A 55-year-old man on long-term prednisolone for giant cell arteritis develops glucocorticoid-induced osteoporosis. The primary mechanism by which chronic glucocorticoid excess causes bone loss is:

• A Suppression of osteoblast activity and induction of osteoblast apoptosis ✓
• B Inhibition of calcium absorption from the renal tubules
• C Increased osteoblast-mediated bone formation
• D Direct stimulation of osteoclast activity via RANKL

Explanation

Glucocorticoids primarily cause bone loss by directly suppressing osteoblast proliferation, function, and survival. They inhibit type I collagen synthesis and promote osteoblast and osteocyte apoptosis. While glucocorticoids also increase RANKL expression, the dominant mechanism of bone loss is impaired bone formation due to osteoblast suppression. This makes bisphosphonates, which reduce resorption, and teriparatide, which stimulates formation, both relevant in management.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.