Canis ISSN: 2398-2942

Thyroid: TSH assay

Synonym(s): Thyroid stimulating hormone assay

Contributor(s): David Bruyette, Roger Powell

Overview

  • Thyrotropin releasing hormone (TRH, from the hypothalamus) stimulates production of TSH from the anterior pituitary to regulate the synthesis and secretion of thyroxine (T4) and tri-iodothyronine (T3)  Hypothalamic-pituitary-thyroid axis diagram. This is a negative feedback system, the released (free) T4 and T3 inhibiting further release of TSH.

Sampling

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Tests

Methodologies

  • Requires canine specific or validated assays.
  • Varied Fluorescent and Enzymatic ImmunoAssays (EIAs) Enzyme linked immunosorbent assay (ELISA) or RadioImmunological Assays (RIAs).
  • Laboratory testing should use external quality assurance schemes to validate performance, eg VEEEQAS / ESVE.

Availability

  • Most commercial laboratories (EIAs), few reference laboratories (RIAs).

Validity

  • Varies with study, test methodology and reference method used, historically often relative to dynamic TSH stimulation testing or thyroid gland histopathology.

Sensitivity

  • 75-87%.

Specificity

  • 82-100%. 
  • 10-20% sick-euthyroid dogs have increased TSH.

Predictive value

  • Positive predictive value 55-75% (depending on test and which group of dogs are being tested).
  • Negative predictive value 90-100% (depending on test and which group of dogs are being tested.

Technique (intrinsic) limitations

  • Cannot accurately distinguish low and normal concentrations of cTSH.

Technician (extrinsic) limitations

  • Minimal risk of technician errors.

Result Data

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Further Reading

Publications

Refereed papers

  • Recent references from VetMedResource and PubMed.
  • Dixon R M &Mooney C T (1999) Evaluation of serum free thyroxine and thyrotropin concentrations in the diagnosis of canine hypothyroidism. JSAP 40(2), 72-78.
  • Panclera D L (1999)Is it possible to diagnose hypothyroidism? JSAP 40(4), 152-157.
  • Iversen L, Hoier R, Jensen A L et al(1998) Evaluation of the analytical performance of an enzyme immunometric assay (EIA) designed to measure endogenous thyroid-stimulating hormone (TSH) in canine serum samples. JAVMA 45, 93-98.
  • Bruner J M, Scott-Moncrieff C R & Williams D A (1998) Effect of time of sample collection on serum thyroid-stimulating hormone concentrations in euthyroid and hypothyroid dogs. JAVMA 212, 1572-1575.
  • Peterson M E, Melian C & Nichols R (1997) Measurement of serum total thyroxine, triodothyronine, free thyroxine and thyrotropin concentrations for diagnosis of hypothyroidism in dogs. JAVMA 211, 1396-1402.
  • Ramsey I K, Evans H & Herrtage M E (1997) Thyroid stimulating hormone and total thyroxine concentrations in euthyroid, sick euthyroid and hypothyroid dogs. JSAP 38(12), 540-545.
  • Dixon R M, Graham P A & Mooney C T (1996) Serum thyrotropin concentrations - a new diagnostic test for canine hypothyroidism. Vet Rec 138, 594-595.

Other sources of information

  • Information available from commercial laboratories who perform the test.


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