Primary hyperparathyrodism 

• neoplasm

• familial 

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SECONdary hyperparathyroidism 

• IN CKD patients, persistently low calcium level causes persistently high parathyroid - to release calcium into the blood 

• vitamin D insufficiency 

• malabsorption

Tertiary hyperparathyrodisim 

in renal failure, longstanding high Parathyrod hormone causes persistenly elevated calcium due to autonomous release of calcium from bone - 

osteodystrophy