Hypothyroid Hashimoto's Thyroiditis Research Articles

Hashimoto's Thyroiditis, but not Treatment of Hypothyroidism, Is Associated with Altered TGF-β1 Levels

Although the role of cytokines in the development of Hashimoto's thyroiditis has already been established, its pathogenesis has not yet been clearly elucidated. The aim of our study was to investigate serum transforming growth factor-beta1 (TGF-beta1) levels in patients with Hashimoto's thyroiditis as well as the effect of achieving euthyroidism by levothyroxine replacement on TGF-beta1 levels. Twenty nine female, newly diagnosed hypothyroid Hashimoto's thyroiditis patients (16 overt, 13 subclinical hypothyroid) and 25 age- and sex-matched healthy controls were enrolled in the study. Serum TGF-beta1 levels were lower in the Hashimoto's thyroiditis group when compared with control cases. Although significant differences were noted in lipid levels and in anthropometric measurements following levothyroxine replacement, serum TGF-beta1 levels remained unchanged. Our data suggest that altered TGF-beta1 levels are associated with the presence of Hashimoto's thyroiditis, not with the treatment of thyroid dysfunction. Autoimmunity may have been triggered as a result of decreased immunosuppressive effect induced by depressed TGF-beta1 levels in patients with Hashimoto's thyroiditis.

Hashimoto's thyroiditis and insulin-dependent diabetes mellitus: differences among individuals with and without abnormal thyroid function.

Insulin-dependent diabetes mellitus probands from the Familial Autoimmune and Diabetes Study were evaluated for autoimmune thyroid disease (n = 265). The prevalence of Hashimoto's thyroiditis was 26.6%; 42.0% of these individuals were euthyroid, and 58.0% were hypothyroid. There was a female predominance among hypothyroid and euthyroid Hashimoto's cases compared to those with no thyroid disease (75% vs. 72.4% vs. 41.6%; P < 0.001). Insulin-dependent diabetes mellitus patients with hypothyroid Hashimoto's thyroiditis were more likely to report another autoimmune disease compared to euthyroid Hashimoto's patients or individuals with no thyroid disease (30.8% vs. 17.2% vs. 13.9%; P < 0.01). Sex-specific analysis revealed that this difference was significant for men but not for women. Both euthyroid and hypothyroid Hashimoto's cases were more likely to have a family history of the disease (66.7% vs. 69.2% vs. 47.7%; P < 0.05). No differences were observed in the prevalence of DQA1*0501-DQB1*0201 or DQA1*0301-DQB1*0302 across the three groups. Body mass index, lipid levels, glycemic control, and diabetes complications were also similar. However, euthyroid Hashimoto's women were more likely to report spontaneous abortions than those with hypothyroid Hashimoto's thyroiditis or no thyroid disease (23.8% vs. 61.5% vs. 29.1%; P < 0.05). These data suggest that gender-specific risk factors may be primary determinants of Hashimoto's thyroiditis and other autoimmune diseases among women. However, disease-specific determinants may also increase susceptibility to other autoimmune diseases.

Heterogeneity of Autoantibodies against Thyroid Peroxidase in Autoimmune Thyroid Disease: Evidence against Antibodies Directly Inhibiting Peroxidase Activity as Regulatory Factors in Thyroid Hormone Metabolism

The close relationship between thyroid microsomal antigen and thyroid peroxidase (TPO) is now well established. The present study evaluates the significance of autoantibodies against TPO (anti-TPO-Abs) in the various forms and stages of autoimmune thyroid disease with respect to a possible heterogeneous nature and particularly to their influence on TPO activity. When measured by a RIA using purified human TPO, anti-TPO-Abs were highly correlated with microsomal antibodies determined by enyzme-linked immunosorbant assay (r = 0.96; P less than 0.0001) and with the results of a TPO immunoprecipitation assay using crude microsomal preparations (r = 0.76; P less than 0.001). Relating the results of these assays to the reactivities of patients' sera with thyroid microsomes in immunoblot under nonreducing and reducing conditions, discordant results could be observed in a few cases. Further analysis of these data indicate a heterogeneous nature of anti-TPO-Abs, which react with at least two antigenic domains of the TPO molecule. The comparative analysis of patients with hyperthyroid Graves' disease, patients with Graves' disease in clinical remission, and patients with hypothyroid Hashimoto's thyroiditis revealed no significant differences in the antibody spectrum. When evaluating the direct influence of anti-TPO-Abs on the activity of TPO under a rigorous methodological approach, we found no significant inhibition of the enzymatic activity by any of the sera investigated from patients with autoimmune thyroid disease compared to that in sera from normal controls. In conclusion, the data indicate a heterogeneous nature of anti-TPO-Abs. The spectrum of antigenic epitopes recognized by anti-TPO-Abs seems not to be significantly different in the various forms and stages of autoimmune thyroid disease. The lack of an inhibitory effect of autoantibodies on TPO activity argues against direct binding of autoantibodies to the enzymatic sites of TPO and indicates that they are not important factors in producing thyroid dysfunction in autoimmune thyroid disease.

Studies of CD4+ (Helper/Inducer) T Lymphocytes in Autoimmune Thyroid Disease: Demonstration of Specific Induction in Response to Thyroid Peroxidase (TPO) In Vitro and Its Relationship with Thyroid Status In Vivo

We have studied by flow cytometric analysis the antigen specific activation of CD4+ (helper/inducer) T lymphocytes by purified human thyroid peroxidase (TPO). Peripheral blood mononuclear cells were obtained from 26 patients with Graves' disease (GD), 16 with Hashimoto's thyroiditis (HT), 7 with nontoxic nodular goiter (NG), and 14 normal subjects (N). Cells were cultured for 7 days in the presence or absence of TPO at final concentrations of 3, 30, and 300 ng/mL. When harvested, cells were reacted with an FITC-conjugated anti-CD4 and a PE-conjugated anti-HLA-DR murine monoclonal antibodies. The percentage of HLA-DR+ CD4+ cells (activated CD4+ cells) was determined by a flow cytometer. In the absence of TPO, CD4+ cells had been activated without any specific stimulant. This is known as the autologous mixed lymphocyte reaction (AMLR). In the AMLR, CD4+ cells from GD and HT were less activated compared to those from NG and N. Results of TPO-specific activation were expressed as an incremental increase of activated CD4+ cells (II) (percentage of activated CD4+ cells cultured with TPO minus percentage of activated CD4+ cells cultured without TPO). II of N, GD, HT, and NG were 0.37 +/- 0.21, 2.20 +/- 0.45,** 2.0 +/- 0.66,* and 0.35 +/- 0.27 (mean +/- SEM), respectively (**p less than 0.01; *p less than 0.05 vs N). When patients were further subdivided, the highest mean II was found in patients with hyperthyroid GD (p less than 0.01), followed by euthyroid HT (p less than 0.05) and euthyroid GD (p less than 0.05), however there was no significant difference between hypothyroid HT and N. In conclusion (1) AMLR reactivity of CD4+ cells from GD and HT was impaired, (2) however, CD4+ cells from both GD and HT were significantly more induced by TPO compared to N, and (3) this induction depends, in part, on the in vivo thyroid status.

Antithyroid Peroxidase Autoantibodies in Thyroid Diseases*

Thyroid microsomal antibodies (anti-M Ab) have been recently proven to be directed to thyroid peroxidase (TPO). Methods to detect anti-TPO antibodies (anti-TPO Ab) employing purified antigen have been developed, but the available information on the clinical usefulness of this technique is still limited to small patient series. In the present investigation anti-TPO Ab were assayed by a newly developed monoclonal antibody-assisted RIA in a large number (n = 715) of subjects, including 119 normal controls and 596 patients with different autoimmune or nonautoimmune thyroid disease: Anti-TPO Ab were detected in 10 of 119 (8.4%; range, 11-210 U/mL) normal controls, 134 of 181 (74%; range, 11-74.000 U/mL) patients with Graves' disease, all but 1 of 144 (99.3%; range, 11-90.000 U/mL) with Hashimoto's thyroiditis (n - 98) or idiopathic myxedema (n = 46), 20 of 180 (11.1%; range, 11-6.700 U/mL) with miscellaneous nonautoimmune thyroid diseases, 16 of 83 (19.2%; range, 11-6.600 U/mL) patients with differentiated thyroid carcinoma, and in none of 8 patients with subacute thyroiditis. The highest anti-TPO Ab concentrations were found in untreated hypothyroid Hashimoto's thyroiditis, but no simple relationship between anti-TPO Ab levels and thyroid function was observed. Anti-TPO Ab significantly decreased in patients with Graves' disease after treatment with methimazole and in those with hypothyroid Hashimoto's thyroiditis or idiopathic myxedema during L-T4 administration. A highly significant positive correlation (r = 0.979; P less than 0.001) was found between anti-M Ab titers by passive hemagglutination (PH; available in 650 sera) and the corresponding average anti-TPO Ab by RIA; discrepant results were almost exclusively limited to sera with negative or low (1:100-1:400) anti-M Ab titers. Analysis of these discrepant data indicated higher autoimmune disease specificity and sensitivity of anti-TPO Ab RIA tests compared to anti-M Ab by PH. Absorption studies showed that interference of anti-Tg Ab was responsible for anti-M Ab-positive tests in occasional anti-TPO Ab-negative/anti-M Ab-positive sera from autoimmune thyroid disease patients. Anti-TPO Ab determination by RIA was unaffected by circulating thyroglobulin concentrations up to more than 10,000 ng/mL. In conclusion, anti-TPO Ab assay by monoclonal antibody-assisted RIA appears to be more sensitive and specific for thyroid autoimmune diseases than anti-M Ab determination by PH. Since the assay is easy to perform and employs only tracer amounts of purified antigen, these characteristics should allow its rapid diffusion to the clinical routine.

Thyrocyte HLA-DR expression and interferon-gamma production in autoimmune thyroid disease.

We examined the expression of HLA-DR antigen induced by mitogen, mitogen-free supernatants from mitogen-stimulated peripheral blood mononuclear cells (PBMC), or autologous and allogeneic PBMC on thyrocytes cultured for 1-2 weeks (precultured) before the addition of the stimulant. Leucoagglutinin (LAG) and concanavalin A, but not lipopolysaccharide induced HLA-DR expression on thyrocytes from normal subjects (NC) and patients with Graves' disease (GD) and Hashimoto's thyroiditis (HT). The degree of DR expression induced by LAG was significantly less in GD than in NC thyrocytes. This response was dependent on contaminating T cells, especially suppressor-cytotoxic T (Ts/c) cells, NK cells, and HLA-DR+ cells, but not helper-inducer T (Th/i) cells or B cells, in the thyrocyte cultures. OKT3 monoclonal antibody, which activates T cells specifically in the presence of monocytes, also induced thyrocyte HLA-DR expression. Furthermore, interferon-gamma (IFN-gamma) was detected in culture supernatants from LAG-stimulated thyrocytes. Anti-IFN-gamma monoclonal antibody eliminated the ability of LAG to induce HLA-DR. Mitogen-free supernatants from mitogen-stimulated PBMC also induced thyrocyte HLA-DR expression, which was inhibited by anti-IFN-gamma. The supernatants of concanavalin A- or LAG-stimulated PBMC from either untreated or recently treated patients with GD or hypothyroid HT induced less thyrocyte DR expression than NC PBMC. Indeed, the levels of IFN-gamma in supernatants from such patients were lower than those in NC, and the correlation between DR expression and IFN-gamma levels was significant. This IFN-gamma production by PBMC required Th/i cells, NK cells, and HLA-DR+ cells. Before the addition of autologous or allogeneic PBMC, only precultured HT thyrocytes expressed HLA-DR, whereas GD and NC thyrocytes did not. The induction or enhancement of DR expression on autologous thyrocytes by direct coculture with PBMC occurred within 8 days in GD and HT, but not in NC. There was a significant correlation between the serum titer of antithyroid microsomal antibodies and the degree of DR expression. Allogeneic normal PBMC also induced DR expression on NC and GD thyrocytes within 8 days, the effect on the latter being more pronounced than with autologous GD PBMC. Thyrocyte HLA-DR expression induced by autologous GD PBMC and allogeneic normal PBMC required monocytes. Th/i, and NK cells and was blocked by anti-IFN-gamma. However, the enhancement of thyrocyte DR expression by autologous HT PBMC did not require monocytes.(ABSTRACT TRUNCATED AT 400 WORDS)

L-thyroxine therapy induces a fall of thyroid microsomal and thyroglobulin antibodies in idiopathic myxedema and in hypothyroid, but not in euthyroid Hashimoto's thyroiditis.

Thyroid microsomal (MAb) and thyroglobulin (TgAb) antibodies were sequentially measured by sensitive and quantitative radioassays in 17 patients with goitrous Hashimoto's thyroiditis (9 hypothyroid, 8 euthyroid) and in 19 patients with idiopathic myxedema before and at various time intervals up to 24-48 months after the institution of L-thyroxine therapy. Thyroid antibodies were also determined in 5 euthyroid subjects with Hashimoto's thyroiditis maintained without treatment for a similar period. During L-thyroxine administration a reduction of MAb with respect to the pretreatment level was found in 6 of the 9 (67%) hypothyroid patients with Hashimoto's thyroiditis and in 16 of the 19 (84%) patients with idiopathic myxedema. The decrease of MAb was highly significant in both groups (p less than 0.001 and p less than 0.0001, respectively). A fall of TgAb occurred in 2 of the 3 patients (75%) with hypothyroid Hashimoto's thyroiditis and in 9 of the 10 (90%, p less than 0.001) patients with idiopathic myxedema having abnormally elevated pretreatment TgAB levels. No consistent pattern of MAb and TgAb changes was observed in the euthyroid subjects with Hashimoto's thyroiditis, whether treated or untreated. In the hypothyroid patients with Hashimoto's thyroiditis a significant association was found between the decrease of MAb and the reduction of goiter size (p less than 0.05) occurring during L-thyroxine administration. Moreover, the decrease of MAb and TgAb in idiopathic myxedema was greater (p less than 0.05) in the patients with normalized serum TSH (less than or equal to 4 microU/ml) than in those showing only a partial reduction of serum TSH (greater than 4 microU/ml) under L-thyroxine.(ABSTRACT TRUNCATED AT 250 WORDS)

Altered balance of immunoregulatory T lymphocyte subsets in autoimmune thyroid diseases.

Three monoclonal antibodies recognizing cell surface antigens of total peripheral (OKT3), helper/inducer (OKT4) and suppressor/cytotoxic (OKT8) T lymphocytes were used by an indirect immunofluorescence technique to enumerate peripheral T lymphocytes in 25 patients with Graves' disease (including 4 euthyroid Graves' patients), 16 patients with Hashimoto's thyroiditis and 22 normal controls. Total lymphocyte count and percentages of overall T and helper/inducer T cells among peripheral lymphocytes in these conditions showed no significant difference from those of the controls. Percentage of suppressor/cytotoxic T cells, however, was decreased in Graves' disease patients with or without hyperthyroidism. The ratio of helper/inducer T cells to suppressor/cytotoxic T cells was increased in Graves' disease population and slightly increased in hypothyroid Hashimoto's thyroiditis patients. The ratio correlated with the mitogenic response of peripheral mononuclear cells to phytohaemagglutinin, but not with the serum levels of thyroid hormones nor with the titres of thyroid autoantibodies. These findings are in accordance with the results of previous functional studies and indicate possible defects in suppressor T lymphocytes in autoimmune thyroid disease.