Thyroid-stimulating Hormone (TSH)

Alternate Name: TSH3

  | Thyrotropin, TSH 3rd Generation

SAL Code:

705

CPT:

84443

Loinc:

3016-3

Turn Around Time:

1 Day

Setup:

Daily

Units:

uIU/mL

Department:

Endocrinology

Performing Laboratory:

Sherman Abrams Laboratory

Methodology:

Electrochemiluminescence immunoassay (ECLIA)

Specimen Requirements:

Primary Tube:

SST

Primary Substance:

Serum

Alternate Sample Info:

Li-heparin, or K2 orK3 EDTA tubes

Temperature

Period

Stable Ambient:

8 Days

Stable Fridge:

14 Days

Stable Frozen:

30 Days

Rejection Criteria:

Improper labeling

Clinical Info:

This assay has been designed for the quantitative determination of thyrotropin in human serum and plasma. Measurements of TSH may be used in the diagnosis of thyroid and pituitary disorders.

TSH, released from the anterior pituitary, is the principal regulator of thyroid function, stimulating the synthesis and release of thyroid hormones thyroxine (T4) and triiodothyronine (T3). T3 and T4 regulate biochemical processes that are essential for normal metabolism. The synthesis and secretion of TSH is stimulated by thyrotropin-releasing hormone (TRH), which is produced by the hypothalamus in response to low levels of circulating T3 and T4. In contrast, elevated levels of T3 and T4 suppress the production of TSH. Collectively, this negative feedback system is referred to as the hypothalamic-pituitary-thyroid axis. Any alteration in the function of this axis can influence the levels of TSH, T4, and T3 in circulation.

The principal clinical use for TSH measurement is for the assessment of thyroid status. TSH may be measured in conjunction with thyroid hormones or antibodies to detect or exclude hypothyroidism or hyperthyroidism, monitor T4 replacement treatment in hypothyroidism or antithyroid treatment in hyperthyroidism, monitor TSH suppression in thyroid cancer patients on thyroxine therapy, assess the response to TRH stimulation testing and other clinically warranted scenarios.

Reference ranges for TSH may vary, depending on gender, age, and other factors. Please see final laboratory report for reference ranges.

Additional Information:

TSH is formed in specific basophil cells of the anterior pituitary and is subject to a circadian secretion sequence. The hypophyseal release of TSH (thyrotropic hormone) is the central regulating mechanism for the biological action of thyroid hormones. TSH has a stimulating action in all stages of thyroid hormone formation and secretion; it also has a proliferative effect.
The determination of TSH serves as the initial test in thyroid diagnostics. Even very slight changes in the concentrations of the free thyroid hormones bring about much greater opposite changes in the TSH level. Accordingly, TSH is a very sensitive and specific parameter for assessing thyroid function and is particularly suitable for early detection or exclusion of disorders in the central regulating circuit between the hypothalamus, pituitary and thyroid.

Sample Collection:

Collect patient samples using standard phlebotomy techniques. Click here for additional collection instructions.

Test Limitations:

Assay interference may occur in serum with biotin concentrations of greater than 1200 ng/mL. Some studies have shown that serum concentrations of biotin can reach up to 355 ng/mL within the first hour after biotin ingestion for subjects consuming supplements of 20 mg biotin per day and up to 1160 ng/mL for subjects after a single dose of 300 mg biotin.
There is no high-dose hook effect at TSH concentrations up to 1000 µIU/mL.

Test Information:

Components: