Order Code
2814
Preferred Specimen
Collect 2 mL of serum. Allow the SST tube to clot upright for at least 30 minutes, then centrifuge within 2 hours of collection. Transfer the separated serum into a plastic transport tube and label clearly as serum. Keep frozen.
If multiple tests are being ordered, provide a separate tube specifically for this test.
Container Type
Serum separator tube
Alternate Specimen Requirements
- 2 mL serum from a plain red-top tube: Let the sample clot upright for at least 60 minutes, then centrifuge and transfer the serum to a plastic transport tube within 2 hours of collection. Label as serum from a plain red-top tube and freeze.
- 2 mL EDTA plasma: Centrifuge promptly and separate plasma from cells. Transfer the plasma into a plastic transport tube, label as EDTA plasma, and freeze. If more than one test is ordered, submit a separate tube for this.
Minimum Volume
- 0.5 mL serum or EDTA plasma
Transport Temperature
Frozen
Expected Turnaround Time
2 days
Specimen Stability
Stable for up to 12 hours at room temperature, 3 days refrigerated, or 6 months when frozen.
Methodology
Roche COBAS Electrochemiluminescent Immunoassay (ECLIA) — calibration traceable to NIBSC (95/646) WHO standards.
Rejection Criteria:
Samples exhibiting hemolysis will be rejected.
Overview
Parathyroid hormone (PTH) is secreted by the chief cells of the four parathyroid glands located behind the thyroid gland and plays a key role in calcium regulation. Its secretion follows a negative feedback mechanism, meaning PTH is released when serum ionized calcium levels drop.
PTH maintains calcium balance by:
- Stimulating renal tubular calcium reabsorption and bone resorption
- Promoting vitamin D synthesis in the kidneys to enhance intestinal calcium absorption
- Reducing phosphate reabsorption in the proximal renal tubules, which increases phosphate excretion
Overall, these processes raise both ionized and total serum calcium levels while lowering phosphorus. PTH is also essential for normal bone remodeling, replacing old bone with stronger, new bone.
The hormone is synthesized as a 118–amino acid polypeptide, later processed into its active 84–amino acid form (PTH 1–84), which circulates with a short half-life of about two to five minutes. Circulating fragments, mainly C-terminal portions, are more abundant and persist longer.
Most laboratories use the intact PTH assay, which measures the whole molecule (PTH 1–84) along with larger C-terminal fragments (7–84). Newer assays detect only the whole (bioactive) PTH molecule and may offer greater accuracy in patients with renal failure.
Clinical Significance
PTH testing is used to:
- Evaluate parathyroid gland function
- Investigate causes of hypercalcemia, distinguishing between parathyroid and non-parathyroid origins
- Diagnose and differentiate primary, secondary, and tertiary hyperparathyroidism
- Diagnose hypoparathyroidism
- Monitor treatment response for parathyroid-related conditions
- Assess renal failure patients for possible renal osteodystrophy
- Confirm effective gland removal during parathyroid surgery
Additional Information
PTH testing is used to:
Hyperparathyroidism causes increased calcium, decreased phosphorus, and elevated urinary calcium and phosphate. Long-term effects include renal stones, dehydration, osteoporosis, gastrointestinal issues, and neuromuscular symptoms—often summarized as:
- “Painful bones, renal stones, abdominal groans, and psychic moans.”
Types of Hyperparathyroidism:
- Primary: Caused by benign adenoma or hyperplasia; rarely by carcinoma
- Secondary: Due to chronic hypocalcemia or hyperphosphatemia, often from renal failure
- Tertiary: Results from long-standing secondary hyperparathyroidism leading to autonomous secretion
Hypoparathyroidism is much less common and typically follows thyroid surgery or autoimmune damage. Symptoms include muscle cramps, weakness, tetany, or soft tissue calcifications.
Bone metabolism effects of PTH can be assessed using bone formation markers (e.g., P1NP, osteocalcin, bone-specific alkaline phosphatase) and resorption markers (e.g., C-telopeptide [CTX]).
Interpretative Information
| Condition | PTH | Calcium |
|---|---|---|
| Normal | Normal | Normal |
| Hypoparathyroidism / Secondary Hypocalcemia | Low | Low |
| Mild Hyperparathyroidism / Vitamin D Deficiency | High | Normal |
| Primary Hyperparathyroidism | Normal or High | High |
| Secondary Hyperparathyroidism (CKD, Vit D deficiency) | High | Normal or Low |
| Tertiary Hyperparathyroidism (post-CKD) | High | High |
| Non-Parathyroid Hypercalcemia (malignancy, etc.) | Low | High |
Limitations
- Reference ranges vary between populations and locations.
- Certain medications may raise PTH (e.g., anticonvulsants, lithium, rifampin, steroids, tenofovir).
- Levothyroxine may lower PTH levels.
- Renal failure can cause accumulation of C-terminal fragments—third-generation assays measuring only PTH (1–84) are more accurate.
- Low magnesium can suppress PTH release and mimic hypoparathyroidism.
- Seasonal changes in PTH may occur due to variations in vitamin D levels.
- Previous exposure to mouse monoclonal antibodies may interfere with test accuracy.
References
Bilezikian JP. Hypoparathyroidism. J Clin Endocrinol Metab. 2020;105(6):1722–36.
Bilezikian JP. Primary Hyperparathyroidism. J Clin Endocrinol Metab. 2018;103(11):3993–4004.
Bilezikian JP et al. Guidelines for the Management of Asymptomatic Primary Hyperparathyroidism. J Clin Endocrinol Metab. 2014;99(10):3561–9.
Brandi ML et al. Management of Hypoparathyroidism: Summary Statement and Guidelines. J Clin Endocrinol Metab. 2016;101(6):2273–83.
Chen H et al. Parathyroid Hormone Fragments: New Targets for Diagnosis and Treatment of CKD-MBD. Biomed Res Int. 2018;2018:9619253.
Fuleihan GE, Juppner H. Parathyroid Hormone Assays and Their Clinical Use. UpToDate. 2021.
Mannstadt M. Parathyroid Hormone Secretion and Action. UpToDate. 2021.
Galarza JB. Thyroid Function Tests. In: Farwell A, ed. Clinical Thyroidology for the Public. Falls Church, VA: American Thyroid Association; 2018.
Hanon EA, Sturgeon CM, Lamb EJ. Sampling and Storage Conditions Influencing the Measurement of Parathyroid Hormone in Blood Samples: A Systematic Review. Clin Chem Lab Med. 2013;51(10):1925–1941.
LabTestsOnLine. Parathyroid Hormone (PTH).https://labtestsonline.org/tests/parathyroid-hormone-pth. Updated March 24, 2021.
Li D, Ferguson A, Cervinski MA, Lynch KL, Kyle PB. AACC Guidance Document on Biotin Interference in Laboratory Tests. J Appl Lab Med. 2020 May;5(3):575–587. doi: 10.1093/jalm/jfz010.
Losartan and Hydrochlorothiazide. Lexi-Drugs. UpToDate Lexidrug. Accessed September 27, 2021.
Mannstadt M. Parathyroid Hormone Secretion and Action. UpToDate. Waltham, MA: UpToDate Inc. Accessed September 2, 2021.
Naramala S, Dalal H, Adapa S, Hassan A, Konala VM. Lithium-Induced Hyperparathyroidism and Hypercalcemia. Cureus. 2019 May;11(5):e4590. doi: 10.7759/cureus.4590.
RIFADIN (rifampin) [Prescribing Information]. Bridgewater, NJ: Sanofi-Aventis US; June 2021.
Saizen (somatropin) [Prescribing Information]. Rockland, MA: EMD Serono Inc; February 2020.
Smit MA, van Kinschot CMJ, van der Linden J, van Noord C, Kos S. Clinical Guidelines and PTH Measurement: Does Assay Generation Matter? Endocr Rev. 2019 Dec;40(6):1468–1480.
Sturgeon CM, Sprague S, Almond A, et al. Perspective and Priorities for Improvement of Parathyroid Hormone (PTH) Measurement. Clin Chim Acta. 2017 Apr;467:42–47.
Tirosint-SOL (levothyroxine) [Prescribing Information]. Parsippany, NJ: IBSA Pharma Inc; January 2021.
US Food & Drug Administration (FDA). UPDATE: The FDA Warns that Biotin May Interfere with Lab Tests. November 5, 2019. Accessed September 7, 2021.
VIREAD (tenofovir disoproxil fumarate) [Prescribing Information]. Foster City, CA: Gilead Sciences, Inc; April 2019.
Walker MD, Silverberg SJ. Primary Hyperparathyroidism. Nat Rev Endocrinol. 2018 Feb;14(2):115–125. doi: 10.1038/nrendo.2017.104.
Wilhelm SM, Wang TS, Ruan DT, Lee JA, Asa SL, Duh QY, Doherty GM, Herrera MF, Pasieka JL, Perrier ND, Silverberg SJ, Solórzano CC, Sturgeon C, Tublin ME, Udelsman R, Carty SE. The American Association of Endocrine Surgeons Guidelines for Definitive Management of Primary Hyperparathyroidism. JAMA Surg. 2016 Oct;151(10):959–968.
Diagnostic Role
PTH testing is commonly ordered after detecting an elevated calcium level in routine lab work or during evaluation for other conditions. Symptoms that may prompt calcium and PTH testing include nausea, vomiting, confusion, kidney stones (hypercalcemia), or muscle cramps and tingling sensations (hypocalcemia).
Results should be interpreted alongside calcium and phosphorus levels, as well as the patient’s clinical presentation and medical history.
Alias
pth, intact
Test Setup Days
Monday through Friday PM shift
CPT
83970 LOINC: 2731-8
Reference Range
15-65 PG/ML
| UNIT CODE | UNIT CODE NAME | ANALYTE | GENDER | AGE | REFERENCE RANGE | Units of Measure |
|---|---|---|---|---|---|---|
| 2814 | INTACT PTH | PTHINT | NOT SPECIFIED | ALL | 15–65 | PG/ML |
| 2814 | INTACT PTH | PTHINT | MALE | ALL | 15–65 | PG/ML |
| 2814 | INTACT PTH | PTHINT | FEMALE | ALL | 15–65 | PG/ML |