Association of Polymorphism at Position 49 in Exon 1 of the Cytotoxic T-Lymphocyte-Associated Factor 4 Gene with Graves' Disease Refractory to Medical Treatment,but Not with Amiodarone-Associated Thyroid Dysfunction

Abstract

Background:

Recently, the G allele of the cytotoxic T-lymphocyte-associated factor 4 (CTLA-4) exon 1 single-nucleotide polymorphism (CTLA-4 A/G⁴⁹) has been identified as the most informative marker in patients with Graves' disease. Patients with the G/G genotype are refractory to medical treatment and frequently relapse after discontinuation of antithyroid drugs. Therefore, we analyzed CTLA-4 A/G⁴⁹ in patients who had been treated with ¹³¹I. Further, a preliminary report has suggested that amiodarone-associated thyroid dysfunction (AATD) has a relationship with human leukocyte antigen (HLA) class I and class II.

Method:

CTLA-4 genotypes in exon 1 (A/G⁴⁹) and CT60 were analyzed in 415 Japanese patients with Graves' disease and 65 patients with AATD.

Results:

The frequencies of the G alleles and G/G genotype at the both polymorphisms were significantly higher in Graves' patients compared with normal subjects. Compared with CT60, the frequencies of the G alleles and G/G genotypes at the A/G⁴⁹ were more significantly higher in patients with persistently positive thyrotropin receptor antibody despite >5 years of antithyroid drug therapy, compared with those whose thyrotropin receptor antibody became negative in <5 years (p < 0.0001). Consequently, the frequencies of the G/G genotype and G allele at the A/G⁴⁹ were also significantly higher in patients with Graves' disease who received ¹³¹I therapy (p < 0.05). However, there was no significant difference in the A/G polymorphisms in the 65 patients with AATD.

Conclusions:

The G/G genotype in exon 1 (A/G⁴⁹) is frequently expressed in Graves' disease patients who are refractory to antithyroid drug treatment. Therefore, the G/G genotype in A/G⁴⁹ would be a useful predictor of Graves' patients who are suitable for radioiodine therapy. Although the number of analyzed patients was small, our preliminary data suggest that the CTLA-4 gene polymorphisms might be unassociated with AATD.

Introduction

A utoimmune thyroid diseases, including Graves' disease and Hashimoto's thyroiditis, have recently been reported to have a strong contribution to susceptibility by the HLA locus (1), and are also known to be associated with and/or linked to the cytotoxic T-lymphocyte-associated factor 4 (CTLA-4) locus (1 –3). The CTLA-4 gene is a major negative regulator of T-cell-mediated immune responses (4). CTLA-4 polymorphism, a microsatellite marker located in the 3′-untranslated region, was the first nucleotide polymorphism found to be associated with Graves' disease (5). Subsequently, a single-nucleotide polymorphism in the CTLA-4 leader peptide that encoded a threonine to alanine change in exon 1 (A/G⁴⁹) was also found to be associated with Graves' disease in a number of studies (6 –12). Further, Kinjo et al. (13) reported that the GG genotype in this single-nucleotide polymorphism (A/G⁴⁹) is associated with refractory response to antithyroid agents. Although CT60 is also related to Graves' disease (14), A/G at position 49 in exon 1 is the most informative marker for predicting relapse of Graves' disease in Okinawan Japanese, and in Taiwan Chinese (15).

Recently, amiodarone-associated thyroid dysfunction (AATD) has been increasing steadily worldwide. One form of AATD is amiodarone-associated hypothyroidism (AAH). This is an iodine-induced hypothyroidism frequently seen in patients with subclinical Hashimoto's disease (16). The other type of AATD is amiodarone-induced thyrotoxicosis (AIT). Type I AIT is caused by excessive production of thyroid hormone and develops in patients with toxic multinodular goiter and Graves' disease. Type II AIT is caused by excessive release of stored thyroid hormones from the destroyed thyroid gland (16). Although type II AIT has been reported to result from cytotoxicity of an antiarrhythmic agent to thyrocytes (17,18), a preliminary report has indicated that AATD is associated with HLA-B40-, HLA-Cw3-, and HLA-DR5 (19). Therefore, we studied A/G polymorphisms at position 49 in exon 1 and CT60 of the CTLA-4 gene in 415 Japanese patients with Graves' disease and 65 patients with AATD.

Subjects and Methods

This study was approved by the Ethics Committee of Tokyo Women's Medical University. All participants gave informed written consent. Since we were unable to obtain samples from healthy subjects, we compared our data (exon 1 [A/G⁴⁹]) with the Japanese healthy subjects (n = 795) quoted in a meta-analysis of autoimmune thyroid disease performed in Japan (20)—namely, 110 healthy controls on Okinawa island (13), 425 healthy controls in Saitama Prefecture (9), 200 healthy controls in Tokyo (7), and 60 healthy controls in Yamanashi Prefecture (21). Further, we compared our data (CT60) with Japanese healthy subjects (n = 1335)—namely, 179 healthy controls in Tokyo (22), 715 healthy controls in Osaka (23), and 441 healthy controls reported from the Institute of Rheumatology, Tokyo Women's Medical University (24).

Patients with Graves' disease

We studied 415 patients with Graves' disease (315 women and 100 men). Hyperthyroidism caused by Graves' disease was diagnosed on the basis of history and signs of hyperthyroidism with diffuse goiter, and elevated serum levels of thyroxine (T4) and triiodothyronine (T3), accompanied by a suppressed serum thyrotropin (thyroid-stimulating hormone, TSH) level and positivity for TSH receptor antibody (TRAb). Graves' disease patients were divided into three groups according to TRAb disappearance time after the start of antithyroid drug treatment (13). Since only a few patients became TRAb-negative within 1 year, we grouped 96 Graves' patients in whom TRAb had disappeared within 2 years after the start of antithyroid drug treatment (Group A). Group B consisted of 163 patients, in whom TRAb had disappeared between the beginning of the second year and the end of the fifth year after the start of treatment. Group C consisted of 156 patients, in whom TRAb continued to be positive even after 5 years of antithyroid drug treatment. There were no statistically significant differences in initial values of age, sex, and their thyroid function (total T4, T3, TSH, and TRAb) between groups A, B, and C (Table 1).

Table 1.

Clinical Findings in 415 Graves' Disease Patients at Diagnosis

	Total (n = 415)	Group A (n = 96)	Group B (n = 163)	Group C (n = 156)	p-Value
Age	41.0 ± 14.8	40.4 ± 15.2	41.0 ± 14.8	41.3 ± 14.8	n.s.
Sex (M/F)	100/315	28/68	35/128	36/120	n.s.
TRAb (<10%)	62.8 ± 25.7	59.7 ± 24.8	61.1 ± 25.5	64.0 ± 23.6	n.s.
TSH (0.38–4.3 μU/mL)	0.013 ± 0.06	0.007 ± 0.006	0.020 ± 0.08	0.010 ± 0.03	n.s.
T3 (0.9–1.7 ng/mL)	4.0 ± 1.7	3.8 ± 1.7	4.1 ± 1.7	4.2 ± 1.6	n.s.
T4 (5.1–11.4 μg/dL)	17.5 ± 5.0	17.1 ± 5.0	17.3 ± 4.8	18.1 ± 5.2	n.s

In the first column, values within parentheses are reference ranges. Age indicates the age at diagnosis. Data are means ± standard deviation.

M, male; F, female; n.s., not significant; TRAb, TSH receptor antibody; TSH, thyrotropin; T3, triiodothyronine; T4, thyroxine.

The patients were treated with methimazole at an initial dose of 15–30 mg/day, which was reduced gradually as serum thyroid hormone concentrations declined. Thereafter, they received the minimum doses of antithyroid agents to maintain the normal serum levels of T4, T3, and TSH. Patients were seen every 2–4 weeks until their serum T4 and T3 concentrations had normalized. They were then followed every 1–3 months until their TRAb or thyroid-stimulating antibody (TSAb) titer became negative.

Patients with AATD

More than 500 patients with life-threatening arrhythmia have received amiodarone at our Institute of Cardiology over the last 15 years (25). About 10% developed AAH with an elevated serum level of TSH (>20 μU/mL), associated with decreased serum levels of T3 and/or T4, and we were able to analyze 25 patients with AAH. Nearly 50 patients developed AIT with elevated serum levels of T3 and T4, accompanied by a suppressed serum level of TSH (<0.01 μU/mL). As reported previously (25), most AIT patients in Japan, where the dietary iodine level is sufficient, developed type II AIT. Only two of these patients were positive for both TRAb and TSAb, and were found to have Graves' disease (type I AIT) (26). Ten patients who first developed type II AIT and then developed hypothyroidism were included in the type II AIT group. Altogether, we were able to analyze CTLA4 polymorphism in 67 patients with AATD, that is, 25 patients with AAH, 2 patients with type I AIT (Graves' disease), and 40 patients with type II AIT.

Laboratory analysis

Serum values of T4 and T3 were measured using commercial kits (T4, Ecuresis T4 II; T3, Ecuresis T3; Roche Diagnostic, Tokyo, Japan) as reported previously (27). Normal ranges of T4 and T3 were 5.1–11.4 μg/dL and 0.9–1.70 ng/mL, respectively. Serum values of TSH were measured with a third-generation ECLIA kit (Ecuresis TSH; Roche Diagnostic). The normal range of TSH was 0.38–4.30 μU/mL. Serum values of TBII were measured by radioreceptor assay using a commercial kit (Dynotest TRAb human; Yamasa, Okayama, Japan). The results were expressed as percentage inhibition of binding of labeled TSH. The normal value was <10%. TSAb activities were measured in terms of the amount of cAMP produced in cultured porcine thyrocytes (28). The normal range was <180%.

Analysis of CTLA-4 gene polymorphisms

Genomic DNA was prepared from peripheral white blood cells using a DNA purification kit (Qiagen, Hilden, Germany). CTLA-4 genotypes in exon 1 (A/G⁴⁹) were analyzed by polymerase chain reaction (13), using genomic DNA (0.2 μg), Taq polymerase (1 U) (Takara, Shiga, Japan), 10 pmol of each primer (forward, 5′-GCT CTA CTT CCT GAA GAC CT-3′; reverse, 5′-AGT CTC ACT CAC CTT TGC AG-3′), and dNTPs (200 μM) under the following conditions: initial denaturation for 4 minutes at 94°C, annealing for 45 seconds at 54°C, extension for 45 seconds at 72°C, denaturation for 45 seconds at 94°C (35 cycles), and a final extension for 4 minutes at 72°C. The presence of G alleles was determined by digestion with Bbv1 (New England Biolabs, Ipswich, MA), which acts on the G variant, but not on the A variant. If a G allele was found at position 49, then 88/74-base pair fragments were obtained. Polymerase chain reaction products were detected by electrophoresis in a 3% agarose gel.

CTLA-4 polymorphism at CT60 was analyzed, using the 10 pmol of each primer (forward, 5′-ATA ATG CTT CAT GAG TCA GCT T-3′; reverse, 5′-GAG GTG AAG AAC CTG TGT TAA A-3′) (29). The presence of G allele was determined by Tai I (Mae II) (Formentus, Burlington, Canada) at 65°C for 6 hours, which acts on the G variant, but not A variant. If a G allele was found at CT60, then 109/69-base pair fragments were obtained.

Statistical analyses

The differences between groups A, B, and C (age, TRAb, TSH, T3, and T4) were statistically analyzed using one-factor analysis of variance, respectively. Statistical analyses of the differences between groups were also made using χ ²-test with Yate's correction, Fisher's exact probability test, or two-tailed unpaired t-test. Either 3 × 2 or 3 × 3 contingency tables were used to analyze the allele or genotype, respectively. Differences at p < 0.05 were considered statistically significant.

Results

Genotype frequencies at position 49 in exon 1 of the CTLA-4 gene in Graves' patients

As shown in Table 2a, the frequencies of the G alleles in exon 1 (A/G⁴⁹) were significantly higher in patients with Graves' disease than in normal Japanese subjects. This was also the case with CT60 (Table 2b).

Table 2.

Frequencies of Genotypes and Alleles of A/G Polymorphisms of the Cytotoxic T-Lymphocyte-Associated Factor 4 Gene in Graves' Disease Patients and Controls

(a) A/G Polymorphism in Exon 1 (A/G⁴⁹)
	Graves' disease (n = 415)	Japanese controls (n = 795)	χ²	p-Value
Genotype
G/G	210 (50.6%)	295 (37.1%)	20.64	<0.0001
A/G	143 (34.5%)	358 (45.0%)
A/A	62 (14.9%)	142 (17.9%)
Allele
G	563 (67.8%)	948 (59.6%)	15.67	<0.0001
A	267 (32.2%)	642 (40.4%)	15.67	<0.0001

Data are reported as a number (%).

(b) A/G Polymorphism in CT60
	Graves' disease (n = 415)	Japanese controls (n = 1335)	χ²	p-Value
Genotype
G/G	267 (64.3%)	735 (55.1%)	11.15	<0.005
A/G	127 (30.6%)	516 (38.7%)
A/A	21 (5.1%)	84 (6.3%)
Allele
G	661 (79.6%)	1986 (74.4%)	9.49	<0.005
A	169 (20.4%)	648 (25.6%)	9.49	<0.005

Data are reported as a number (%).

When the patients were divided into three groups (A, B, and C) according to TRAb disappearance time after the start of antithyroid drug treatment, the frequencies of the G/G genotype and G allele in exon 1 (A/G⁴⁹) were significantly higher in the patients with persistently positive TRAb (>5 years, Group C) than those in whom TRAb disappeared within 5 years (Group B) (p < 0.005) or within 2 years (Group A) (p < 0.0001) (Table 3a). In accordance with the report of Wang et al. (15), the frequencies of the G/G genotype and G allele in CT 60 were also increased in Graves' patients refractory to medical treatment; however, statistical significance was weaker (p < 0.05) compared with that obtained from exon 1 (A/G⁴⁹) polymorphism (Table 3b).

Table 3.

Cytotoxic T-Lymphocyte-Associated Factor 4 Polymorphisms and Thyrotropin Receptor Antibody Disappearance

(a) A/G Polymorphism in Exon 1 (A/G⁴⁹)
	Genotypes (n = 415)			p-Value a	Alleles (n = 830)		p-Value b
Group	G/G	A/G	A/A	<0.00001	G	A	<0.0001
Group A	36	31	29		103	89
Group B	75	64	24		214	112
Group C	99	48	9		246	66

Data are reported as a number.

(b) A/G Polymorphism in CT60
	Genotypes (n = 415)			p-Value a	Alleles (n = 830)		p-Value b
Group	G/G	A/G	A/A	<0.05	G	A	<0.005
Group A	51	35	10		137	55
Group B	111	48	4		270	56
Group C	105	44	7		254	169

Data are reported as a number.

Group A: TRAb had disappeared within 2 years after the start of antithyroid drug treatment.

Group B: TRAb had disappeared between the beginning of the 2 years and the end of the 5 years after the start of antithyroid drug treatment.

Group C: TRAb continued to be positive after 5 years of antithyroid drug treatment.

^aStatistical analysis with 3 × 3 contingency tables.

^bStatistical analysis with 3 × 2 contingency tables.

A/G polymorphism in the CTLA-4 gene in Graves' patients treated with ¹³¹I

Although initially almost all Graves' patients received antithyroid drug therapy, 58 patients who were refractory to medical treatment or had adverse reactions within a few months were treated with ¹³¹I. Since 9 patients who had an adverse reaction such as skin rash or agranulocytosis were excluded, 49 patients treated with radioiodine because of protracted hyperthyroidism despite >5 years of medical treatment were analyzed statistically. The frequencies of the G/G genotype and G allele in exon 1 (A/G⁴⁹) were significantly higher in these patients with ¹³¹I therapy than in those without ¹³¹I therapy (p < 0.05) (Table 4a). However, there was no significant difference in the frequencies of the G/G genotype and G allele in CT60 in Graves' patients with or without ¹³¹I therapy (Table 4b).

Table 4.

Frequencies of Genotypes and Alleles of Cytotoxic T-Lymphocyte-Associated Factor 4 and Graves' Disease Patients Treated with ¹³¹I

(a) A/G Polymorphism in Exon 1 (A/G49)
Radioiodine therapy	Genotypes (n = 406)			p-Value a	Alleles (n = 812)		p-Value b
	G/G	A/G	A/A	<0.05	G	A	<0.05
RI (+)	28	20	1		76	22
RI (−)	176	120	61		472	242
Total	204	140	62		548	264

Data are reported as a number.

Of the 59 patients treated with ¹³¹I, 9 patients who developed adverse reaction to antithyroid drugs (6 cases had G/G, 3 cases A/G genotypes) were excluded from statistical analysis.

(b) A/G Polymorphism in CT60
Radioiodine therapy	Genotypes (n = 406)			p-Value a	Alleles (n = 812)		p-Value b
	G/G	A/G	A/A	0.92 (n.s.)	G	A	0.96 (n.s.)
RI (+)	31	16	2		78	20
RI (−)	231	108	18		570	144
Total	262	124	20		648	164

Data are reported as a number.

Of the 59 patients treated with ¹³¹I, 9 patients who developed adverse reaction to antithyroid drugs (5 cases had G/G, 3 cases A/G, and 1 case A/A genotypes) were excluded from statistical analysis.

^aStatistical analysis with 3 × 3 contingency tables.

^bStatistical analysis with 2 × 2 contingency tables.

RI (+), radioiodine therapy; RI (−), without radioiodine therapy.

A/G polymorphisms of the CTLA-4 gene in patients with AATD

Two patients who developed type I AIT were excluded from the statistical analysis. We analyzed 65 patients with AATD—namely, 25 patients with AAH and 40 patients with type II AIT. Although the number of patients was small, there was no significant difference in CTLA-4 gene polymorphism in exon 1 (A/G49) between AATD (n = 65) and control subjects (n = 795) (p = 0.12). There was also no significant difference between type II AIT (n = 40) and control subjects (n = 795) (p = 0.39) (Table 5a). The same results were obtained with CT60 (Table 5b).

Table 5.

Frequencies of Genotypes and Alleles of Cytotoxic T-Lymphocyte-Associated Factor 4 in Patients in Amiodarone-Associated Thyroid Dysfunction, Type II Amiodarone-Induced Thyrotoxicosis, and Japanese controls

(a) A/G Polymorphism in Exon 1(A/G49)
	AATD (n = 65)	p-Value	Type II AIT (n = 40)	p-Value	Controls (n = 795)
Genotype
G/G	31 (47.7%)	p = 0.17 (n.s.)	21 (52.5%)	p = 0.14 (n.s.)	295 (37.1%)
A/G	22 (33.8%)		14 (35.0%)		358 (45.0%)
A/A	12 (18.5%)		5 (12.5%)		142 (17.9%)
Allele
G	88 (64.6%)	p = 0.26 (n.s.)	56 (70.0%)	p = 0.06 (n.s.)	948 (59.6%)
A	42 (35.4%)	p = 0.26 (n.s.)	24 (30.0%)	p = 0.06 (n.s.)	642 (40.4%)

Data are reported as a number (%).

Of the 67 AATD patients, 2 patients who developed type I AIT due to Graves' disease (A/G, A/G) were excluded from statistical analyses.

AATD, amiodarone-associated thyroid dysfunction; AIT, amiodarone-induced thyrotoxicosis.

(b) A/G Polymorphism in CT60
	AATD (n = 65)	p-Value	Type II AIT (n = 40)	p-Value	Controls (n = 1335)
Genotype
G/G	41 (63.1%)	p = 0.42 (n.s.)	28 (70.0%)	p = 0.17 (n.s.)	735 (55.1%)
A/G	20 (30.8%)		10 (25.0%)		516 (38.7%)
A/A	4 (6.2%)		2 (5.0%)		84 (6.3%)
Allele
G	102 (78.5%)	p = 0.30 (n.s.)	66 (82.5%)	p = 0.10 (n.s.)	1986 (74.4%)
A	28 (21.5%)	p = 0.30 (n.s.)	14 (17.5%)	p = 0.10 (n.s.)	684 (25.6%)

Data are reported as a number (%).

Of the 67 AATD patients, 2 patients who developed type I AIT due to Graves' disease (G/G, A/G) were excluded from statistical analyses.

Discussion

We confirmed the report of Kinjo et al. (13), who indicated that the frequencies of the G/G genotype and G allele in exon 1(A/G⁴⁹) were significantly higher in patients with persistently positive TRAb (>5 years) than those in whom TRAb became negative in <5 years. Graves' patients who continued to have TRAb positivity after 5 years of antithyroid drug therapy had a low frequency of the A/A genotype, suggesting that the GG phenotype is a factor associated with poor response to medical treatment. Although the statistical power was marginal because of the small number of patients (n = 114), our data confirmed the previous observation that Graves' patients with a G/G genotype are refractory to medical treatment, based on a much larger number of patients (n = 415). Indeed, the power calculation using the method of Cohen (30), assuming an α-power level set at 0.05 (two-sided), revealed that the power to check the association was weak in the study by Kinjo et al. based on 114 patients. In contrast, our data based on 415 patients were significantly strong, since >280 patients were analyzed to obtain power values above 0.8. We also confirmed that the frequencies of the G/G genotype and G allele in CT60 were significantly higher in patients with Graves' disease (14,15), but the refractoriness to medical treatment is more significantly associated with G allele in exon 1(A/G⁴⁹) than that in CT60 (15).

Consistent with these findings, the frequencies of the G/G genotype and G allele in exon 1(A/G⁴⁹) were significantly higher in the patients who received ¹³¹I therapy than in Graves' patients treated with antithyroid drugs. Although a considerable number of Japan Thyroid Association members believe that more radioiodine therapy should be applied to achieve a rapid improvement of hyperthyroidism, for convenience, and for medical cost benefits (31), most Japanese patients with Graves' disease are reluctant to receive ¹³¹I therapy due to phobia against radiation, and prefer to take antithyroid agents for many years. Although this was a retrospective study, we would like to recommend ¹³¹I therapy for Graves' patients who have continued to take antithyroid agents for more than 2–3 years, particularly when their genotype in exon 1(A/G⁴⁹) is GG.

As a recent meta-analysis clearly demonstrated, the polymorphisms in exon 1(A/G⁴⁹) and CT60 of CTLA-4 are an important genetic determinant for the risk of Graves' disease across diverse populations (19). However, there is a report that these polymorphisms are not associated with Graves' disease in Koreans (32). In normal Korean people, however, GG genotypes of A/G⁴⁹ in exon 1 and CT60 is 51.8% and 70.8%, respectively, whereas they are 37.1% and 55.1%, respectively, in Japanese people (Table 2a and b). Such an ethnic difference in the allele frequency may have influenced on the power of detecting association of CTLA-4 polymorphism with Graves' disease in Koreans.

CTLA-4 is an immunoregulatory molecule expressed on the surface of activated T lymphocytes and a key inhibitor of T-cell activation. Several lines of evidence support its role as a key negative regulator of T-cell activation. Further, in most autoimmune diseases, susceptibility has also been linked closely with major histocompatibility complex (MHC) class II alleles. Presumably, this is because T-cells recognize the antigen presented by MHC class II on antigen-presenting cells, and this interaction makes the MHC class II region a strong candidate for involvement in T-cell-mediated autoimmune disease (1 –3). Kouki et al. (33) reported that lymphocytes of Graves' patients with the G/G genotype in exon 1 (A/G⁴⁹) showed greater proliferation than those from patients with the A/A phenotype. When anti-human CTLA-4 antibody was used to unmask its negative regulatory action, T-cell proliferation was found to be related to the G/G genotype in individuals with Graves' disease and Hashimoto' thyroiditis, and in normal controls.

Although AATD may be related to HLA-B40-, HLA-Cw3-, and HLA-DR5 (19), our preliminary data suggest that CTLA-4 gene polymorphisms at exon 1(A/G⁴⁹) and CT60 would be unassociated with them. It is likely that certain cytotoxic effects of amiodarone on thyrocytes may be somehow involved in AATD, particularly in type II AIT (17,18).

In conclusion, our study based on 415 patients has confirmed that A/G polymorphism at position 49 in exon 1 of the CTLA-4 gene is associated with a poor response to medical treatment in Graves' disease patients, and consequently is significantly increased in patients treated with ¹³¹I. Therefore, when Graves' patients have been taking antithyroid agents for more than a few years and if their CTLA-4 A/G⁴⁹ is the G/G genotype, it would be reasonable to recommend ¹³¹I therapy at an earlier stage. Although the number of patients with AATD analyzed was small, our preliminary data suggest that the CTLA-4 gene might be unassociated with AATD.

Footnotes

Acknowledgment

This work was partly supported by Grants-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan (20591102).

Disclosure Statement

The authors declare that no competing financial interests exist.

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Association of Polymorphism at Position 49 in Exon 1 of the Cytotoxic T-Lymphocyte-Associated Factor 4 Gene with Graves' Disease Refractory to Medical Treatment,but Not with Amiodarone-Associated Thyroid Dysfunction

Abstract

Background:

Method:

Results:

Conclusions:

Introduction

Subjects and Methods

Patients with Graves' disease

Patients with AATD

Laboratory analysis

Analysis of CTLA-4 gene polymorphisms

Statistical analyses

Results

Genotype frequencies at position 49 in exon 1 of the CTLA-4 gene in Graves' patients

A/G polymorphism in the CTLA-4 gene in Graves' patients treated with 131I

A/G polymorphisms of the CTLA-4 gene in patients with AATD

Discussion

Footnotes

Acknowledgment

Disclosure Statement

References

A/G polymorphism in the CTLA-4 gene in Graves' patients treated with ¹³¹I