1. Thus a third cause of secondary hyperparathyroidism is chronic kidney disease. 2. Tertiary hyperparathyroidism has a high PTH and a high serum calcium. 3. _Who have hyperparathyroidism ( an overactive thyroid gland ). 4. One cause of hypercalcemia is a condition known as hyperparathyroidism . 5. After recognition, primary hyperparathyroidism should be proved or excluded. 6. A parathyroid adenoma is the most common cause of hyperparathyroidism . 7. Secondary hyperparathyroidism occurs if the calcium level is abnormally low. 8. Lithium-associated hyperparathyroidism is usually caused by a single parathyroid adenoma. 9. Hyperparathyroidism results in hypercalcaemia and its effects and in extreme bone wasting.10. Primary hyperparathyroidism is most commonly due to solitary parathyroid adenoma.