Parathyroid Hyperfunction (Hyperparathyroidism): Test and Diagnosis

1st order laboratory parameters – obligatory laboratory tests.

Confirming the diagnosis of primary hyperparathyroidism.

• Intact (1-84) parathyroid hormone (PTH) [↑]
• Electrolytes
  • Calcium – in serum and urine (24-hour urine) [↑; hypercalcemia (calcium excess)]
  • Inorganic phosphate [in serum ↓; in urine ↑]
• Total protein in serum
• To investigate renal damage:
  • Creatinine in serum
  • Urea
• Serum potassium
• In case of bone involvement:
  • Alkaline phosphatase [↑]
  • Hydroxyproline excretion [↑]

Primary hyperparathyroidism is likely (> 95%) if there is an elevation of serum calcium > 2.6 mmol/l (with normal renal function and normal total protein), confirmed by at least three determinations on different days, and elevated PTH intact.

If there is concomitant vitamin D deficiency, renal insufficiency, or albumin deficiency, normocalcemic primary hyperparathyroidism may be present.

Serum calcium and serum creatinine should be monitored annually as part of conservative therapy.

Secondary hyperparathyroidism

• Intact (1-84) parathyroid hormone (PTH) [↑]
• Electrolytes
  • Calcium – in serum and urine (24-hour urine) [in serum ↓; in urine ↑ or even normal].
  • Inorganic phosphate – [in serum ↓; in urine ↓]
• 25-OH vitamin D [↓]
• In renal insufficiency:
  • Intact (1-84) parathyroid hormone (PTH) [↑]
  • Electrolytes
    • Calcium [↓]
    • Inorganic phosphate [↑]
  • Renal parameters – urea, creatinine [↑]
  • Glomerular filtration rate (GFR) [↓]

Tertiary hyperparathyroidism

• Intact (1-84) parathyroid hormone (PTH) [↑]
• Electrolytes
  • Calcium [in serum ↑; in urine ↓]
  • Inorganic phosphate [in serum ↑; in urine ↓]

Differential diagnosis of hyperparathyroidism