Diagnostic Utility of a New Assay for Thyroid Stimulating Immunoglobulins in Graves' Disease and Thyroid Eye Disease.

Background: The syndrome of thyrotoxicosis typically relies on radioactive iodine scans for establishing its etiology. Alternatively, the determination of thyrotropin (TSH) receptor antibodies (TRAbs) helps to distinguish Graves' disease (GD) from thyrotoxic thyroiditis. Current assays are impacted by limitations in sensitivity and/or turnaround time. Therefore, we decided to test a new assay for the detection of TSH receptor stimulating antibodies (TSAbs) and compare it with the clinically available assays. Methods: We enrolled 110 individuals in 5 cohorts: patients with incident or recurrent GD (cohort 1); patients with thyroiditis, painless or subacute (cohort 2); patients with Graves' orbitopathy/thyroid eye disease (TED) in cohort 3; patients with Hashimoto's thyroiditis (cohort 4), and a control group of normal volunteers (cohort 5). The patients were tested with the two clinically available assays: Roche Elecsys anti-TSHR assay (ROC-TBII) from Roche Diagnostics and Thyretain™ TSI Reporter BioAssay Kit (QUI-TSI) from Quidel. In addition, the samples were tested with the aequorin TSAb assay (OTS-TSI) provided by Otsuka Pharmaceutical Co., Ltd. (Tokyo, Japan). The data were collected in a cross-sectional manner before initiation of therapy. Results: We had 36 cases of GD, 17 cases of thyroiditis, 27 cases of TED, 10 cases of Hashimoto's thyroiditis, and 20 normal volunteers. OTS-TSI had 100% sensitivity and specificity in distinguishing GD from thyroiditis, identical with QUI-TSI but superior to ROC-TBII (sensitivity 86% and specificity 94.1%). OTS-TSI had 93% sensitivity and 100% specificity for the diagnosis of TED, compared with normal controls. QUI-TSI and ROC-TBII performed similarly in this analysis, demonstrating 82% sensitivity and 100% specificity. The range of detectable values for OTS-TSI was 20-29,000 mIU/L and the turnaround time was ≤6 hours, without the need for cell culture equipment. Conclusions: OTS-TSI performed excellently, though similarly to QUI-TSI, for the differential diagnosis of GD vs. thyroiditis, while being superior in that respect to ROC-TBII. Furthermore, OTS-TSI has superior sensitivity to QUI-TSI and ROC-TBII for TED diagnosis, while retaining high specificity. It has a short turnaround time and avoids the need for cell culture and sterility. Larger studies in U.S. populations are needed for its validation.

Role of a new bioassay for thyroid-stimulating antibodies (aequorin TSAb) in Graves' ophthalmopathy.

Graves' ophthalmopathy (GO) is characterized by an autoimmune reaction against thyrotropin (TSH) receptors and is diagnosed by TSH receptor antibody (TRAb). A novel assay for thyroid-stimulating antibody (TSAb) was recently introduced using a frozen Chinese hamster ovary cell line expressing TSH receptors, cyclic adenosine monophosphate (cAMP)-gated calcium channel, and aequorin (aequorin TSAb). The aim of this study was to evaluate the role of aequorin TSAb in GO. We studied 136 Japanese patients with GO (22 euthyroid and 8 hypothyroid GO patients) at our hospital. TRAbs were estimated by first generation TRAb (TRAb 1st), second generation TRAb (hTRAb 2nd), conventional porcine TSAb, and the new aequorin TSAb assays. Aequorin TSAb, porcine TSAb, TRAb 1st, and hTRAb 2nd were positive in 125/136 (92%), 110/136 (81%), 81/130 (62%), and 93/114 (82%) patients, respectively. In patients with hyperthyroid GO, they were positive in 98/106 (98%), 96/106 (91%), 78/101 (77%), and 84/93 (90%) patients, respectively. In patients with euthyroid GO, they were positive in 19/22 (86%), 9/22 (41%), 1/21 (5%), and 6/17 (35%) patients, respectively. Aequorin TSAb levels were significantly related to TRAb 1st (r = 0.4172, p < 0.0001), hTRAb 2nd (r = 0.2592, p < 0.0001), and porcine TSAb (r = 0.4665, p < 0.0001). Clinical activity score (CAS) was significantly greater in patients with high titers of aequorin TSAb than in those with low titers. Aequorin TSAb levels were significantly related to the signal intensity ratio of the enlarged eye muscle and proptosis evaluated by MRI before steroid pulse therapy. Aequorin TSAb assay was more sensitive than the conventional assays, especially in euthyroid GO.

Rapid bioassay for detection of thyroid-stimulating antibodies using cyclic adenosine monophosphate-gated calcium channel and aequorin.

BACKGROUND: Thyroid-stimulating antibodies (TSAb) are known to be responsible for hyperthyroidism in Graves' disease (GD). The conventional methods to measure TSAb depend on cell-based assays that require cumbersome procedures and a sterilized tissue culture technique. The aim of the present study was to develop a ready-to-use cell-based assay for measuring TSAb activity without requiring sterilized conditions. METHODS: We developed a new assay kit using a frozen Chinese hamster ovary cell line expressing the thyroid-stimulating hormone receptor, cyclic adenosine monophosphate (cAMP)-gated calcium channel and aequorin, tentatively named the aequorin TSAb assay. Activated stimulatory G-protein-coupled adenylate cyclase increases intracellular cAMP, which then binds to the cyclic nucleotide-gated calcium channel. Activation of this channel allows Ca(2+) to enter the cell, and the influx of Ca(2+) can be measured with aequorin, which is quantified by a luminometer. Results can be obtained in only 4 h without sterilized conditions. TSAb activities were expressed by international units using the NIBSC 08/204 standard. RESULTS: Positive results of aequorin TSAb were obtained in 197 of 199 (98.9%) of untreated patients with GD. Only 1 of 42 (2.3%) patients with painless thyroiditis had a weakly positive aequorin TSAb. All 45 patients with subacute thyroiditis and 185 normal subjects showed negative aequorin TSAb. As for chronic thyroiditis, all 52 euthyroid patients showed negative aequorin TSAb, but 8 of 50 (16.0%) hypothyroid patients had a positive reaction. However, these positive reactions were not induced by serum thyroid-stimulating hormone (TSH) and were thought to be induced by the stimulating activity of anti-TSH receptor immunoglobulins. Conventional porcine TSAb and Elecsys thyroid-stimulating hormone receptor antibodies were positive in 69.3 and 95.5% of GD, respectively. CONCLUSION: The aequorin TSAb assay was positive in 98.9% of GD and was more sensitive than the conventional assay. This assay can be conducted in only 4 h without sterilized conditions and is practically useful in general clinical laboratories.

Screening for androgen receptor activities in 253 industrial chemicals by in vitro reporter gene assays using AR-EcoScreen cells.

Recently, there has been great concern about the potential of industrial chemicals to act as endocrine disrupters. In this report, we conducted a pilot study to validate the use of AR-EcoScreen cells for tier 1 screening of androgen receptor (AR) agonist and antagonist activities. From 253 test compounds, we identified two AR agonists and nine antagonists. The two agonists, 2-tert-butylanthraquinone and benzoanthrone, were relatively weak (10% maximal activation of the positive control, 5alpha-dihydrotestosterone, at 2.54x10(-7) and 4.46x10(-6) M, respectively). The most potent antagonist was 3,3'-dichlorobenzidine dihydrochloride (IC50 = 2.28x10(-7) M). The order of the anti-androgenic activities was 3,3'-dichlorobenzidine dihydrochloride>4-diethylaminobenzaldehyde>4,4'-[1-[4-[1-(4-hydroxyphenyl)-1-methylethyl]phenyl]ethylidene]bis[phenol]>2,4,6-trichlorophenylhydrazine = 4-(phenylpropyl)pyridine>2-hydroxy-4-methoxybenzophenone>2,2-bis(4-cyanophenyl)propane>4-methoxy-2-methyldiphenylamine = 2,4-diphenyl-4-methylpentene-1. These results suggest that AR-EcoScreen cell line has the potential to be used as a tool for the large scale tier 1 screening of chemicals for androgen receptor agonist and antagonist activity.

Evaluation of a rapid in vitro androgen receptor transcriptional activation assay using AR-EcoScreen cells.

An accurate and reliable in vitro assay system has been needed for first tier screening of endocrine disrupting chemicals. For the purpose, we previously developed stable AR-EcoScreen cell lines to assess androgen receptor (AR)-mediated transcriptional activation. In this report, we evaluated AR-EcoScreen cell lines as the phase I of prevalidation study by determining the intra-laboratory reproducibility, assay stability, and overall protocol performance of AR-EcoScreen assays. Forty compounds recommended by the ICCVAM were tested for AR agonist and antagonist activity. The mean coefficient of variation (CV) for intra-assay reproducibility in the AR agonist assay was 4.35% for 5alpha-dihydrotestosterone (DHT), and that for the antagonist assay was 5.51% for hydroxyflutamide. The detection limit of the agonist assay was 2.3x10(-11) M for 5alpha-dihydrotestosterone. Furthermore, we examined the overall performance of the method by comparing the predicted result with the ICCVAM classification. Thus, the overall sensitivity, specificity, and accuracy of the agonist assay were 89%, 94%, and 91%, respectively. For the antagonist assay, these values were 94%, 100%, and 96%, respectively. In summary, we concluded that AR-EcoScreen method was ready to proceed to the phase II prevalidation study to asses the inter-laboratory variability and transfer of the protocol.

A novel nonradioactive method for measuring aromatase activity using a human ovarian granulosa-like tumor cell line and an estrone ELISA.

Aromatase is a key enzyme in steroidogenesis and plays an important role in sexual differentiation, fertility, and carcinogenesis. Importantly, a variety of chemicals in the environment may influence its activity and thereby disrupt endocrine function. In the current studies, we developed a novel nonradioactive method for measuring aromatase activity that uses a specific ELISA for estrone along with KGN human ovary granulosa-like carcinoma cells. This cell line has relatively high aromatase activity, and because it lacks 17alpha-hydroxylase, it secretes little or no androstenedione, 17beta-estradiol, or estrone. Therefore, aromatase activity can be assayed simply by measuring the production of estrone in the culture medium after addition of the substrate, androstenedione. Furthermore, by making a slight change in the commercial ELISA kit and optimizing the experimental conditions, we developed a sensitive aromatase assay that could measure a wide range of estrone concentrations with very low interference by androgens. We used this assay to investigate the effects of 23 chemicals that have been previously reported to affect aromatase activity in vitro. We confirmed that 17 of 23 test chemicals had inhibitory or inducible effects, although the specific effects of some were different than previously reported. In conclusion, we have developed a simple, sensitive, and nonradioactive assay that can be used for large-scale screening of compounds that can disrupt endocrine function by influencing aromatase activity.