From the Guidelines
Hyperthyroidism is associated with several skeletal complaints, including osteoporosis, increased fracture risk, bone pain, and muscle weakness, primarily due to accelerated bone turnover caused by excess thyroid hormone. The most common bone complaints include reduced bone mineral density, particularly in cortical bone, leading to fragility fractures even with minimal trauma 1. Patients may experience hypercalcemia in severe cases, causing additional symptoms like kidney stones and cardiac arrhythmias.
Key Skeletal Complaints
- Osteoporosis
- Increased fracture risk
- Bone pain
- Muscle weakness affecting mobility
Management and Treatment
Treatment focuses on managing the underlying hyperthyroidism with antithyroid medications, radioactive iodine therapy, or thyroidectomy 1. Bone health should be addressed with calcium supplementation (1000-1200mg daily), vitamin D (800-1000 IU daily), weight-bearing exercise, and in severe cases, bisphosphonates like alendronate (70mg weekly) or zoledronic acid (5mg IV annually) 1. Bone density testing is recommended at diagnosis and periodically during follow-up.
Considerations for Treatment
The decision to treat subclinical hyperthyroidism should consider the patient's age, risk for heart disease, osteopenia, or osteoporosis, and the presence of symptoms suggestive of hyperthyroidism 1. Younger individuals with subclinical hyperthyroidism and serum TSH persistently lower than 0.1 mIU/L may be offered therapy or follow-up depending on individual considerations. Prompt treatment of hyperthyroidism typically improves bone health, though some density loss may be permanent, especially in postmenopausal women.
From the Research
Skeletal Complaints Associated with Hyperthyroidism
The skeletal complaints associated with hyperthyroidism include:
- Osteoporosis: Hyperthyroidism is an established cause of high bone turnover with accelerated bone loss, leading to osteoporosis and increased fracture risk 2, 3, 4
- Low bone mineral density (BMD): Untreated hyperthyroidism is associated with accelerated bone turnover, low BMD and increased susceptibility to fragility fractures 3, 5
- Fragility fractures: Thyroid disorders have an important impact on bone metabolism and fracture risk, such that hyperthyroidism is associated with a decreased BMD and increased risk of fracture 3
- Compromised cortical microarchitecture: Hyperthyroid women had lower vBMD, lower estimated bone strength, and compromised cortical microarchitecture in the radius 6
- Decreased trabecular area and increased trabecular separation: After restoration of euthyroidism, significant improvements in vBMD and cortical microarchitecture were observed, but trabecular area decreased and trabecular separation increased 6
Effects of Hyperthyroidism Treatment on Bone Health
The effects of hyperthyroidism treatment on bone health include:
- Improvement in bone microarchitecture: Significant improvements in vBMD and cortical microarchitecture were observed after restoration of euthyroidism 6
- Increase in areal BMD: Areal BMD, measured by DXA, increased in the spine and in the hip after restoration of euthyroidism 6
- No association with increased risk of fractures: The genetic risk for hyperthyroid conditions was not associated with an increased risk of fractures 5