Table 4.

Biochemical parameters in hypoparathyroidism.

Lab test	Looking for	Interval	Comments
Calcium	Hypocalcemia and hypercalcemia	At every check, every 6 months at steady state	Ionized calcium is preferable If not available, total calcium (and albumin-corrected) is acceptable Timing of assessment is dependent on previous/daily calcium intake by food or supplements, as well as treatment Calcium levels should be assessed several days after changes in active vitamin D analog doses or PTH doses to detect iatrogenic hypercalcemia
PTH		Only for diagnosis	Not required for follow-up in chronic HypoPT Should be assessed to detect recovery in transient post-surgical hypoparathyroidism (6–12 months after the surgery)
Phosphate	Hyperphosphatemia	At every check	Hyperphosphatemia can be related to high dietary phosphate intake (soft drinks, products with preservatives, acidifier, and flavor enhancer) Hyperphosphatemia is associated with higher risk of infections and with increased mortality (142)
Calcium–phosphate product			Should be calculated Associated with brain calcifications and reduced QoL in some (144, 145) but not all studies (3)
Kidney function	Renal insufficiency	At every check	To detect decline in renal function Advise patients to be careful with nephrotoxic medications and with dehydration (146)
25(OH)D	Vitamin D deficiency		Often high vitamin D doses needed, especially under PTH replacement therapy 25(OH)D recommended goal: >30 ng/mL and <50 ng/mL (>75 nmol/L and <125 nmol/L) (expert opinion (2))
Calciuria	Hypercalciuria	Every 6–12 months	24 -h calcium excretion is reliable and spot easier to obtain
Urinary stone profile		As clinically indicated	Sodium, urea, citrate, oxalate, pH, osmolarity, urate excretions, and others
Magnesium	Hypomagnesemia	Yearly or as clinically indicated	Serum magnesium does not reflect intracellular levels well and magnesium depletion is possible with normal values Hypomagnesemia reduces response to PTH and may cause hypokalemia
Thyroid status		At every check	In patients with thyroid replacement therapy

25(OH)D, 25-hydroxyvitamin D; HypoPT, chronic hypoparathyroidism; PTH, parathyroid hormone; rhPTH, recombinant human parathyroid hormone.