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Changes to Cheltenham A&E during BMA Industrial Action 17 - 22 December

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Parathyroid hormone (PTH)

Clinical Biochemistry

Background information

  • Parathyroid hormone (PTH) is secreted by the parathyroid glands and plays an important role in calcium homeostasis.
  • PTH analysis is used in the investigation of abnormal calcium levels, to distinguish between parathyroid and non-parathyroid causes; in monitoring renal patients and in assessing patients immediately post parathyroidectomy (or thyroidectomy).
  • As PTH changes rapidly in response to calcium levels and is also cleared from the blood very quickly (half-life approximately 5 minutes) it is essential to always interpret PTH levels in conjunction with the calcium level. Requests for PTH should therefore always be accompanied by a request for a concurrent calcium level.
  • The local PTH assay measures intact PTH molecule 1-84 amino acids.

PTH can be assayed during a parathyroidectomy on an urgent basis (i.e. intra-operative PTH levels) however this must be booked with the laboratory at least a week in advance. Please contact the duty biochemist for further details if access to this service is required.

Patient preparation

No specific preparation required

Sample requirements

  • Two different sample tube types are required; an EDTA sample for PTH and a plain serum sample for concurrent calcium.
  • Draw Gold/RUST top tubes first as EDTA contamination will cause falsely low calcium levels (please note that if no gold top tube is sent for calcium then PTH will not be assayed).

For adults use a 4mL EDTA tube plus a 5mL gold top gel tube (or rust top for the Acute Unit)

EDTA with cap

5ml gold tube


For children use a 2mL EDTA tube plus a 3.5mL rust top tube

Sample tube: pink cap


3.5ml rust top tube


Storage/transport

Send at ambient temperature to the laboratory.

Required information

Relevant clinical details including current medication.

Turnaround times

The in-lab turnaround time is less than one week.

The test can be ordered as an urgent request.

Reference ranges

1.6 - 6.9 pmol/L when the patient is normocalcaemic.

Note: PTH levels within this range may be inappropriate when calcium levels are outside the adjusted calcium reference range.

Further information

To learn more about PTH visit Lab Tests Online

Page last updated 20/11/2025

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