Tertiary hyperparathyroidism is-
High PO
4
 level with metastasis
Secondary hyperparathyroidism with CRF
Primary hyperparathyroidism with low Cam' levels
Secondary hyperparathyroidism with chief cell adenoma
Davidson states "In very small proportion of cases of secondary hyperparathyroidism continuous stimulation of the parathyroid may result in adenoma formation and autonomous PTH secretion. This is known as tertiary ​hyperparathyroidism".