Hypoparathyroidism laboratory findings: Difference between revisions
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{{Hypoparathyroidism}} | {{Hypoparathyroidism}} | ||
{{CMG}}; {{AE | {{CMG}}; {{AE}} | ||
==Overview== | ==Overview== | ||
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==Laboratory Findings== | ==Laboratory Findings== | ||
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==Laboratory Findings== | ==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.<ref name="pmid18650515">{{cite journal |vauthors=Shoback D |title=Clinical practice. Hypoparathyroidism |journal=N. Engl. J. Med. |volume=359 |issue=4 |pages=391–403 |year=2008 |pmid=18650515 |doi=10.1056/NEJMcp0803050 |url=}}</ref> | |||
*[[PTH]] degrades rapidly at ambient temperatures and the blood sample therefore has to be transported to the laboratory on ice. | |||
*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. | *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. | *Hypomagnesemia and vitamin D deficiency should be ruled out as cause of hypocalcemia before making a diagnosis of hypoparathyroidism. | ||
*Calculation of corrected total calcium: | *Calculation of corrected total calcium: | ||
<div style="text-align: center;">'''Corrected total calcium = measured total calcium + 0.8 (4.0 − serum albumin)''' </div style> | <div style="text-align: center;">'''Corrected total calcium = measured total calcium + 0.8 (4.0 − serum albumin)''' </div style> | ||
:*In this formula, serum calcium is measured in mg/dL and serum albumin is measured in gm/dL. | |||
*Laboratory findings consistent with the diagnosis of hypoparathyroidism include: | *Laboratory findings consistent with the diagnosis of hypoparathyroidism include: | ||
**Low parathyroid hormone | **Low parathyroid hormone | ||
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<br> | <br> | ||
{| | {| | ||
! Disorder | ! style="background: #4479BA; text-align: center;" |{{fontcolor|#FFF|Disorder}} | ||
! | ! rowspan="2" style="background: #4479BA; text-align: center;" |{{fontcolor|#FFF|Hypoparathyroidism}} | ||
! | ! rowspan="2" style="background: #4479BA; text-align: center;" |{{fontcolor|#FFF|Classic vitamin D deficiency}} | ||
! | ! rowspan="2" style="background: #4479BA; text-align: center;" |{{fontcolor|#FFF|Pseudohypoparathyroidism}} | ||
! rowspan="2" style="background: #4479BA; text-align: center;" |{{fontcolor|#FFF|Hypomagnesemia}} | |||
|- | |- | ||
| | ! style="background: #7d7d7d; text-align: center;" |{{fontcolor|#FFF|Laboratory findings}} | ||
| | |||
| | |||
|- | |- | ||
| | | style="background: #F0FFFF; text-align: center;" |Serum calcium concentration | ||
| ↓ | | style="background: #DCDCDC; text-align: center;" | ↓ | ||
| | | style="background: #DCDCDC; text-align: center;" | ↓ | ||
| ↓ | | style="background: #DCDCDC; text-align: center;" | ↓ | ||
| style="background: #DCDCDC; text-align: center;" | Slightly ↓ | |||
|- | |- | ||
| | | style="background: #F0FFFF; text-align: center;" |Intact PTH | ||
| ↓ | | style="background: #DCDCDC; text-align: center;" | ↓ | ||
| ↑ | | style="background: #DCDCDC; text-align: center;" | ↑ | ||
| ↑ | | style="background: #DCDCDC; text-align: center;" | ↑ | ||
| style="background: #DCDCDC; text-align: center;" | Inappropriately ↓ | |||
|- | |||
| style="background: #F0FFFF; text-align: center;" |Serum phosphate concentration | |||
| style="background: #DCDCDC; text-align: center;" | ↑ | |||
| style="background: #DCDCDC; text-align: center;" | ↓/Low-normal | |||
| style="background: #DCDCDC; text-align: center;" | ↑ | |||
| style="background: #DCDCDC; text-align: center;" | -- | |||
|} | |} | ||
If necessary, measuring [[Cyclic adenosine monophosphate|cAMP]] ([[cyclic AMP]]) in the urine after an intravenous dose of [[PTH]] can help in the distinction between [[hypoparathyroidism]] and other causes. | |||
==Biochemical Tests== | |||
===Serum Calcium=== | |||
*Measurement of total serum [[calcium]] with automatic techniques has similar or even more reliability than serum ionized [[calcium]] measurement. | |||
===Serum Parathyroid Hormone=== | |||
*Method of choice for measuring intact parathyroid hormone include Immunoradiometric assay (IMRA) or Immunochemiluminescent assay (ICMA).<ref name="pmid1993319">{{cite journal |vauthors=Endres DB, Villanueva R, Sharp CF, Singer FR |title=Immunochemiluminometric and immunoradiometric determinations of intact and total immunoreactive parathyrin: performance in the differential diagnosis of hypercalcemia and hypoparathyroidism |journal=Clin. Chem. |volume=37 |issue=2 |pages=162–8 |year=1991 |pmid=1993319 |doi= |url=http://clinchem.aaccjnls.org/content/clinchem/37/2/162.full.pdf}}</ref> | |||
===24-Hour Urinary Calcium=== | |||
*24-Hour urinary calcium excretion is indicated by the urinary calcium:creatinine clearance ratio. | |||
*Hypoparathyroidism and vitamin D deficiency have low urinary calcium excretion. | |||
*Hypocalcemic patients with activating mutations in the extracellular calcium-sensing receptor have a subtantially higher urinary calcium:creatinine clearance ratio.<ref name="pmid11134112">{{cite journal |vauthors=Yamamoto M, Akatsu T, Nagase T, Ogata E |title=Comparison of hypocalcemic hypercalciuria between patients with idiopathic hypoparathyroidism and those with gain-of-function mutations in the calcium-sensing receptor: is it possible to differentiate the two disorders? |journal=J. Clin. Endocrinol. Metab. |volume=85 |issue=12 |pages=4583–91 |year=2000 |pmid=11134112 |doi=10.1210/jcem.85.12.7035 |url=}}</ref> | |||
===Serum Magnesium=== | |||
*Serum magnesium concentration should be measured to rule out hypomagnesemia (or sometimes hypermagnesemia) as a cause of hypocalcemia. | |||
*Hypomagesemia as a contributor to hypocalcemia may be difficult to rule out as serum magnesium levels may be normal even if there depletion of intracellular magnesium stores. | |||
*Serum magnesium decreases to subnormal levels as magnesium depletion progresses. | |||
*Elevated or even detectable urinary levels of magnesium suggest magnesium depletion due to renal losses since kidney should conserve magnesium in depleted body stores. | |||
===24-Hour Urinary Magnesium=== | |||
24-hour urinary magnesium level measurement before initiation of treatment is useful, if magnesium deficiency is detected as a cause of hypocamcemia. | |||
===Serum 25-Hydroxy Vitamin D=== | |||
*Serum 25-Hydroxy Vitamin D should be measured to rule out vitamin D deficiency as a cause of hypocalcemia. | |||
==References== | ==References== |
Revision as of 14:51, 22 September 2017
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:
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
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.[1]
- PTH degrades rapidly at ambient temperatures and the blood sample therefore has to be transported to the laboratory on ice.
- 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:
- In this formula, serum calcium is measured in mg/dL and serum albumin is measured in gm/dL.
- 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 | Hypoparathyroidism | Classic vitamin D deficiency | Pseudohypoparathyroidism | Hypomagnesemia |
---|---|---|---|---|
Laboratory findings | ||||
Serum calcium concentration | ↓ | ↓ | ↓ | Slightly ↓ |
Intact PTH | ↓ | ↑ | ↑ | Inappropriately ↓ |
Serum phosphate concentration | ↑ | ↓/Low-normal | ↑ | -- |
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.
Biochemical Tests
Serum Calcium
- Measurement of total serum calcium with automatic techniques has similar or even more reliability than serum ionized calcium measurement.
Serum Parathyroid Hormone
- Method of choice for measuring intact parathyroid hormone include Immunoradiometric assay (IMRA) or Immunochemiluminescent assay (ICMA).[2]
24-Hour Urinary Calcium
- 24-Hour urinary calcium excretion is indicated by the urinary calcium:creatinine clearance ratio.
- Hypoparathyroidism and vitamin D deficiency have low urinary calcium excretion.
- Hypocalcemic patients with activating mutations in the extracellular calcium-sensing receptor have a subtantially higher urinary calcium:creatinine clearance ratio.[3]
Serum Magnesium
- Serum magnesium concentration should be measured to rule out hypomagnesemia (or sometimes hypermagnesemia) as a cause of hypocalcemia.
- Hypomagesemia as a contributor to hypocalcemia may be difficult to rule out as serum magnesium levels may be normal even if there depletion of intracellular magnesium stores.
- Serum magnesium decreases to subnormal levels as magnesium depletion progresses.
- Elevated or even detectable urinary levels of magnesium suggest magnesium depletion due to renal losses since kidney should conserve magnesium in depleted body stores.
24-Hour Urinary Magnesium
24-hour urinary magnesium level measurement before initiation of treatment is useful, if magnesium deficiency is detected as a cause of hypocamcemia.
Serum 25-Hydroxy Vitamin D
- Serum 25-Hydroxy Vitamin D should be measured to rule out vitamin D deficiency as a cause of hypocalcemia.
References
- ↑ Shoback D (2008). "Clinical practice. Hypoparathyroidism". N. Engl. J. Med. 359 (4): 391–403. doi:10.1056/NEJMcp0803050. PMID 18650515.
- ↑ Endres DB, Villanueva R, Sharp CF, Singer FR (1991). "Immunochemiluminometric and immunoradiometric determinations of intact and total immunoreactive parathyrin: performance in the differential diagnosis of hypercalcemia and hypoparathyroidism" (PDF). Clin. Chem. 37 (2): 162–8. PMID 1993319.
- ↑ Yamamoto M, Akatsu T, Nagase T, Ogata E (2000). "Comparison of hypocalcemic hypercalciuria between patients with idiopathic hypoparathyroidism and those with gain-of-function mutations in the calcium-sensing receptor: is it possible to differentiate the two disorders?". J. Clin. Endocrinol. Metab. 85 (12): 4583–91. doi:10.1210/jcem.85.12.7035. PMID 11134112.