with MI or stroke in the past year: contraindicated per FDA boxed warning

What Parents Should Actually Do If Their Daughter Has Low Bone Density

A DXA scan showing low bone density in a child under 12 is alarming for any parent. Here are the concrete steps that align with evidence and guidelines.

Step 1. Get a specialist referral. Pediatric endocrinology or a metabolic bone disease center should evaluate any child with unexplained low bone density or frequent fragility fractures. A general practitioner or telehealth platform is not the right setting to manage pediatric bone disorders.

Step 2. Investigate the cause. Low bone density in children is almost always secondary to another condition: malabsorption (celiac disease, inflammatory bowel disease), glucocorticoid therapy, renal disease, eating disorders, or a genetic bone disorder. The International Society for Clinical Densitometry advises against diagnosing osteoporosis in children on DXA alone without a significant fracture history.

Step 3. Optimize foundational therapy. Children aged 4 to 8 need 1,000 mg of calcium daily; ages 9 to 18 need 1,300 mg. Vitamin D deficiency should be corrected with supplementation. Weight-bearing physical activity 60 minutes daily supports bone accrual during the growth window.

Step 4. Discuss bisphosphonates if warranted. For children with OI or severe secondary osteoporosis with fractures, intravenous pamidronate or zoledronic acid are the most evidence-supported pharmacologic options. Oral alendronate has been used off-label in some pediatric populations.

Step 5. Avoid unapproved agents. Romosozumab, teriparatide, and abaloparatide are not appropriate for children under 18 outside of closely monitored clinical trials with institutional review board approval.

The Evidence Gap: What We Need That We Do Not Have

Women have been historically under-represented in bone disease research, and children are even further behind. The current state of evidence for romosozumab in pediatric populations reflects a broader failure to fund and conduct trials in vulnerable populations.

Sclerostin's precise role in human pediatric skeletal maturation is not fully mapped. Genome-wide association studies have identified SOST gene variants that influence bone mineral density across the lifespan, but how acute pharmacologic blockade of sclerostin affects growth plate function, cortical consolidation, or long-term bone geometry in girls under 12 remains unstudied.

The Pediatric Bone Society and the International Osteoporosis Foundation have called for more pediatric skeletal research, but as of January 2025, no phase 2 or phase 3 trial of romosozumab in children under 12 is listed as recruiting on ClinicalTrials.gov. Parents and clinicians asking about this drug for a child under 12 are, in honest terms, asking about an unanswered question. Saying so plainly is more useful than suggesting the data will arrive soon.

Cardiovascular Safety: The Boxed Warning Every Woman Should Know

The FDA added a boxed warning to romosozumab based on data from the ARCH trial, which showed a higher rate of serious cardiovascular events, specifically myocardial infarction and stroke, in the romosozumab group compared with the alendronate group: 2.5 percent versus 1.9 percent over 12 months. This difference was statistically significant.

The cardiovascular concern does not apply directly to children under 12 with no known vascular disease, but it is part of the overall risk profile that explains why this drug requires specialist oversight, careful patient selection, and monitoring even in the approved population.

Any postmenopausal woman with a history of MI or stroke within the preceding 12 months should not receive romosozumab. The Menopause Society advises that the cardiovascular benefit-risk balance must be individualized for each patient.