Thyroid Stimulating Hormone In Serum

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Contents 1 Reference-interval 2 Principle 3 Clinical-significance 4 Increases 5 Decreases 6 Specimen 7 More General Terms 8 Additional Terms 9 References

Reference-interval

• 0.46 to 4.98 uIU/mL
• < 2.5 uIU/mL in 1st trimester of pregnancy [4]

Principle

• The IMx hTSH assay is based on the Microparticle Enzyme Immunoassay (MEIA) technology. The reagents are added to the reaction cell in the following sequence:

• The probe/ electrode assembly delivers the sample & Anti-hTSH Coated Microparticles to the incubation well of the reaction cell.
• The hTSH binds to the Anti-hTSH Coated Microparticles forming an antibody- antigen complex.
• An aliquot of the reaction mixture containing the antibody- antigen complex bound to the microparticles is transferred to the glass fiber matrix. The microparticles bind irreversibly to the glass fiber matrix.
• The matrix is washed to remove unbound materials.
• The Anti-hTSH: Alkaline Phosphatase is dispensed onto the matrix & binds with the antibody- antigen complex.
• The matrix is washed to remove unbound materials.
• The substrate, 4-Methyllumbelliferyl Phosphate, is added to the matrix & the fluorescent product is measured by the MEIA optical assembly.

Clinical-significance

• serum TSH is a screening tool.
• for diagnostic purposes, the serum TSH results should be used in conjunction with other data e.g., symptoms, results of other thyroid tests, clinical impressions, etc.
• in women, high or low normal serum TSH may be harbinger of hypothyroidsim or hyperthyroidism, respectively [5]
• in men, high normal serum TSH may be harbinger of hypothyroidsim [5]

Increases

• primary hypothyroidism
• inadequate thyroid hormone replacement in a patient with hypothyroidism
• TSH- secreting tumor (rare)

Decreases

• hyperthyroidism
• pituitary insufficiency
• hypothalamic insufficiency (rare)

Specimen

• Serum specimens & plasma ( heparin or EDTA) may be used.
• If the assay is to be performed within 24 hours after collection, the specimen should be stored in the refrigerator at 2-8 C. If the testing will be delayed more than 24 hours, the specimen should be frozen. Mix thoroughly after thawing to ensure consistency in the results. Avoid repeated freezing & thawing.
• Specimens showing particulate matter , erythrocytes, or turbidity should be centrifuged before testing.
  

• SAMPLE : 150 uL of specimen is the minimum volume require to perform the assay.

More General Terms

• special chemistry test
• thyroid function test

Additional Terms

• thyroid-stimulating hormone (TSH) or thyrotropin
• thyroxine [T4] (free) in serum
• thyroxine [T4] (total) in serum

References

1. Abbott Laboratories ,Diagnostic Division ,Abbott Park, IL 60064 Thyroid function, IMx TSH, AUGUST 1990.
2. IMx System Operation Manual, Abbott Diagnostics, a Division of Abbott Laboratories, Abbott Park, IL. 60064, AUGUST 1988.
3. IMx System Assay Manual, Abbott Diagnostics, a Division of Abbott Laboratories, Abbott Park, IL. 60064, AUGUST 1988.
4. Negro R et al. Increased pregnancy loss rate in thyroid antibody negative women with TSH levels between 2.5 and 5.0 in the first trimester of pregnancy. J Clin Endocrinol Metab 2010 Sep; 95:E44 PMID: [1]
5. svold BO et al. Serum TSH within the reference range as a predictor of future hypothyroidism and hyperthyroidism: 11-year follow-up of the HUNT study in Norway. J Clin Endocrinol Metab 2012 Jan; 97:93 PMID: [2]

thyroid-stimulating hormone (TSH) in serum