A bioluminescence assay for thyrotropin receptor antibodies predicts serum thyroid hormone levels in patients with de novo Graves' disease.
BACKGROUND
TSH receptor antibodies (TBII) in Graves' disease (GD) may be TSH receptor stimulating (TSAb) and blocking (TBAb) antibodies. In commercially available assays however, only total TBII titres can be measured, without discriminating between TSAb and TBAb.


OBJECTIVE
To design a TBII bioassay to detect of TSAb and to correlate TSAb activity with severity of hyperthyroidism in de novo GD patients.


METHODS
Thirty-five patients with de novo GD and 27 controls.


METHODS
The JP-26-26 cell line, which constitutively expresses the TSH receptor (TSHR), was stably transfected with a cyclic adenosine monophosphate responsive element--luciferase construct. The clone B1 exhibited a near linear increase in luminescence from 0.2 mU/l to 50 mU/l bovine TSH and was used as a TBII bioassay. TBII, free T4 and TSH were measured in the sera of all patients and controls.


RESULTS
In the sera of 35 GD patients, TBII titres did not correlate with serum free T4 concentrations. In contrast, a strong and highly significant correlation was found between TSHR stimulating activity (luminescence) as measured with the TBII bioassay and serum free T4 levels (R = 0.80, P < 0.001). Interestingly, the luminescence/TBII ratio had a wide range at low TBII titres, whereas high TBII titres were associated with a low degree of TSHR activation. The TBII bioassay also detected TBAb in GD patients who spontaneously developed hypothyroidism.


CONCLUSIONS
The B1-TBII-bioassay as developed in our laboratory has a high sensitivity for the detection of TSAb in GD and predicts the severity of hyperthyroidism in untreated GD patients. In addition, we found that high TBII titres are associated with weak TSHR activation.
Department of Endocrinology, Leiden University Medical Center, Leiden, Netherlands.
G C J
GC
Hovens
A M J
AM
Buiting
M
M
Karperien
B E P B
BE
Ballieux
G
G
van der Pluijm
A M
AM
Pereira
J A
JA
Romijn
J W A
JW
Smit
D000328:Adult; D019138:Antibodies, Blocking / Q000097:blood; D001323:Autoantibodies / Q000097:blood*; D001681:Biological Assay / Q000379:methods; D016022:Case-Control Studies; D002460:Cell Line; D005260:Female; D006111:Graves Disease / Q000097:blood*; D006801:Humans; D018828:Immunoglobulins, Thyroid-Stimulating / Q000097:blood; D008163:Luminescent Measurements; D008297:Male; D011989:Receptors, Thyrotropin / Q000097:blood / Q000276:immunology*; D013963:Thyroid Hormones / Q000097:blood*
D019138:Antibodies, Blocking; D001323:Autoantibodies; D018828:Immunoglobulins, Thyroid-Stimulating; D011989:Receptors, Thyrotropin; D013963:Thyroid Hormones; C094372:thyrotropin-binding inhibitory immunoglobulin