Fractures, particularly hip and spine fractures, are a major cause of mortality and morbidity among older individuals. The term “osteoporosis” indicates increased porosity of bones resulting in low bone density; increased bone fragility; and an increased risk for fracture, often with minimal trauma.
During the adolescent years, bone accrues at a rapid rate, and optimal bone accrual during this time is essential to attain optimal peak bone mass, typically achieved in the third decade of life. Bone mass then stays stable until the 40s-50s, after which it starts to decline. One’s peak bone mass sets the stage for both immediate and future bone health. Individuals with lower peak bone mass tend to have less optimal bone health throughout their lives, and this becomes particularly problematic in older men and in the postmenopausal years for women.
One’s genes have a major impact on bone density and are currently not modifiable.
Modifiable factors include mechanical loading of bones through exercise activity, maintaining a normal body weight, and ensuring adequate intake of micronutrients (including calcium and vitamin D) and macronutrients. Medications such as glucocorticoids that have deleterious effects on bones should be limited as far as possible. Endocrine, gastrointestinal, renal, and rheumatologic conditions and others, such as cancer, which are known to be associated with reduced bone density and increased fracture risk, should be managed appropriately.
A deficiency of the gonadal hormones (estrogen and testosterone) and high blood concentrations of cortisol are particularly deleterious to bone. Hormone replacement therapy in those with gonadal hormone deficiency and strategies to reduce cortisol levels in those with hypercortisolemia are essential to prevent osteoporosis and also improve bone density over time. The same applies to management of conditions such as anorexia nervosa, relative energy deficiency in sports, inflammatory bowel disease, celiac disease, cystic fibrosis, chronic kidney disease, and chronic arthritis.
Once osteoporosis has developed, depending on the cause, these strategies may not be sufficient to completely reverse the condition, and pharmacologic therapy may be necessary to improve bone density and reduce fracture risk. This is particularly an issue with postmenopausal women and older men. In these individuals, medications that increase bone formation or reduce bone loss may be necessary.
Medications that reduce bone loss include bisphosphonates and denosumab; these are also called “antiresorptive medications” because they reduce bone resorption by cells called osteoclasts. Bisphosphonates include alendronate, risedronate, ibandronate, pamidronate, and zoledronic acid, and these medications have direct effects on osteoclasts, reducing their activity. Some bisphosphonates, such as alendronate and risedronate, are taken orally (daily, weekly, or monthly, depending on the medication and its strength), whereas others, such as pamidronate and zoledronic acid, are administered intravenously: every 3-4 months for pamidronate and every 6-12 months for zoledronic acid. Ibandronate is available both orally and intravenously.
Denosumab is a medication that inhibits the action of receptor activator of nuclear factor-kappa ligand 1 (RANKL), which otherwise increases osteoclast activity. It is administered as a subcutaneous injection every 6 months to treat osteoporosis. One concern with denosumab is a rapid increase in bone loss after its discontinuation.
Medications that increase bone formation are called bone anabolics and include teriparatide, abaloparatide, and romosozumab. Teriparatide is a synthetic form of parathyroid hormone (recombinant PTH1-34) administered daily for up to 2 years. Abaloparatide is a synthetic analog of parathyroid hormone–related peptide (PTHrP), which is also administered daily as a subcutaneous injection. Romosozumab inhibits sclerostin (a substance that otherwise reduces bone formation and increases bone resorption) and is administered as a subcutaneous injection once a month. Effects of these medications tend to be lost after they are discontinued.
In 2019, the Endocrine Society published guidelines for managing postmenopausal osteoporosis. The guidelines recommend lifestyle modifications, including attention to diet, calcium and vitamin D supplements, and weight-bearing exercise for all postmenopausal women. They also recommend assessing fracture risk using country-specific existing models.
Guidelines vary depending on whether fracture risk is low, moderate, or high. Patients at low risk are followed and reassessed every 2-4 years for fracture risk. Those at moderate risk may be followed similarly or prescribed bisphosphonates. Those at high risk are prescribed an antiresorptive, such as a bisphosphonate or denosumab, or a bone anabolic, such as teriparatide or abaloparatide (for up to 2 years) or romosozumab (for a year), with calcium and vitamin D and are reassessed at defined intervals for fracture risk; subsequent management then depends on the assessed fracture risk.
People who are on a bone anabolic should typically follow this with an antiresorptive medication to maintain the gains achieved with the former after that medication is discontinued. Patients who discontinue denosumab should be switched to bisphosphonates to prevent the increase in bone loss that typically occurs.
In postmenopausal women who are intolerant to or inappropriate for use of these medications, guidelines vary depending on age (younger or older than 60 years) and presence or absence of vasomotor symptoms (such as hot flashes). Options could include the use of calcium and vitamin D supplements; hormone replacement therapy with estrogen with or without a progestin; or selective estrogen receptor modulators (such as raloxifene or bazedoxifene), tibolone, or calcitonin.
It’s important to recognize that all pharmacologic therapy carries the risk for adverse events, and it’s essential to take the necessary steps to prevent, monitor for, and manage any adverse effects that may develop.
Managing osteoporosis in older men could include the use of bone anabolics and/or antiresorptives. In younger individuals, use of pharmacologic therapy is less common but sometimes necessary, particularly when bone density is very low and associated with a problematic fracture history — for example, in those with genetic conditions such as osteogenesis imperfecta. Furthermore, the occurrence of vertebral compression fractures often requires bisphosphonate treatment regardless of bone density, particularly in patients on chronic glucocorticoid therapy.
Preventing osteoporosis is best managed by paying attention to lifestyle; optimizing nutrition and calcium and vitamin D intake; and managing conditions and limiting the use of medications that reduce bone density.
However, in certain patients, these measures are not enough, and pharmacologic therapy with bone anabolics or antiresorptives may be necessary to improve bone density and reduce fracture risk.
Dr. Misra, of the University of Virginia and UVA Health Children’s Hospital, Charlottesville, disclosed ties with AbbVie, Sanofi, and Ipsen.
A version of this article appeared on Medscape.com.