Skeletal disorder of reduced bone strength and increased fracture risk; managed with bone-protective lifestyle and antiresorptive or anabolic therapy.
Also known as: osteoporosis, low bone density, fragility fracture
Overview
Skeletal disorder characterized by compromised bone strength predisposing to fracture. Defined operationally by bone mineral density T-score ≤ -2.5 at the femoral neck, total hip, or lumbar spine, OR by a hip or vertebral fragility fracture (low-energy fracture from a fall from standing height or less) regardless of BMD, or a proximal humerus, pelvis, or distal forearm fragility fracture with osteopenia. T-score between -1.0 and -2.5 is osteopenia (low bone mass).
Epidemiology
Affects ~10 million US adults; estimated 50% of women and 20% of men over 50 will have an osteoporotic fracture in their lifetime. Hip fractures carry ~20-30% 1-year mortality.
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Question 1MusculoskeletalMedium
A 55-year-old postmenopausal woman sustains a distal radius fracture after a fall from standing height. She has no prior fractures and takes no medications that affect bone. Dual-energy x-ray absorptiometry shows a T-score of -2.8 at the femoral neck. Serum calcium and renal function are normal. Which of the following is the most appropriate pharmacologic treatment?
AMenopausal hormone therapy with calcium and vitamin D
BCalcium and vitamin D supplementation alone
CRaloxifene therapy with calcium and vitamin D
DCalcitonin nasal spray with calcium and vitamin D
EOral bisphosphonate with calcium and vitamin D
Reveal answer & full explanation
Correct answer: E — Oral bisphosphonate with calcium and vitamin D
AMenopausal hormone therapy with calcium and vitamin D
BCalcium and vitamin D supplementation alone
CRaloxifene therapy with calcium and vitamin D
DCalcitonin nasal spray with calcium and vitamin D
EOral bisphosphonate with calcium and vitamin D✓
Why Oral bisphosphonate with calcium and vitamin D is correct
This woman has osteoporosis by both criteria: a T-score of -2.8 (at or below -2.5) and a low-trauma fragility fracture of the distal radius.
Per ACP 2023 and Endocrine Society guidance, an oral bisphosphonate such as alendronate or risedronate is first-line therapy and substantially reduces both vertebral and hip fracture risk; AACE 2020 classes a fracture within the past 12 months as very high risk and prefers an anabolic agent, denosumab, or IV zoledronic acid, but among the options offered an oral bisphosphonate remains the best choice.
Normal serum calcium and renal function clear the key prerequisites for starting an oral bisphosphonate.
Calcium and vitamin D are co-administered to provide adequate substrate for the antiresorptive effect.
Why the others are wrong
Calcitonin nasal spray with calcium and vitamin D — calcitonin has weak antifracture efficacy (modest vertebral benefit only) and is reserved for patients who cannot take other agents (buzzword-matching a drug approved for postmenopausal osteoporosis without weighing efficacy).
Calcium and vitamin D supplementation alone — supplementation is necessary adjunctive care but is insufficient as sole therapy once osteoporosis or a fragility fracture is established (right-diagnosis-wrong-step).
Raloxifene therapy with calcium and vitamin D — raloxifene is a second-line SERM with no proven hip-fracture reduction and added VTE risk, reserved for when bisphosphonates are unsuitable (confused-with-first-line therapy).
Menopausal hormone therapy with calcium and vitamin D — estrogen does reduce vertebral and hip fractures, as the WHI showed, which tempts in a 55-year-old postmenopausal woman, but its thromboembolic and stroke risks (plus breast cancer risk when combined with a progestin) make it a second-line option for osteoporosis, considered mainly when vasomotor symptoms also need treatment or bisphosphonates are unsuitable (confused-with-first-line therapy).
Question 2MusculoskeletalMedium
A 65-year-old woman with osteoporosis has been taking oral alendronate for 5 years. Her most recent lumbar spine T-score is -3.1, she has no history of fragility fracture, and her bone density has been stable. She asks whether she can take a drug holiday. Which of the following is the most appropriate next step?
ASwitch to denosumab for 2 years then stop
BRepeat dual-energy X-ray absorptiometry in 5 years
CInitiate a bisphosphonate drug holiday
DTransition to raloxifene maintenance therapy
EContinue alendronate for an additional 5 years
Reveal answer & full explanation
Correct answer: E — Continue alendronate for an additional 5 years
ASwitch to denosumab for 2 years then stop
BRepeat dual-energy X-ray absorptiometry in 5 years
CInitiate a bisphosphonate drug holiday
DTransition to raloxifene maintenance therapy
EContinue alendronate for an additional 5 years✓
Why Continue alendronate for an additional 5 years is correct
A T-score of -3.1 places this patient in the high (very high) fracture-risk category regardless of how many treatment years have elapsed; risk—not duration of therapy—drives the holiday decision (ACOG/Endocrine Society/AACE)
For high-risk patients, oral bisphosphonate therapy is continued for a total of up to 10 years (or IV zoledronic acid for up to 6 years) rather than being stopped
A drug holiday is reserved for patients who become low-to-moderate risk after 3-5 years (no fractures and a T-score above -2.5); this patient does not qualify
Continuing therapy maintains fracture protection while fracture risk is reassessed periodically
Why the others are wrong
Initiate a bisphosphonate drug holiday — a holiday is inappropriate at a T-score of -3.1 because residual high fracture risk persists; elapsed treatment years alone do not justify stopping (anchoring on duration)
Repeat dual-energy X-ray absorptiometry in 5 years — deferring reassessment for 5 years while leaving a high-risk patient untreated abandons fracture protection and ignores guideline monitoring intervals (false reassurance)
Transition to raloxifene maintenance therapy — raloxifene reduces vertebral fractures but has never shown hip or nonvertebral fracture benefit, so moving a patient with a T-score of -3.1 onto it downgrades protection rather than maintaining it (wrong-agent-for-risk)
Switch to denosumab for 2 years then stop — moving to a different antiresorptive can look like a way to give her a break from bisphosphonates, but stopping denosumab without a follow-on antiresorptive can trigger rapid rebound bone loss and multiple vertebral fractures, so this plan leaves a patient with a T-score of -3.1 less protected than continuing alendronate (planned rebound)
Additional high-yield points
Holiday eligibility hinges on becoming low-to-moderate risk: no hip or vertebral fracture and a T-score above -2.5
Very-high-risk patients (e.g., T-score at or below -3.0, prior fracture) may instead be transitioned to an anabolic agent such as teriparatide or romosozumab
Denosumab must not be stopped without transitioning to another antiresorptive because of rebound vertebral fractures
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Non-modifiable: age >65, female sex, postmenopausal status, white or Asian ancestry, family history of hip fracture, low body weight, prior fragility fracture
Modifiable: tobacco use, excessive alcohol (>3 drinks/day), low calcium and vitamin D intake, sedentary lifestyle
Medications: chronic glucocorticoids (prednisone ≥2.5 mg/day for >3 months per ACR 2022; risk rises with dose), aromatase inhibitors, androgen deprivation, PPIs, SSRIs, anticonvulsants, heparin, thiazolidinediones
Endocrine: hyperthyroidism, hyperparathyroidism, hypogonadism, Cushing syndrome, type 1 diabetes
Bone is in continuous turnover via osteoclast-mediated resorption and osteoblast-mediated formation. After peak bone mass (~age 30), resorption progressively exceeds formation. Estrogen withdrawal at menopause sharply increases osteoclast activity. Secondary causes (glucocorticoids, hyperparathyroidism) act through additional mechanisms — direct osteoblast suppression, increased RANKL signaling, and accelerated remodeling. The result is reduced trabecular connectivity and cortical thinning.
Clinical presentation
Symptoms
Asymptomatic until fracture occurs
Vertebral compression fracture: sudden back pain after minor strain, often spontaneous; can be silent
Loss of height >1.5 inches (4 cm) and progressive thoracic kyphosis
Hip, distal radius (Colles), pelvis, or proximal humerus fracture from low-energy fall
Signs / physical exam
Thoracic kyphosis ('dowager hump')
Loss of height
Rib-pelvis distance <2 finger-breadths
Tenderness to percussion over a fractured vertebra
Differential diagnosis
Osteomalacia — Defective mineralization from vitamin D deficiency or hypophosphatemia; bone pain, proximal weakness; low Ca, low phos, elevated alk phos, low 25-OH vitamin D
Metastatic bone disease — Known cancer or unexplained focal pain; lytic or blastic lesions; isolated fracture out of proportion
Hyperparathyroidism — Hypercalcemia, elevated PTH, subperiosteal resorption on imaging
Paget disease — Elevated alk phos with normal Ca/phos; bony enlargement and deformity; characteristic mosaic pattern on biopsy
Osteogenesis imperfecta — Childhood-onset fractures, blue sclerae, hearing loss, family history
Diagnostic workup
Labs
CBC, BMP, Ca, phos, Mg, 25-OH vitamin D, alkaline phosphatase
TSH, intact PTH
24-hour urine calcium and creatinine (rule out hypercalciuria, malabsorption)
Testosterone in men
Celiac serologies if anemia or low BMI
SPEP/UPEP/free light chains if anemia, renal dysfunction, or atypical fracture pattern
Bone turnover markers (CTX, P1NP) — useful for monitoring response, not for diagnosis
Imaging
Central DXA at lumbar spine and total hip (femoral neck) — diagnostic test
Vertebral fracture assessment (VFA) or lateral spine radiograph to detect silent vertebral fractures
FRAX calculator for 10-year fracture risk estimation
Other studies
Screening: women ≥65 — DXA for all (USPSTF 2025, B)
Screening: postmenopausal women <65 with ≥1 risk factor (e.g., low body weight, parental hip fracture, smoking, excess alcohol) who show increased risk on a clinical risk tool such as FRAX, OST, or ORAI (USPSTF 2025, B); no fixed FRAX cutoff
Screening: men — USPSTF finds insufficient evidence (I); the Endocrine Society suggests BMD testing at ≥70 and at 50-69 with risk factors
Screening: anyone after a fragility fracture
Screening: anyone on chronic glucocorticoids or other high-risk medications
Diagnostic algorithm
T-score Category
Definition
Action
Normal
≥ -1.0
Lifestyle counseling; rescreen per guideline
Osteopenia (low bone mass)
-1.0 to -2.5
Use FRAX; treat if FRAX ≥3% hip / ≥20% major OP fx
Osteoporosis
≤ -2.5
Pharmacologic therapy + Ca / vit D / exercise
Severe (established) osteoporosis
≤ -2.5 + fragility fracture
Same as above; consider anabolic agent if very high risk
WHO BMD classification by T-score and treatment thresholds.
Treatment
First-line
Calcium 1200 mg/day total (dietary preferred)
Vitamin D 800-2000 IU/day; target 25-OH vitamin D >30 ng/mL
Weight-bearing and resistance exercise
Fall prevention: home hazard assessment, balance training (tai chi), vision and medication review
Smoking cessation, limit alcohol to ≤2 drinks/day
Oral bisphosphonates — alendronate, risedronate, ibandronate (first-line; take fasting with water, remain upright 30-60 min); bind bone mineral and inhibit osteoclast farnesyl pyrophosphate synthase, causing osteoclast apoptosis
Avoid oral bisphosphonates with esophageal disorders or inability to remain upright; avoid bisphosphonates when CrCl is <35 mL/min (alendronate, zoledronic acid) or <30 mL/min (risedronate, ibandronate)
Indications for pharmacologic therapy
Treat patients with T-score ≤ -2.5, prior fragility hip or vertebral fracture, or FRAX ≥3% hip / ≥20% major osteoporotic fracture risk
Consider in glucocorticoid users at moderate-to-high risk
Other antiresorptives
IV bisphosphonates — zoledronic acid yearly, ibandronate quarterly (use if oral intolerance, malabsorption, or adherence concerns)
Denosumab (RANKL inhibitor) — subcutaneous every 6 months; not renally cleared, but carries an FDA boxed warning (2024) for severe hypocalcemia with eGFR <30 or dialysis, so evaluate for CKD-mineral bone disorder, replete calcium/vitamin D, and monitor calcium; do NOT discontinue without transitioning to a bisphosphonate (rebound fracture risk)
Raloxifene (SERM) — postmenopausal women with low risk for VTE; reduces vertebral fractures only (no proven hip or nonvertebral benefit); increases VTE risk and hot flashes; also reduces breast cancer risk
Estrogen — limited to women with menopausal symptoms; not first-line for osteoporosis alone
Calcitonin — weak antiresorptive with modest vertebral-only benefit and no hip fracture reduction; reserved for patients who cannot take other agents and used mainly for short-term analgesia after an acute vertebral fracture
Anabolic agents
Teriparatide and abaloparatide (PTH analogs) — daily SC, usually for up to 2 years (teriparatide may be continued longer only if fracture risk remains high); intermittent PTH1 receptor stimulation is anabolic, whereas continuous PTH excess (hyperparathyroidism) is resorptive; reserved for severe or high-risk osteoporosis (T-score ≤ -3.0, multiple vertebral fractures, fracture on antiresorptive therapy)
Avoid PTH analogs (osteosarcoma risk) with prior radiation therapy involving the skeleton, Paget disease or other metabolic bone disease, open epiphyses, or bone metastases/skeletal malignancy
Romosozumab (anti-sclerostin) — monthly SC for 12 months; high-risk postmenopausal women; black-box warning for cardiovascular events
After anabolic therapy ALWAYS transition to an antiresorptive to preserve gains
Bisphosphonate drug holiday
Consider after 5 years of oral or 3 years of IV bisphosphonate if low-to-moderate ongoing risk (T-score > -2.5, no recent fracture)
Continue treatment if T-score ≤ -2.5 at the hip or ongoing high risk (up to 10 years of oral or 6 years of IV bisphosphonate)
Complications
Hip, vertebral, distal radius, and other fragility fractures
Chronic pain, kyphosis, loss of height, reduced pulmonary function
Functional decline, dependency, increased mortality (especially after hip fracture)
Atypical femoral fracture (rare; long-term bisphosphonate or denosumab use)
Osteonecrosis of the jaw (rare; especially with dental procedures during high-dose IV bisphosphonate or denosumab)
PANCE pearls
Treat the patient, not just the T-score: a hip or vertebral fragility fracture establishes osteoporosis and warrants treatment regardless of T-score; a proximal humerus, pelvis, or distal forearm fragility fracture does so when BMD is in the osteopenic range.
Denosumab requires uninterrupted dosing — discontinuation without a bisphosphonate bridge causes rapid bone loss and multiple vertebral fractures.
FRAX score guides treatment thresholds in patients with osteopenia.
Anabolic therapy first in very high-risk patients yields greater BMD gains than antiresorptive-first; always follow with antiresorptive.
Always evaluate for and treat secondary causes — about 30% of women and 50% of men with osteoporosis have a contributing secondary cause.
References
USPSTF 2025 — USPSTF Recommendation Statement: Screening for Osteoporosis to Prevent Fractures (Nicholson WK et al., JAMA 2025;333:498-508)
NOF/BHOF 2022 — Clinician's Guide to Prevention and Treatment of Osteoporosis (Bone Health & Osteoporosis Foundation, 2022)
Endocrine Society 2019/2020 — Pharmacological Management of Osteoporosis in Postmenopausal Women: Endocrine Society Clinical Practice Guideline (Eastell et al., J Clin Endocrinol Metab 2019; 2020 update)
ACR 2022 — 2022 American College of Rheumatology Guideline for the Prevention and Treatment of Glucocorticoid-Induced Osteoporosis (Humphrey MB et al., Arthritis Rheumatol 2023;75:2088-2102)
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