Hypothyroidism

Low bone mass and microarchitectural deterioration causing fragility fracture ris, primary (postmenopausal, age-related) or secondary (glucocorticoids , most common secondary cause, hyperthyroidism, hyperparathyroidism, hypogonadism, malabsorption, CKD, RA, immobilization).

Often asymptomatic until fracture ; vertebral compression (may be silent or cause acute pain/height loss/kyphosis), hip fractures (significant morbidity/mortality), wrist fractures (often earliest).

Risk factors: age, female sex, postmenopausal status, low BMI, smoking, excess alcohol, family history of hip fracture, prior fragility fracture (strongest predictor), glucocorticoid use, early menopause, malabsorption, immobility.

• DEXA scan: T-score normal ≥-1.0, osteopenia -1.0 to -2.5, osteoporosis ≤-2.5 (hip and lumbar spine)

• FRAX tool: 10-year fracture risk, guides treatment threshold

• Indications for DEXA: postmenopausal women with risk factors, women ≥65, men ≥70 or younger with risk factors, fragility fracture, long-term glucocorticoid use

• Secondary cause workup if indicated: calcium, phosphate, ALP, vitamin D, TSH, PTH, testosterone (men), celiac serology, myeloma screen if atypical

• Vertebral imaging if height loss/kyphosis/unexplained back pain

Differentials: osteomalacia (vitamin D deficiency, defective mineralization ; different treatment), multiple myeloma, metastatic bone disease, Paget's disease, primary hyperparathyroidism.

• Lifestyle: calcium 1000-1200mg/day, vitamin D supplementation if deficient (800-2000 IU/day), weight-bearing/resistance exercise, smoking cessation, alcohol moderation, fall prevention

• Pharmacological ; indicated for T-score ≤-2.5, fragility fracture, or high FRAX risk:

  • Bisphosphonates (first-line): alendronate 70mg once weekly, risedronate 35mg once weekly, or zoledronic acid 5mg IV annually ; empty stomach, remain upright 30-60 min (oral); rare risks with >5 years use: osteonecrosis of jaw, atypical femoral fracture

  • Denosumab (SC 6-monthly): alternative ; never stop without transition to bisphosphonate (rebound fracture risk)

  • Teriparatide/abaloparatide (anabolic, daily SC): severe osteoporosis ; 18-24 month course, followed by antiresorptive

  • Romosozumab: newer anabolic, 12-month course ; caution in CV disease history

• Glucocorticoid-induced: lower treatment threshold, consider prophylactic bisphosphonate with steroid initiation if ≥3 months anticipated at significant dose

• Monitoring: repeat DEXA ~every 2 years, periodic calcium/renal function

Referral: endocrinology/rheumatology for secondary osteoporosis workup, treatment failure, anabolic agent consideration, complex cases.