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Pregnenolone, Mass Spectrometry (Endocrine Sciences)

CPT: 84140
Updated on 12/9/2019
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Expected Turnaround Time

7 - 10 days



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Specimen Requirements


Specimen

Serum (preferred) or plasma, frozen


Volume

2.5 mL


Minimum Volume

1.1 mL (Note: This volume does not allow for repeat testing.)


Container

Red-top tube, gel-barrier tube, lavender-top (EDTA) tube, or green-top (heparin) tube


Collection

Serum or plasma must be separated from cells and transferred to a plastic transport tube within one hour of collection. The specimen should be frozen immediately and maintained frozen until tested. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.


Storage Instructions

Freeze.


Stability Requirements

Temperature

Period

Room temperature

4 hours

Refrigerated

2 days

Frozen

2 years

Freeze/thaw cycles

Stable x3


Patient Preparation

The patient need not be fasting.


Test Details


Limitations

This test was developed and its performance characteristics determined by LabCorp. It has not been cleared or approved by the Food and Drug Administration.


Methodology

Liquid chromatography/tandem mass spectrometry (LC/MS-MS)


Additional Information

In humans, steroid hormones are produced by the adrenal glands and the gonads.1,2 The formation of pregnenolone from cholesterol is the first step in steroidogenesis and is mediated by the proteolytic enzyme, single cholesterol side-chain cleavage enzyme (P450 scc). Steroidogenesis continues along two paths from pregnenolone. 17-Hydroxypregnenolone is produced from pregnenolone through the enzymatic action of 17α-hydroxylase (17α-H). Alternatively, pregnenolone is converted to progesterone through the enzymatic action of 3β-hydroxysteroid dehydrogenase (3β-HSD).

Pregnenolone levels have been shown to remain in the normal range in patients with Cushing syndrome and hyperaldosteronism.3,4 Levels can be suppressed with dexamethasone inhibition and increased with exogenous ACTH stimulation.3 Pregnenolone levels have been shown to be elevated in patients with idiopathic hirsutism.4

Since the various forms of congenital adrenal hyperplasia (CAH) result from enzymatic defects in the adrenal steroidogenic pathways, measurement of pregnenolone levels can be useful in diagnosis. Pregnenolone levels tend to be elevated in several forms of CAH, particularly in 17α-H deficiency and 3β-HSD deficiency since these enzymes catalyze steps immediately after pregnenolone in the steroidogenic pathways.2


Footnotes

1. Demers LM, Whitley R. Function of the adrenal cortex. In: Burtis CA, Ashwood ER, eds. Tietz Textbook of Clinical Chemistry. 3rd ed. Philadelphia, Pa: WB Saunders Co; 1999: 1530-1569.
2. Donohoue PA, Parker K, Migeon CJ. Congenital adrenal hyperplasia. In: Scriver CR, Beaudet AL, Sly WS, et al, eds. The Metabolic and Molecular Bases of Inherited Disease. 1995: 2929-2966.
3. McKenna TJ, Brown RD. Pregnenolone in man: Plasma levels in states of normal and abnormal steroidogenesis. J Clin Endocrinol Metab. 1974; 38(3):480-485. 4360922
4. McKenna TJ, Miller RB, Liddle GW. Plasma pregnenolone and 17-OH-pregnenolone in patients with adrenal tumors, ACTH excess, or idiopathic hirsutism. J Clin Endocrinol Metab. 1977; 44(2):231-236. 190251

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
140707 Pregnenolone, MS 140709 Pregnenolone, MS ng/dL 2837-3

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