iPTH should be eval with Sr. Ca levels, Sr. Phosphate and urine electrolytes to aid in its interpretation.
PTH: 7 - 53 pg/mL with Total Ca: 8.6 - 10.6 mg/dL = NORMAL
PTH: >53. Tot. Ca: >10.6 = 1° hyperparathyroidism
PTH: >53. Tot. Ca: <10.6 = 2° hyperparathyroidism
PTH: <45. Tot. Ca: >10.6 = Non-parathyroid hypercalcemia
PTH: <20. Tot. Ca: >8.6 - Hypoparathyroidism
Total Ca should be corrected for low albumin.
If blood pH is not normal, an ionized Ca should be done.
In primary hyperparathyroidism: hypercalcemia, PTH level in high-normal range; hypophosphatemia, hypercalciuria.
Clear surgical indications for primary hyperparathyroidism:
Serum Ca greater than 1 mg/dL above the upper limit of normal.
BMD by DXA: T-score < - 2.5 at lumbar spine, total hip, femoral neck, or distal 1/3 radius.
Vertebral fracture
Creatinine clearance < 60
24-h urine for calcium > 400 mg/d ( 10 mmol/d) and/or increased stone risk by biochemical stone risk analysis
Presence of nephrolithiasis or nephrocalcinosis by x-ray, ultrasound, or CT
< 50 yrs