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An immunoglobulin G complexed form of thyroid-stimulating hormone (macro thyroid-stimulating hormone) is a cause of

Francesca Mills1, Jinny Jeffery, Paul Mackenzie

  • 1Department of Clinical Biochemistry, Derriford Hospital, Plymouth, UK. francesca.mills@nhs.net

Annals of Clinical Biochemistry
|July 6, 2013
PubMed

Insights

Macro-thyroid-stimulating hormone (TSH) can elevate TSH levels, causing diagnostic confusion. A study found macro-TSH in 0.6% of samples, highlighting the need for awareness in clinical laboratories.

Area of Science:

  • Clinical Chemistry
  • Endocrinology
  • Laboratory Medicine

Background:

  • Macrocomplexes can cause elevated serum hormone concentrations, leading to diagnostic confusion.
  • Polyethylene glycol (PEG) precipitation is a common screening method for macroprolactin, but less familiar for macro-thyroid-stimulating hormone (TSH).
  • Elevated TSH levels may be misinterpreted without considering the possibility of macro-TSH.

Purpose of the Study:

  • To determine the prevalence of macro-TSH in routine thyroid function testing.
  • To establish a screening method for macro-TSH in the Roche Elecsys assay.
  • To alert laboratories to macro-TSH as a potential cause of assay interference.

Main Methods:

  • Samples with TSH >10 mU/L were analyzed for macro-TSH using the Roche Elecsys assay.
  • Polyethylene glycol (PEG) precipitation was employed as a screening method.
  • Gel filtration chromatography was used for confirmation of macro-TSH.

Main Results:

  • Out of 495 samples tested, 3 (0.6%) exhibited macro-TSH.
  • A PEG precipitation recovery cut-off of <25% was identified for detecting samples with macro-TSH.
  • The study confirmed macro-TSH as a cause of elevated TSH concentrations.

Conclusions:

  • The prevalence of elevated TSH due to macro-TSH is 0.6%.
  • Laboratories should be aware of macro-TSH as a cause of assay interference in thyroid function tests.
  • Implementing screening methods for macro-TSH is recommended for accurate TSH measurement.
Abstract

Keywords:
Thyroid hormonesanalytesclinical studiesimmunoassaylaboratory methodsthyroid disease

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