The immunogenetics of autoimmune diabetes and autoimmune thyroid disease.

Although medical genetics is a well-developed area of interest, relatively little is known about the diseases caused by the combination of many genes. These multiinfluenced diseases include the autoimmune endocrine diseases. Recent advances in the techniques for whole-genome screening have shown a variety of loci that are linked to the development of insulin-dependent diabetes mellitus, and similar data are likely to be soon generated in autoimmune thyroid disease. Here, the authors survey the current state of genetic knowledge in these two areas and describe the investigative and analytical techniques that are now available. (Trends Endocrinol Metab 1997;8:63-70). (c) 1997, Elsevier Science Inc.

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.

Assay of thyroglobulin in serum with thyroglobulin autoantibodies: an unobtainable goal?

Measurement of thyroglobulin (Tg) in serum with anti-Tg autoantibodies (TgAb) represents a difficult challenge. Immunoradiometric assays (IRMA) employing monoclonal anti-Tg antibodies not cross-reacting with endogenous TgAb have recently been developed and proposed for Tg assays in TgAb-positive sera. The aim of the present investigation was to assess the clinical reliability of this approach. Assays of serum Tg in patients with and without TgAb using one such monoclonal antibody IRMA (Thyroglobulin IRMA-Pasteur; IRMA-1) were compared with those obtained by a conventional IRMA employing polyclonal anti-Tg antibodies (HTGK-Sorin; IRMA-2). Preliminary studies for assessment of the interference of TgAb showed that the recovery of added Tg was significantly higher (P < 0.01) when determined by IRMA-1 (64.6 +/- 23%) than by IRMA-2 (49.5 +/- 20%). Study groups included 79 patients with differentiated thyroid carcinoma (DTC) treated by total thyroidectomy and radioiodine ablation; 24 had no metastases or residual thyroid tissue, 31 had a thyroid residue, and 24 had metastatic disease. Seventy-five patients with autoimmune thyroid disease (47 with Graves' and 28 with Hashimoto's disease) were also included. In TgAb-negative sera from DTC patients, similar Tg concentrations were found by both IRMA, i.e. undetectable in most patients with no residual thyroid or neoplastic tissue, low to moderately elevated in the majority of those with residual thyroid tissue, and markedly elevated in all patients with metastatic disease. Serum Tg was undetectable by both assays in several TgAb-positive sera from DTC patients with residual thyroid tissue or metastatic disease, respectively, in whom a detectable or even high serum Tg concentration was expected. Despite the lower in vitro interference of TgAb in IRMA-1, there was no difference between the two assays. In the group of patients with thyroid autoimmune disease, serum Tg concentrations were found to be high in TgAb-negative sera and much lower in TgAb-positive sera by both IRMAs. In conclusion, the present study demonstrates that the use of a monoclonal antibody IRMA for serum Tg, although less susceptible to in vitro TgAb interference, does not necessarily provide any substantial advantage with respect to a conventional polyclonal IRMA in detecting Tg in TgAb-positive sera. The finding of undetectable or lower than expected serum Tg by either method in TgAb-positive serum may well reflect a truly reduced serum Tg concentration. This might be due to an accelerated Tg metabolic clearance in the presence of TgAb.(ABSTRACT TRUNCATED AT 400 WORDS)

Linkage analysis of candidate genes in autoimmune thyroid disease. III. Detailed analysis of chromosome 14 localizes Graves' disease-1 (GD-1) close to multinodular goiter-1 (MNG-1). International Consortium for the Genetics of Autoimmune Thyroid Disease.

The autoimmune thyroid diseases [Graves' and Hashimoto's diseases (GD and HT)] develop in genetically susceptible individuals, but the genes responsible for this susceptibility remain unknown. To identify such genes, we have been testing candidate genes and chromosomal regions using highly polymorphic microsatellite markers. We recently reported evidence for the first locus linked to GD (GD-1) on chromosome 14q31 in a small group of families. We have now extended these studies and analyzed 53 multiplex families with GD and/or HT (323 individuals). Chromosome 14 was screened using 16 microsatellite markers spanning the entire chromosome. Three additional markers located inside candidate genes on chromosome 14 were also studied. Microsatellite markers were amplified using fluorescent-labeled primers and separated on an ABI-310 genetic analyzer. The data were analyzed using LIPED software for two-point logarithm of odds (LOD) score analysis and GeneHunter software for multipoint linkage analysis. No linkage of any marker was found to HT or autoimmune thyroid diseases (GD+HT). The previously identified GD-1 locus on 14q31 continued to show evidence of linkage to GD in this much larger set of families. The maximum LOD score was 2.1 obtained for marker D14S81 (theta=0.01), assuming a recessive mode of inheritance and a penetrance of 0.3. Multipoint analysis yielded a maximum LOD score of 2.5 between markers D14S81 and D14S1054. There was no evidence for heterogeneity in our sample. These data again suggest the presence of a major Graves' disease susceptibilitygene (GD-1) on chromosome 14q31. This locus is close to the recently identified multinodular goiter-1 locus.

Linkage analysis of candidate genes in autoimmune thyroid disease. II. Selected gender-related genes and the X-chromosome. International Consortium for the Genetics of Autoimmune Thyroid Disease.

Hashimoto's thyroiditis (HT) and Graves' disease (GD) are autoimmune thyroid diseases (AITD) in which multiple genetic factors are suspected to play an important role. Until now, only a few minor risk factors for these diseases have been identified. Susceptibility seems to be stronger in women, pointing toward a possible role for genes related to sex steroid action or mechanisms related to genes on the X-chromosome. We have studied a total of 45 multiplex families, each containing at least 2 members affected with either GD (55 patients) or HT (72 patients), and used linkage analysis to target as candidate susceptibility loci genes involved in estrogen activity, such as the estrogen receptor alpha and beta and the aromatase genes. We then screened the entire X-chromosome using a set of polymorphic microsatellite markers spanning the whole chromosome. We found a region of the X-chromosome (Xq21.33-22) giving positive logarithm of odds (LOD) scores and then reanalyzed this area with dense markers in a multipoint analysis. Our results excluded linkage to the estrogen receptor alpha and aromatase genes when either the patients with GD only, those with HT only, or those with any AITD were considered as affected. Linkage to the estrogen receptor beta could not be totally ruled out, partly due to incomplete mapping information for the gene itself at this time. The X-chromosome data revealed consistently positive LOD scores (maximum of 1.88 for marker DXS8020 and GD patients) when either definition of affectedness was considered. Analysis of the family data using a multipoint analysis with eight closely linked markers generated LOD scores suggestive of linkage to GD in a chromosomal area (Xq21.33-22) extending for about 6 cM and encompassing four markers. The maximum LOD score (2.5) occurred at DXS8020. In conclusion, we ruled out a major role for estrogen receptor alpha and the aromatase genes in the genetic predisposition to AITD. Estrogen receptor beta remains a candidate locus. We found a locus on Xq21.33-22 linked to GD that may help to explain the female predisposition to GD. Confirmation of these data in HT may require study of an extended number of families because of possible heterogeneity.

Linkage analysis of candidate genes in autoimmune thyroid disease: 1. Selected immunoregulatory genes. International Consortium for the Genetics of Autoimmune Thyroid Disease.

Graves' and Hashimoto's diseases are autoimmune thyroid diseases in which the genetic contribution is complex. For this reason, identification of necessary susceptibility genes has been difficult. However, a number of immunoregulatory genes have been implicated by association studies, including: CTLA-4, a recently described protein involved in antigen presentation, located on chromosome 2q33; the T-cell receptor V alpha and V beta gene complexes, located on 14q11 and 7q35, respectively; and the Ig gene complex (IgH), located on 15q11. We used polymorphic microsatellite markers located within these genes, or gene complexes, to test for linkage (rather than association), to each of these candidates. Using markers within the loci allowed us to assume a fixed recombination fraction of 0.01 in the tested model. Three hundred eight subjects from 48 multiplex families were studied, with 142 affected subjects. Using this set of families, we have previously shown evidence of linkage with a major susceptibility locus for Graves' disease (GD-1) on 14q24.3-31, with a maximum lod (logarithm + odds) score of 2.1, at a penetrance of 80% and with a dominant mode of inheritance. In the present study, we obtained consistently negative lod scores for each of the candidate genes, assuming either dominant or recessive modes of inheritance. These data, therefore, showed evidence against linkage with all the candidate genes. Unlike association studies, linkage analyses detect major genetic influences on disease susceptibility exerted by the linked loci. The lack of linkage for the immunoregulatory genes that were studied indicated, therefore, that they were not major contributors to disease etiology.

Mapping the major susceptibility loci for familial Graves' and Hashimoto's diseases: evidence for genetic heterogeneity and gene interactions.

The autoimmune thyroid diseases (AITDs), comprising Graves' disease (GD) and Hashimoto's thyroiditis (HT), appear to develop as a result of a complex interaction between predisposing genes and environmental triggers. The goals of the present study were to identify the susceptibility loci for GD and HT and to study the relationships between them. We performed a whole genome linkage study on a dataset of 56 multiplex, multigenerational AITD families (354 individuals), using 387 microsatellite markers. We identified 6 loci that showed evidence for linkage to AITD. Only one locus, on chromosome 6 [AITD-1; 80 centimorgans (cM)], was linked with both GD and HT [maximum LOD score (MLS), 2.9]. This locus was close to, but distinct from, the human leukocyte antigen region. One locus on chromosome 13 (HT-1; 96 cM) was linked to HT (MLS, 2.1), and another locus on chromosome 12 (HT-2; 97 cM) was linked to HT in a subgroup of the families (MLS, 3.8). Three loci showed evidence for linkage with GD: GD-1 on chromosome 14 (99 cM; MLS, 2.5), GD-2 on chromosome 20 (56 cM; MLS, 3.5), and GD-3 on chromosome X (114 cM; MLS, 2.5). Since GD-2 showed the strongest evidence for linkage to GD we fine-mapped this locus to a 1-cM interval between markers at 55 and 56 cM on chromosome 20. These results demonstrated that 1) Graves' and Hashimoto's diseases are genetically heterogeneous, with only one locus in common to both diseases on chromosome 6; 2) only one HT locus was identified in all families, probably due to heterogeneity of the HT phenotype; and 3) three loci were shown to induce genetic susceptibility to GD by interacting with each other. One of them (GD-2) was fine-mapped to a 1-cM interval.

A novel mutation of the autoimmune regulator gene in an Italian kindred with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy, acting in a dominant fashion and strongly cosegregating with hypothyroid autoimmune thyroiditis.

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy is a rare autosomal recessive disorder characterized by hypoparathyroidism, adrenal failure, chronic mucocutaneous candidiasis, and ectodermal dystrophies and other organ-specific autoimmune diseases. Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy is caused by mutations of the autoimmune regulator gene. We identified an Italian family with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy and a pattern of inheritance suggestive of a dominant mechanism. Serological and clinical studies showed a high prevalence of hypothyroid autoimmune thyroiditis in affected members with classical autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy. Direct sequencing of the entire coding region of the autoimmune regulator gene revealed the presence in the proband of a novel missense (G228W) mutation in exon 6 in a heterozygous state. The same heterozygous mutation was identified in all family members with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy and/or hypothyroid autoimmune thyroiditis. None of the unaffected family members and 50 unrelated Italian controls carried the mutation. In contrast with all other autoimmune regulator mutations reported in families, the novel G228W mutation acts in a dominant fashion in our family, as only one heterozygous mutation was found in the entire coding sequence of the autoimmune regulator gene in the proband. Moreover, analysis of the family tree showed direct transmission of the hypothyroid autoimmune thyroiditis/polyendocrinopathy-candidiasis-ectodermal dystrophy phenotype to the offspring in each generation in the absence of consanguinity, further supporting a dominant inheritance. The G228W closely cosegregated with hypothyroid autoimmune thyroiditis in our family, whereas a low penetrance of the full autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy phenotype was observed. In conclusion, we report a novel mutation of the autoimmune regulator gene in a family with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy, closely cosegregating with hypothyroid autoimmune thyroiditis. The G228W mutation acts in a dominant fashion and may shed light on the structure-function relationship of the autoimmune regulator protein.

Mapping of a major susceptibility locus for Graves' disease (GD-1) to chromosome 14q31.

The autoimmune thyroid diseases (AITD), encompassing Graves' disease (GD) and Hashimoto's thyroiditis (HT), occur in genetically susceptible individuals. In order to identify the AITD susceptibility genes, we have studied DNA markers in the regions of 8 candidate genes: (1) the HLA region, (2) the TSH receptor, (3) thyroid peroxidase, (4) thyroglobulin, (5) IDDM-4, (6) IDDM-5, (7) Immunoglobulin heavy chain gene and (8) CTLA-4. One hundred and seven subjects from 19 informative families were studied, 14 subjects had GD and 32 subjects had HT. LOD scores were maximized assuming both dominant and recessive modes of inheritance. No linkage was found for any marker in patients with HT. In patients with GD, negative LOD scores were obtained for all the candidate genes, except for markers in the TSH receptor region on chromosome 14q31. Positive LOD scores were found for several markers on 14q31. Marker D14S81 gave the highest score (Z max = 2.05, theta = 0.01) assuming a dominant mode of inheritance and a penetrance of 0.8. These data confirm our previous observations of a lack of a necessary disease locus for AITD in the HLA gene region. Further, the data suggest the presence of an important susceptibility gene on 14q31 but at a considerable distance from the TSH receptor gene.

CTLA-4 and not CD28 is a susceptibility gene for thyroid autoantibody production.

One of the hallmarks of the human autoimmune thyroid diseases (AITDs) is the production of high titers of autoantibodies against thyroglobulin and thyroid peroxidase that often precedes the development of clinical disease. A high percentage of family members of patients with AITDs have significant titers of thyroid antibodies (TAbs), suggesting a genetic predisposition for their development, and segregation analyses have favored a dominant mode of inheritance. The aim of the present study was to identify the susceptibility genes for TAb production. We completed a genome-wide scan in 56 multiplex families (323 individuals) in which all family members with AITDs and/or detectable TAbs were considered affected. The highest 2-point logarithm of odds (LOD) score of 3.6 was obtained for marker D2S325 on chromosome 2q33 at 210.9 centimorgans. This locus showed no evidence for linkage to Graves' disease or Hashimoto's thyroiditis (2-point LOD scores, 0.42 for Graves' disease and -0.60 for Hashimoto's thyroiditis), demonstrating that the gene in this region conferred susceptibility to TAbs, but that clinical disease development required additional genetic and/or environmental factors. We then fine-mapped the region linked with TAbs using 11 densely spaced microsatellite markers. Multipoint linkage analysis using these markers showed a maximum LOD score of 4.2 obtained for marker D2S155 at 209.8 centimorgans (with heterogeneity, alpha = 0.41). As the linked region contained the CTLA-4 and CD28 genes, we then tested whether they were the susceptibility genes for TAbs on chromosome 2q33. The CD28 gene was sequenced in 15 individuals, and a new C/T single nucleotide polymorphism (SNP) was identified in intron 3. Analysis of this SNP revealed no association with TAbs in the probands of the linked families (families that were linked with D2S155) compared with controls. The CTLA-4 gene was analyzed using the known A/G(49) SNP, and the results showed a significantly increased frequency of the G allele in the probands of the linked families compared with the probands of the unlinked families or with controls (P = 0.02). We concluded that 1) a major gene for thyroid autoantibody production was located on chromosome 2q33; 2) the TAb gene on chromosome 2q33 was most likely the CTLA-4 gene and not the CD28 gene; and 3) CTLA-4 contributed to the genetic susceptibility to TAb production, but there was no evidence that it contributed specifically to Graves' or Hashimoto's diseases.

Complex alteration of thyroid function in healthy centenarians.

Several changes in thyroid function have been described in the elderly and largely attributed to concomitant nonthyroidal illness. The extent to which aging per se contributes to these changes remains to be elucidated, and scanty data are available in extremely old subjects. The present study was designed to focus on thyroid function during physiological aging, taking advantage of two groups of selected aged individuals: group A of healthy centenarians (n = 41; age range, 100-110 yr) and group B including healthy elderly subjects selected by the criteria of the EURAGE SENIEUR protocol (n = 33; age range, 65-80 yr). Control groups included 98 healthy normal adult subjects (group C; age range, 20-64 yr) and 52 patients with miscellaneous nonthyroidal illness (group D; age range, 28-82 yr). Our previous report of a low prevalence of thyroid autoantibodies in centenarians was confirmed and extended by the finding of a similar low autoantibody prevalence in the highly selected healthy elderly population of group B. Subclinical primary hypothyroidism was found in 3 (7.3%) centenarians, and their data were excluded from further statistical evaluation. No significant difference was found in the median serum free T4 levels of groups A-C. Median (and range) serum free T3 (FT3) was lower in centenarians [3.67 pmol/L (2.3-5.5)] than in group B [5.22 pmol/L (3.4-6.1)] and group C [5.38 pmol/L (2.9-8.4); P < 0.0001 vs. both groups]. Similarly, the median serum TSH level of centenarians [0.97 mU/L (< 0.09 to 2.28)] was lower than those in groups B [1.17 mU/L (0.53-2.74)] and C [1.7 mU/L (0.4-4.8); P < 0.0001 vs. both groups]; moreover, serum TSH was also significantly (P < 0.01) lower in group B than in group C. Both serum FT3 and TSH concentrations showed a significant inverse correlation (r = -0.634; P < 0.0001 and r = -0.377; P < 0.0001, respectively) with age. Median serum FT3 in centenarians was lower than that in group D patients [4.61 pmol/L (2.15-6.6); P < 0.0001]. In contrast, median serum rT3 in centenarians [0.40 nmol/L (0.20-0.77)], although higher than those in groups B [0.24 nmol/L (0.15-0.37); P < 0.0001] and C [0.22 nmol/L (0.05-0.46); P < 0.0001], was significantly lower than that in group D [0.60 nmol/L (0.13-2.08); P < 0.0001]. In conclusion, thyroid function appears to be well preserved until the eighth decade of life if healthy subjects are studied, whereas a reduction of serum FT3 is observed in extreme aging.(ABSTRACT TRUNCATED AT 400 WORDS)

Mild clinical expression of myasthenia gravis associated with autoimmune thyroid diseases.

Myasthenia gravis (MG) may occur in association with autoimmune thyroid diseases (AITD). The aim of this study was to evaluate the features of MG associated with AITD compared to those of MG without AITD. A total of 129 MG patients (34 men and 95 women; age range, 11-81 yr) were subdivided into: group A, 56 MG patients with AITD [25 with autoimmune thyroiditis and 31 with Graves' disease (GD)]; group B, 21 MG patients with nonautoimmune thyroid diseases; and group C, 52 MG patients without thyroid disease. The severity of MG was ranked according to the Osserman score. Laboratory evaluation included assays for antithyroid and antiacetylcholine receptor (AchRAb) antibodies. Ocular MG (Osserman's class 1) was more frequent in group A (41.0%) than in group B (14.2%; P < 0.03) or C (21.4%; P < 0.03). Severe generalized MG (classes > or = 2B) was more frequent in groups B (57.1%; P < 0.03) and C (51.9%; P < 0.02) than in group A (28.5%). GD patients with clinical evidence of ophthalmopathy had a higher frequency (P = 0.05) of ocular MG (57.8%) than GD patients without clinical ophthalmopathy (16.6%). Thymic disease was less frequent in group A (26.7%) than in group B (71.4%; P = 0.001) or C (59.7%; P = 0.001). The prevalence of thymic hyperplasia was 17.8%, 38.0%, and 40.3% in groups A, B, and C, respectively; the prevalence of thymoma was 8.9%, 33.4%, and 19.4%. When only patients with generalized MG were considered, thymic disease was less frequent (P < 0.02) in group A (40.6%) than in the remaining groups (69.4%). AchRAb was more frequent in groups B (57.1%) and C (57.6%; P < 0.03) than in group A (35.7%). In conclusion, MG associated with AITD has a mild clinical expression, with preferential ocular involvement and lower frequency of thymic disease and AchRAb. This supports the hypothesis that ocular and generalized MG are separate diseases with different spectra of associated diseases. Nonautoimmune thyroid diseases have no influence on the features of MG. The association of ocular MG and AITD might be due to a common autoimmune mechanism and/or a peculiar genetic background.

Comparison of the effectiveness and tolerability of intravenous or oral glucocorticoids associated with orbital radiotherapy in the management of severe Graves' ophthalmopathy: results of a prospective, single-blind, randomized study.

Eighty-two consecutive patients with moderate-to-severe and active Graves' ophthalmopathy were randomly treated with orbital radiotherapy combined with either oral (prednisone; starting dose, 100 mg/d; withdrawal after 5 months) or iv (methylprednisolone; 15 mg/kg for four cycles and then 7.5 mg/kg for four cycles; each cycle consisted of two infusions on alternate days at 2-wk intervals) glucocorticoids. The two groups did not differ for age, gender, duration of hyperthyroidism and ophthalmopathy, prevalence of smokers, thyroid volume, and pretreatment ocular conditions. Both groups of patients received radioiodine therapy shortly before treatment for Graves' ophthalmopathy. Follow-up lasted for 12 months. A significant reduction in proptosis (from 23.2 +/- 3.0 to 21.6 +/- 1.2 mm in the iv glucocorticoid group, P < 0.0001; and from 23 +/- 1.8 to 21.7 +/- 1.8 mm in oral glucocorticoid group, P < 0.0001) and in lid width (from 13.3 +/- 2.5 to 11.8 +/- 2.2 mm, and from 13.6 +/- 2.0 to 11.5 +/- 1.9 mm, respectively; P < 0.001 in both cases) occurred, with no difference between the two groups. Diplopia significantly improved in both groups: it disappeared in 13 of 27 (48.1%) iv glucocorticoid patients (P < 0.005) and in 12 of 33 (36.4%) oral glucocorticoid patients (P < 0.03). The degree of amelioration of diplopia did not significantly differ between the two groups (P = 0.82). Optic neuropathy improved in 11 of 14 iv glucocorticoid (P < 0.01) and only in 3 of 9 oral glucocorticoid (P = 0.57) patients, with no significant difference in these outcomes. The Clinical Activity Score decreased from 4.5 +/- 1.2 to 1.7 +/- 1.0 (P < 0.0001) in the iv glucocorticoid group and from 4.2 +/- 1.1 to 2.2 +/- 1.2 (P < 0.0001) in the oral glucocorticoid group; final Clinical Activity Score was significantly lower in iv glucocorticoid than in oral glucocorticoid patients (P < 0.01). By self-assessment evaluation, 35 (85.3%) iv glucocorticoid and 30 (73.2%) oral glucocorticoid patients reported an improvement of ocular conditions (P = 0.27). Overall, both treatments produced favorable effects in most patients, but responders in the iv glucocorticoid group (36 of 41, 87.8%) were more than in the oral glucocorticoid group (26 of 41, 63.4%) (P < 0.02). Moreover, iv glucocorticoid treatment was better tolerated than oral glucocorticoid treatment. Side effects occurred in 23 (56.1%) iv glucocorticoid and 35 (85.4%) oral glucocorticoid patients (P < 0.01); in particular, cushingoid features developed in 5 of the former and 35 of the latter patients. One iv glucocorticoid patient had severe hepatitis of undetermined origin at the end of glucocorticoid treatment, followed by spontaneous recovery. In conclusion, high-dose iv glucocorticoid and oral glucocorticoid (associated with orbital radiotherapy) are effective in the management of severe Graves' ophthalmopathy, but the iv route seems to be more effective and better tolerated than the oral route and associated with a lower rate of side effects.

The genetics of Hashimoto's disease.

Despite strong epidemiologic evidence in favor of a genetic component in the etiology of HT, few hereditary risk factors have been consistently identified. These factors include the HLA and CTLA-4 genes. The mechanisms by which these genes confer increased susceptibility to HT are unclear. The identification of these genes has failed to explain completely the large hereditary effect observed in families of patients. More substantial genetic determinants must be hidden in the folds of the human genome and will most likely be detected in the near future. The powerful approach of linkage analysis will be supported by advancements in the description of the human genome and by technologic improvements in the ability to process large amounts of biologic data. Knowledge of such determinants will provide predictive tools to be used on clinical grounds and invaluable insight into the pathogenesis of this puzzling disease.

T-cell receptors and autoimmune thyroid disease--signposts for T-cell-antigen driven diseases.

The human autoimmune thyroid diseases (AITDs) are characterized by profuse infiltrates of both CD4+ and CD8+ T cells. The intrathyroidal T-cell-receptor repertoire in Graves' disease, more than in Hashimoto's disease, has been shown to be biased as evidenced by phenotypic analysis and by the use of a restricted T-cell-receptor variable (V) gene repertoire seen in both TCR alpha and beta chains. Evidence for a bias in the T-cell repertoire has also been observed in animal models of induced and spontaneous autoimmune thyroiditis. We found a similar phenomenon of autoimmune thyroid-related T-cell bias in thyroid-humanized scid mice. In these studies we transplanted lymphocyte-depleted thyrocytes and autologous peripheral lymphocytes from AITD patients with a basement membrane preparation which allowed the formation of an artificial thyroid which we have called an "organoid". T-cell clonal expansion was present in these artificial mixed-cell organoids which appeared to mimic the in vivo process. Such clonal expansion was suggestive of an antigen-driven immune response and could also be identified in thyroid tissue from patients with Graves' disease. Our data on scid mice grafted with human mixed-cell thyroid organoids, therefore, suggested that the major antigens driving T-cell selection in patients with AITD were most likely to be thyroid specific. These antigens include thyroglobulin, thyroid peroxidase, and the receptor for thyroid stimulating hormone (TSHR) on the surface of thyroid epithelial cells and we found significant T-cell proliferation to synthetic TSHR peptides in patients with AITD as compared with normals. Our search for a TCR recognition motif for the autoantigen TPO did not reveal any specific sequence motifs. Instead, analysis of the physico-chemical characteristics i.e. hydrophobicity of the amino acids in the CDR3 (N) region of the TCR alpha chain, revealed a strong negative linear correlation between strength of stimulation and the average hydrophobicity of N-region amino acids. This led us to hypothesize that lower affinity T-cell clones were commonly more hydrophobic in their CDR3 alpha region amino acids in keeping with potential crossreactivity of such T cells as a consequence of promiscuous, hydrophobic CDR3 regions. This phenomenon would be analogous to polyreactive, natural autoantibodies which tend to be crossreactive and 'sticky'. Thus, the physico-chemical characteristics of the TCR alpha CDR3 region supported the interaction with antigen/MHC by potentially cross-reactive T cells of low affinity. It would seem likely that such low-affinity autoreactive T-cell populations serve as a pool of potentially pathogenetic cells. These cells would be able to respond to an insult which, via a number of possible mechanisms such as molecular mimicry, would initiate a thyroid lymphocytic infiltration in an antigen-driven fashion with intrathyroidal T-cell expansion and a marked bias in the utilization of T-cell-receptor V genes.

False negative results observed in anti-thyroid peroxidase autoantibody determination by competitive radioimmunoassays using monoclonal antibodies.

OBJECTIVE: Anti-thyroid peroxidase autoantibody (anti-TPO) and anti-thyroid microsomal antibody (anti-M) are strictly related, but discrepancies are sometimes observed. The aim of this study was to assess the incidence and to identify the causes of these discrepancies. DESIGN AND ANTIBODY MEASUREMENTS: Anti-M by passive hemagglutination and anti-TPO by two competitive monoclonal antibody-assisted radioimmunoassays (RIA-1 and RIA-2) were measured in 10,103 sera from 4232 subjects (663 male, 3569 female) screened for thyroid disease. RESULTS: Anti-TPO and anti-M correlated quite well (r = 0.7 and p < 0.0001 by RIA-1: r = 0.74 and p < 0.0001 by RIA-2), with discrepancies mostly limited to sera with low antibody titers. After exclusion of the latter samples, anti-TPO were detected in only 79 (1.4%) out of 5317 anti-M negative sera, but were undetectable in a more consistent proportion (130/2880 = 4.5%) of sera from patients with autoimmune thyroid disease and positive anti-M. In 61 sera of the latter group, anti-TPO was measured by a non-competitive RIA (RIA-3). Forty-one (67.7%) were positive by RIA-3, suggesting the presence of anti-TPO not competing with the monoclonal antibodies of RIA-1 and RIA-2. The remaining 20 sera had undetectable anti-TPO also by RIA-3. Nineteen (95%) of these sera had positive anti-thyroglobulin (anti-Tg) autoantibody and preincubation with thyroglobulin inhibited the agglutination reaction of anti-M tests. CONCLUSION: Anti-TPO by competitive monoclonal antibody-assisted RIA is negative in a minority of sera of patients with autoimmune thyroid disease and positive anti-M. This could be accounted for by anti-Tg producing false positives in the anti-M assay and by a subset of anti-TPO not competing with the monoclonal antibodies in the RIA. When autoimmune thyroid disease is suspected on clinical grounds, a negative anti-TPO test with a competitive RIA should be confirmed always by a non-competitive assay.

Increased frequency of euthyroid ophthalmopathy in patients with Graves' disease associated with myasthenia gravis.

We previously showed that myasthenia gravis (MG) has a mild clinical expression when associated with autoimmune thyroid diseases (AITD). In the present study we have investigated the frequency of thyroid-associated ophthalmopathy (TAO) in patients with Graves' disease (GD) associated with MG as compared with GD patients without MG. A total of 418 patients with GD were studied, 31 with MG and 387 without MG. TAO was evaluated by physical examination, exophthalmometry, computerized tomography, and computerized visual fields assessment. The overall prevalence of TAO was similar in GD patients with MG (61.2%) and in those without MG (56.4%). When the analysis was restricted to GD patients with ocular MG, a greater frequency of TAO was found (84.6%), compared with GD patients without MG or with GD patients with generalized MG, although the differences did not reach the statistical significance. GD patients with MG had a significantly greater prevalence (12.9%) of euthyroid ophthalmopathy (clinically overt ophthalmopathy without previous and/or current hyperthyroidism) than those without MG (3.1%; p = 0.003). The results suggest a preferential association between the ocular manifestations of GD and MG, which may be due to immunological cross-reactivity against common autoimmune targets in the eye muscle as well as to a common genetic background.

Limited genetic susceptibility to severe Graves' ophthalmopathy: no role for CTLA-4 but evidence for an environmental etiology.

Graves' disease (GD) is an autoimmune thyroid disease (AITD) characterized by hyperthyroidism and by the occurrence of a distinctive ophthalmopathy (orbitopathy), which presents with varying degrees of severity. Graves' disease clusters in families but the importance of heredity in the pathogenesis of the associated ophthalmopathy is unclear. We have studied the family history of 114 consecutive, ethnically mixed patients with severe Graves' ophthalmopathy (GO). Patients were selected by unambiguous single ascertainment. Seventy-seven percent of patients were female and 59% smoked. The mean age at onset of their GD was 43 years (range 17-78 years). Forty-one patients (36%) had a family history of AITD, defined as a first- and/or a second-degree relative affected with either Graves' disease (GD) or Hashimoto's thyroiditis (HT). The segregation ratio for AITD in nuclear families in our ascertained Graves' ophthalmopathy families was 0.07 (0.12 in Caucasians only). Hence, the higher prevalence of AITD among relatives of Graves' ophthalmopathy patients agreed with the known genetic predisposition to AITD and this predisposition was stronger in women than in men. However, only 3 of the 114 patients had a family history of severe Graves' ophthalmopathy (all second-degree relatives) and the segregation ratio for GO was 0. These data did not support a major role for familial factors in the development of severe Graves' ophthalmopathy distinct from Graves' disease itself. In addition, we tested 4 candidate genes, human leukocyte antigen (HLA), tumor necrosis factor-beta (TNF-beta), CTLA-4 and the thyrotropin receptor (TSHR), for association with Graves' ophthalmopathy. These were negative except for the HLA and CTLA-4 genes, which were found to be weakly associated with GO giving similar relative risk (RR) as in GD patients without ophthalmopathy. These data suggested that environmental factors, rather than major genes, were likely to predispose certain individuals with AITD to severe Graves' ophthalmopathy. Smoking remains one example of such potential external insults.

[Radiometabolic therapy of the autonomous thyroid nodule]. / Terapia radiometabolica del nodulo tiroideo autonomo.

The aim of this paper is to synthetically focus on current views on the use of radioiodine for the treatment of hyperthyroidism in single autonomously functioning thyroid nodules (AFN). Radioiodine administration represents a simple and effective alternative to surgical ablation of AFN, especially in elderly patients with small nodules (< 3 cm diameter). Radioiodine is very selectively accumulated in the thyroid, where it can deliver its energy without virtually affecting any other organ. Since its first use in 1942, 131I is (as Na131I) still the radioisotope of choice, due to easy availability and to its peculiar physical characteristics. These include a short half-life (8 days) and a spectrum of radiation (mainly of the beta type) with an optimal energy delivery in the nodule and with low penetration in the surrounding tissue. The effectiveness of radioiodine administration in permanently correcting hyperthyroidism in AFN has been demonstrated in many studies and may reach 80% with a single dose administration. The optimal dose has not been completely defined, but may be empirically calculated taking into account the weight of the nodule (evaluated by scintiscan or ultrasound) and the radioiodine uptake after 24 hours. In our and in many other institutions, indications to radioiodine treatment are currently the following: age > 35-40 years, diameter of the nodule < 3 cm and/or serious general diseases contraindicating surgical treatment. The only absolute contraindication to radioiodine treatment is pregnancy, due to the possible mutagenic effects on the foetus and to the extreme sensitivity of the foetal thyroid to radioiodine after the 10th week of gestation.(ABSTRACT TRUNCATED AT 250 WORDS)

Thyroiditis: clinical aspects and diagnostic imaging.

Thyroiditis belongs to a heterogeneous group of inflammatory thyroid diseases. Hashimoto's thyroiditis, has an autoimmune pathogenesis: patients can be euthyroid or develop hypothyroidism, but may also experience transient thyrotoxicosis. Silent and postpartum thyroiditis also recognize an autoimmune origin; their clinical course being characterized by transient thyrotoxicosis occurring either sporadically or post-partum. Subacute thyroiditis is a painful, inflammatory disease of viral origin. Acute thyroiditis is a rare, serious, bacterial inflammatory disease. Riedel's thyroiditis is a rare chronic inflammatory disorder of unknown etiology, characterized by dense thyroid fibrosis. A diffuse thyroid hypoechogenicity is the hallmark of Hashimoto's thyroiditis, due to extensive lymphocytic infiltration of the gland. In postpartum and silent thyroiditis a diffuse or multifocal hypoechogenicity is found, while subacute thyroiditis is characterized by multiple ill-defined and migrating hypoechogenic areas. Both in acute and Riedel's thyroiditis there is marked hypoechogenicity.