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J Clin Endocrinol Metab. 2010 May;95(5):2123-31. doi: 10.1210/jc.2009-2470. Epub 2010 Mar 17.

A novel thyroid stimulating immunoglobulin bioassay is a functional indicator of activity and severity of Graves' orbitopathy.

Author information

1
Department of Medicine I, Gutenberg University Medical Center, Mainz 55101, Germany.

Abstract

CONTEXT:

Immunoglobulins stimulating the TSH receptor (TSI) influence thyroid function and likely mediate extrathyroidal manifestations of Graves' disease (GD).

OBJECTIVES:

The aim of this study was to assess the clinical relevance of TSI in GD patients with or without Graves' orbitopathy (GO), to correlate the TSI levels with activity/severity of GO, and to compare the sensitivity/specificity of a novel TSI bioassay with TSH receptor (TSH-R) binding methods (TRAb).

DESIGN:

TSI were tested in two reporter cell lines designed to measure Igs binding the TSH-R and transmitting signals for cAMP/CREB/cAMP regulatory element complex-dependent activation of luciferase gene expression. Responsiveness to TSI of the novel chimeric (Mc4) TSH-R (amino acid residues 262-335 of human TSH-R replaced by rat LH-R) was compared with the wild-type (wt) TSH-R.

RESULTS:

All hyperthyroid GD/GO patients were TSI-positive. TSI were detected in 150 of 155 (97%, Mc4) and 148 of 155 (95%, wt) GO patients, in six of 45 (13%, Mc4) and 20 of 45 (44%, wt) mostly treated GD subjects, and in 0 of 40 (Mc4) and one of 40 (wt) controls. Serum TSI titers were 3- and 8-fold higher in GO vs. GD and control, respectively. All patients with diplopia and optic neuropathy and smokers were TSI-positive. TSI strongly correlated with GO activity (r = 0.87 and r = 0.7; both P < 0.001) and severity (r = 0.87 and r = 0.72; both P < 0.001) in the Mc4 and wt bioassays, respectively. Clinical sensitivity (97 vs. 77%; P < 0.001) and specificity (89 vs. 43%; P < 0.001) of the Mc4/TSI were greater than TRAb in GO. All 11 of 200 (5.5%) TSI-positive/TRAb-negative patients had GO, whereas all seven of 200 (3.5%) TSI-negative/TRAb-positive subjects had GD only.

CONCLUSION:

The novel Mc4/TSI is a functional indicator of GO activity and severity.

PMID:
20237164
DOI:
10.1210/jc.2009-2470
[Indexed for MEDLINE]

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