From the Guidelines
Hyperthyroidism can cause hypercalcemia through increased bone resorption, and treatment should focus on addressing the underlying hyperthyroidism. When thyroid hormone levels are elevated, osteoclast activity increases, releasing more calcium from bones into the bloodstream 1. This thyrotoxicosis-induced hypercalcemia typically presents with mild to moderate elevations in serum calcium (usually <12 mg/dL) and is found in approximately 15-20% of patients with hyperthyroidism.
Key Considerations
- Treatment focuses primarily on addressing the underlying hyperthyroidism with antithyroid medications like methimazole (starting at 10-30 mg daily) or propylthiracil (100-300 mg daily in divided doses) 1.
- Beta-blockers such as propranolol (40-120 mg daily) can help control symptoms while waiting for thyroid function to normalize.
- Supportive measures for hypercalcemia include adequate hydration and sometimes bisphosphonates in severe cases.
- Once the hyperthyroidism is controlled, calcium levels typically normalize within weeks.
- It's essential to exclude other causes of hypercalcemia, such as primary hyperparathyroidism, which can coexist with hyperthyroidism, as noted in guidelines for bone metabolism and disease in chronic kidney disease 1.
Monitoring and Follow-up
- Monitoring both thyroid function tests and calcium levels is essential during treatment to ensure resolution of both conditions.
- Regular follow-up appointments with a healthcare provider are necessary to adjust treatment as needed and prevent complications.
From the Research
Hyperthyroidism and Hypercalcemia
- Hyperthyroidism is a condition where the thyroid gland produces and secretes inappropriately high amounts of thyroid hormone, which can lead to thyrotoxicosis 2.
- Hypercalcemia, on the other hand, is a condition characterized by elevated calcium levels in the blood, which can be caused by various factors, including primary hyperparathyroidism, malignancy, and endocrinopathies such as thyroid disease 3.
- The relationship between hyperthyroidism and hypercalcemia is not fully understood, but it is known that hyperthyroidism can contribute to hypercalcemia in some cases 3.
- Hyperthyroidism can be treated with antithyroid medications, radioactive iodine ablation, or surgery, depending on the underlying cause and severity of the condition 4, 2, 5.
- Hypercalcemia, if caused by hyperthyroidism, may be managed by treating the underlying hyperthyroidism, in addition to other treatments such as hydration and intravenous bisphosphonates 3.
Causes and Symptoms
- Hyperthyroidism can be caused by Graves' disease, toxic multinodular goiter, toxic adenoma, and other conditions 4, 2, 5.
- Symptoms of hyperthyroidism include anxiety, insomnia, palpitations, unintentional weight loss, diarrhea, and heat intolerance 5.
- Hypercalcemia can cause symptoms such as nausea, vomiting, dehydration, confusion, somnolence, and coma, especially if severe 3.
Treatment and Management
- Treatment of hyperthyroidism depends on the underlying cause and severity of the condition, and may involve antithyroid medications, radioactive iodine ablation, or surgery 4, 2, 5.
- Hypercalcemia caused by hyperthyroidism may be managed by treating the underlying hyperthyroidism, in addition to other treatments such as hydration and intravenous bisphosphonates 3.
- Beta blockers may be used as adjuvant therapy in the treatment of hyperthyroidism, especially in cases where symptoms such as palpitations and tremors are present 6.