Table 2 |.

Biochemical features of various forms of hyperparathyroidism and FHH

Form of hyperparathyroidism	Calcium levels	PTH levels	Phosphate levels	Urinary calcium excretion
Primary hyperparathyroidism	Increased	Increased or inappropriately normal	Low or low-normal	FeCA typically >1–2%
Secondary hyperparathyroidism	Normal or low	Increased	Dependent on cause; low or low-normal in vitamin D deficiency or malabsorption; high or high-normal in renal failure	Dependent on cause; low in vitamin D deficiency or malabsorption; high in renal calcium leak
Tertiary hyperparathyroidism	Increased	Increased	Variable; dependent on before or after renal transplant	Low before renal transplant
Normocalcaemic primary hyperparathyroidism	Normal (total & ionized)	Increased	Normal	<350 mg per 24 h29
FHH	Increased	Increased or inappropriately normal; the majority have normal PTH	Normal	FeCa typically <1%

FeCa, fractional excretion of calcium; FHH, familial hypocalciuric hypercalcaemia; PTH, parathyroid hormone