Parathyroid adenoma (most common), parathyroid hyperplasia, parathyroid carcinoma
Milk alkali syndrome
Granulomatous
Secondary<unk>  (response to hypocalcemia)
Tertiary<unk>  due to CKD
Hyperparathyroidism
Addison's disease
Hypoparathyroidism
Calciphylaxis
Hypothyroidism
Excess vitamin D
Hyperthyroidism
Hypercalcemia of malignancy