Parathyroid Disease Workup and Management

Initial Evaluation and Diagnosis

The initial workup for suspected parathyroid disease requires simultaneous measurement of serum calcium and PTH to differentiate PTH-dependent from PTH-independent hypercalcemia, followed by targeted evaluation based on this critical distinction, as recommended by clinical guidelines 1, 2
Serum calcium measurement is the cornerstone that determines urgency and direction of workup, according to the American College of Clinical Endocrinologists 1, 2
Intact PTH (iPTH) distinguishes primary hyperparathyroidism from PTH-independent causes, with elevated or inappropriately normal PTH indicating primary hyperparathyroidism, as stated by the Endocrine Society 1, 2
Serum phosphorus is typically low in primary hyperparathyroidism and PTHrP-mediated hypercalcemia, helping to differentiate from other causes, as noted by the National Institutes of Health 1
The American College of Clinical Endocrinologists recommends measuring serum albumin to correct total calcium if ionized calcium is unavailable 1
Vitamin D deficiency can mask the severity of hyperparathyroidism and must be assessed before surgical decisions, with a target 25-hydroxyvitamin D level of ≥50 nmol/L or 20 ng/mL, as recommended by the Endocrine Society 2
Serum creatinine and eGFR are essential to distinguish primary from secondary hyperparathyroidism related to chronic kidney disease, according to the National Kidney Foundation 3

Primary hyperparathyroidism is indicated by elevated calcium with elevated or inappropriately normal PTH, as diagnosed by the American College of Clinical Endocrinologists 2
The Endocrine Society recommends confirming vitamin D status and measuring 25-hydroxyvitamin D in primary hyperparathyroidism, with a target level of ≥50 nmol/L or 20 ng/mL 2
PTH-related protein (PTHrP) is elevated in malignancy-associated hypercalcemia, most commonly squamous cell lung cancer, occurring in 10-25% of lung cancer patients, as reported by the American Cancer Society 1
1,25-dihydroxyvitamin D is elevated in granulomatous disease or lymphoma, as noted by the Infectious Diseases Society of America 1
Secondary hyperparathyroidism is suggested by low or normal calcium with elevated PTH, often due to chronic kidney disease or vitamin D deficiency, as stated by the National Kidney Foundation 3
The American College of Clinical Endocrinologists recommends determining the underlying cause of secondary hyperparathyroidism, including chronic kidney disease, vitamin D deficiency, or post-bariatric surgery malabsorption 3, 4

Medullary thyroid cancer screening involves basal serum calcitonin and serum CEA measurement, as recommended by the American Thyroid Association 5
Genetic hypophosphatemic disorders, such as X-linked hypophosphatemia, require plasma intact FGF23 measurement and genetic testing, as stated by the National Institutes of Health 6
The Endocrine Society recommends avoiding pitfalls such as assuming "low PTH" means hypoparathyroidism, starting aggressive vitamin D supplementation in primary hyperparathyroidism, or confusing primary with secondary hyperparathyroidism 1, 2, 3

The measurement of serum electrolytes, including sodium, potassium, and bicarbonate, is essential to assess for metabolic abnormalities in patients with suspected hyperparathyroidism 7
Serum uric acid may be elevated in primary hyperparathyroidism, and urinalysis can help assess pH and identify crystals 7
A 24-hour urine collection can measure calcium, creatinine, and volume to assess urinary calcium excretion and stone risk in patients with suspected primary hyperparathyroidism 7
Stone analysis and imaging to quantify stone burden can help assess for nephrolithiasis or nephrocalcinosis in patients with primary hyperparathyroidism 7

The National Kidney Foundation recommends measuring serum calcium, phosphorus, PTH, and 25-OH vitamin D levels regularly in patients with CKD stages 3-5 8
Parathyroidectomy should be considered when persistent serum intact PTH >800 pg/mL is associated with hypercalcemia and/or hyperphosphatemia refractory to medical therapy, according to the American Journal of Kidney Diseases 8
The Kidney Disease: Improving Global Outcomes (KDIGO) guideline suggests that PTH levels between 100-500 pg/mL in CKD patients have insufficient sensitivity and specificity to reliably predict bone disease, although this specific fact is not directly cited, a similar recommendation is made by 9