Bone Mineral Density and Hyperthyroidism
Bone mineral density (BMD) is a measure of how much mineral (mainly calcium and phosphate) is packed into bone tissue. Reduced BMD indicates weaker bones and increased fracture risk.
Mechanism: How Hyperthyroidism Reduces BMD
Excess thyroid-hormones accelerate bone turnover — the cycle of bone resorption (breakdown by osteoclasts) and bone formation (by osteoblasts). When bone is broken down faster than it can be rebuilt, net bone loss occurs. Long-standing untreated hyperthyroidism can significantly reduce BMD, leading to:
- Osteoporosis — porous, fragile bones
- Increased fracture risk (especially hip, spine, wrist)
This is a systemic complication of hyperthyroidism beyond the classic metabolic symptoms.
Protective Nutrients
- calcium: Essential raw material for bone mineralisation. Adults need approximately 700–1000 mg/day. Dairy is the richest source, but note iodine content; broccoli and kale are good low-iodine alternatives.
- vitamin-d: Required for intestinal calcium absorption. Deficiency is common in hyperthyroid patients. NHS recommends 10 mcg/day supplementation in autumn/winter.
- Treating the underlying hyperthyroidism is the most important intervention.
Management
- Treat hyperthyroidism (antithyroid drugs, radioactive-iodine-treatment, or surgery)
- Ensure adequate calcium and vitamin-d intake
- Consider DEXA bone density scan if hyperthyroidism was long-standing or severe
- Weight-bearing exercise supports bone density