Hypoparathyroidism laboratory findings

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Omodamola Aje B.Sc, M.D. [2]

Overview

An elevated/reduced concentration of serum/blood/urinary/CSF/other [lab test] is diagnostic of [disease name].

OR

Laboratory findings consistent with the diagnosis of [disease name] include [abnormal test 1], [abnormal test 2], and [abnormal test 3].

OR

[Test] is usually normal among patients with [disease name].

OR

Some patients with [disease name] may have elevated/reduced concentration of [test], which is usually suggestive of [progression/complication].

OR

There are no diagnostic laboratory findings associated with [disease name].

Laboratory Findings

Diagnosis of hypoparathyroidism is made by measurement of serum calcium (total and ionized), serum albumin (for correction), phosphate, intact Parathyroid hormone (PTH), and 25-hydroxyvitamin D (25[OH] vitamin D) levels. PTH degrades rapidly at ambient temperatures and the blood sample therefore has to be transported to the laboratory on ice.

If necessary, measuring cAMP (cyclic AMP) in the urine after an intravenous dose of PTH can help in the distinction between hypoparathyroidism and other causes.

In this formula, serum calcium is measured in mg/dL and serum albumin is measured in gm/dL.

Laboratory Findings

• Normal or inappropriately low serum intact parathyroid hormone (PTH) concentration in patients with subnormal serum albumin corrected total or ionized calcium concentration diagnostic of hypoparathyroidism.
• Hypomagnesemia and vitamin D deficiency should be ruled out as cause of hypocalcemia before making a diagnosis of hypoparathyroidism.
• Calculation of corrected total calcium:

Corrected total calcium = measured total calcium + 0.8 (4.0 − serum albumin)

• Laboratory findings consistent with the diagnosis of hypoparathyroidism include:
  • Low parathyroid hormone
  • Low serum calcium level
  • Normal to elevated serum phosphate concentration

• Some patients with [disease name] may have elevated/reduced concentration of [test], which is usually suggestive of [progression/complication].

Disorder	Serum calcium concentration	Intact PTH	Serum phosphate concentration
Hypoparathyroidism	↓	↓	↑
Classic vitamin D deficiency	↓	↑	↓/Low-normal
Pseudohypoparathyroidism	↓	↑	↑