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PTH, Intact and Calcium

Test code(s) 8837

This test is used to do the following:

  • Diagnose and monitor hypo- and hyperparathyroidism
  • Differentiate primary hyperparathyroidism from hypercalcemia of malignancy

Intact Parathyroid hormone (PTH) is the biologically active form of PTH. It acts to increase circulating calcium, decrease circulating phosphorous, and increase the active form of vitamin D [1,25(OH)2D], by mobilizing calcium from bone and retaining calcium in the kidneys.

Results observed in various conditions follow1:

Table: Interpretation of parathyroid hormone (PTH) and calcium test results

No patient preparation is required.

Please visit the Quest Diagnostics Test Directory for up-to-date information on preferred and alternative specimen:    

Heterophile antibodies (antibodies to animal immunoglobulins), which are rarely present in blood, could cause anomalous results.

Parathyroid hormone (PTH) values vary from one method to the next. You can compare values generated by different methods by comparing where each result falls within the respective method’s reference range. Calcium values may vary among methods as well and can be compared in the same manner. 


  1. Kaplan LA, Pesce AJ, eds. Clinical chemistry: Theory, analysis, correlation. St. Louis, MO: Mosby Elsevier;2010: 638-643.
  2. Smit MA, van Kinschot CMJ, van der Linden J, et al. Clinical guidelines and PTH measurement: Does assay generation matter? Endocr Rev. 2019;40(6):1468-1480. doi:10.1210/er.2018-00220


This FAQ is provided for informational purposes only and is not intended as medical advice. Test selection and interpretation, diagnosis, and patient management decisions should be based on the physician’s education, clinical expertise, and assessment of the patient.


Document FAQS.131 Version: 1

Version 1 effective 05/30/2023 to present

Version 0 effective 12/13/2013 to 05/30/2023