Osteoporosis

INTRODCUCTION

Osteoporosis is a bone disorder characterized by low bone density, impaired bone architecture, and compromised bone strength predisposing to fracture.

CLINICAL PRESENTATION

• Many patients are unaware that they have osteoporosis and only present after fracture. Fractures can occur after bending, lifting, or falling or independent of any activity.
• The most common fractures involve vertebrae, proximal femur, and distal radius (wrist or Coles fracture). Vertebral fractures may be asymptomatic or present with moderate to severe back pain that radiates down a leg. Pain usually subsides after 2 to 4 weeks, but residual low-back pain may persist. Multiple vertebral fractures decrease height and sometimes curve the spine (kyphosis or lordosis) with or without significant back pain.
• Patients with a nonvertebral fracture frequently present with severe pain, swelling, and reduced function and mobility at the fracture site.

DIAGNOSIS

• The World Health Organization (WHO) fracture prediction model for treatment risk stratification uses these risk factors to predict the percent probability of fracture in the next 10 years: age, race/ethnicity, sex, previous fragility fracture, parent history of hip fracture, body mass index, glucocorticoid use, current smoking, alcohol (three or more drinks per day), rheumatoid arthritis, and select secondary causes with femoral neck BMD data optional.
• Physical examination findings: bone pain, postural changes (i.e., kyphosis), and loss of height (>1.5 in [3.8 cm]).
• Laboratory testing: complete blood count, creatinine, blood urea nitrogen, calcium, phosphorus, alkaline phosphatase, albumin, thyroid-stimulating hormone, free testosterone, 25-hydroxyvitamin D, and 24-hour urine concentrations of calcium and phosphorus.
• Measurement of central (hip and spine) BMD with dual-energy x-ray absorptiometry (DXA) is the diagnostic standard. Measurement at peripheral sites (forearm, heel, and phalanges) with ultrasound or DXA is used only for screening and for determining need for further testing
• A T-score compares the patient’s measured BMD to the mean BMD of a healthy, young (20- to 29-year-old), gender-matched, white reference population. The T-score is the number of standard deviations from the mean of the reference population.
• Diagnosis of osteoporosis is based on low-trauma fracture or central hip and/or spine DXA using WHO T-score thresholds. Normal bone mass is T-score above −1, low bone mass (osteopenia) is T-score between −1 and −2.4, and osteoporosis is T-score at or below −2.5.

TREATMENT: Goals of Treatment

The primary goal of osteoporosis care is prevention. Optimizing peak bone mass when young reduce the future incidence of osteoporosis. After low bone mass or osteoporosis develops, the objective is to stabilize or improve bone mass and strength and prevent fractures. Goals in patients with osteoporotic fractures include reducing pain and deformity, improving function, reducing falls and fractures, and improving quality of life.

Calcium Supplementation

Calcium increases BMD, but its effects are less than those of other therapies. Fracture prevention is only documented with concomitant vitamin D therapy; calcium should be combined with vitamin D and osteoporosis medications when needed. Because the fraction of calcium absorbed decreases with increasing dose, maximum single doses of 600 mg or less of elemental calcium are recommended.

• Calcium carbonate is the salt of choice because it contains the highest concentration of elemental calcium (40%) and is least expensive. Vitamin D supplementation maximizes intestinal calcium absorption and BMD; it may also reduce fractures and falls.
• Supplementation is usually provided with daily nonprescription cholecalciferol (vitamin D3) products. Higher-dose prescription ergocalciferol (vitamin D2) regimens given weekly, monthly, or quarterly may be used for replacement and maintenance therapy.

Bisphosphonates

Them long biologic half-lives of up to 10 years.

• Of the antiresorptive agents available, bisphosphonates provide some of the higher BMD increases and fracture risk reductions. Fracture reductions are demonstrated as early as 6 months

Denosumab

Denosumab (Prolia) is a RANK ligand inhibitor that inhibits osteoclast formation and increases osteoclast apoptosis. It is indicated for treatment of osteoporosis in women and men at high risk for fracture. It is also approved to increase bone mass in men receiving androgen-deprivation therapy for nonmetastatic prostate cancer and in women receiving adjuvant aromatase inhibitor therapy for breast cancer who are at high risk for fracture.

Calcitonin

Calcitonin is an endogenous hormone released from the thyroid gland when serum calcium is elevated. Salmon calcitonin is used clinically because it is more potent and longer lasting than the mammalian form.

• Calcitonin is indicated for osteoporosis treatment for women at least 5 years past menopause. It is reserved as a last-line treatment because efficacy is less robust than with other antiresorptive therapies.