Detection of thyroid growth immunoglobulins (TGI) by [3H]-thymidine incorporation in cultured rat thyroid follicles

The phenotype of newly diagnosed Graves' disease in Italy in recent years is milder than in the past: results of a large observational longitudinal study

OBJECTIVE

The Merseburg triad (hyperthyroidism, goiter, and orbitopathy) characterizes classical description of Graves' disease (GD). Aim of this observational, longitudinal study was to evaluate the current clinical features of newly diagnosed GD in Italy.

MATERIALS AND METHODS

In two Northern Italy centers (Varese and Pavia), 283 consecutive patients (211 women, 72 men; mean age 47.4 years) with newly diagnosed GD were recruited in the years 2010-2014. Diagnosis was based on established criteria, and thyroid volume was assessed by ultrasonography. A clinical severity score (CSS) to assess the overall disease severity was developed by grading each component of the Merseburg triad.

RESULTS

At diagnosis, 45 % of patients had no goiter, and 30 % had a small goiter. The proportion of goitrous patients was much lower than in two Italian studies performed 20-30 years ago. Hyperthyroidism was subclinical in 16 % and mild in 29 % of patients, and Graves' orbitopathy was present in 20 %, usually mild, and active in only 2.5 % of patients. Using the CSS, less than half (44 %) of the patients had severe GD, while 22 % had mild and 34 % moderate disease. CSS was associated with a significantly higher risk of poorly controlled hyperthyroidism at 6 months.

CONCLUSIONS

In Italy, a relevant proportion of Graves' patients at diagnosis have mild to moderate GD; about half of them have no goiter, slightly less than one-fifth have subclinical hyperthyroidism, and only 20 % have GO. Thus, the clinical phenotype of GD is milder than in the past, possibly due to both earlier diagnosis and treatment, and improved iodine nutrition.

Growth stimulating antibodies in endemic goitre: a reappraisal

OBJECTIVE

Previous studies, using a variety of methods, have reported growth-promoting immunoglobulins (IGs) in a large proportion of patients with endemic goitre. We sought to determine whether thyroid growth-promoting immunoglobulins (TGI) are present in the serum of Indian patients with endemic goitre.

DESIGN

IgG was prepared by protein G-Sepharose affinity purification and added to FRTL-5 thyroid cells in the presence of suboptimal concentrations of TSH.

PATIENTS

We studied 30 sequential patients with endemic goitre and 16 euthyroid controls without a goitre from the same area.

MEASUREMENTS

Two assays for thyroid cell growth were used: 3H-thymidine incorporation, and flow cytometric measurement of the proportion of cells in the S phase and G2/M phase of the cell cycle.

RESULTS

Both assays were shown to detect growth produced by TSH and by thyroid stimulating antibodies in IgG preparations from 3 patients with Graves' disease. There was no significant increase in either 3H-thymidine incorporation or the distribution of cells in S or G2/M phase with IgGs from endemic goitre patients, and no difference between the effects of these IgGs and those from the normal subjects.

CONCLUSIONS

Thyroid growth-promoting immunoglobulins cannot be detected in Indian patients with endemic goitre.

The effect of treatment with levothyroxine or iodine on thyroid size and thyroid growth stimulating immunoglobulins in endemic goitre patients

OBJECTIVE

We assessed the effect of levothyroxine or iodine on thyroid size and on thyroid growth stimulating immunoglobulins in endemic goitre patients.

DESIGN

Levothyroxine or iodine was given orally in an open randomized prospective study (100 and 200 micrograms respectively).

PATIENTS

Thirty-seven euthyroid patients with diffuse iodine deficiency goitres and thyroid growth stimulating immunoglobulins were studied.

MEASUREMENTS

Thyroid size, thyroid growth stimulating immunoglobulins (mitosis arrest assay), basal TSH, free T3, free T4, thyroid anti-microsomal antibodies, antithyroglobulin antibodies, anti-TSH receptor antibodies and urinary iodine excretion were measured.

RESULTS

Thyroid size decreased significantly in both groups, in the levothyroxine group more than in the iodine treated group. Thyroid growth stimulating immunoglobulins levels also decreased significantly in both groups. Between groups there was no statistically significant difference. A statistically significant correlation between thyroid growth stimulating immunoglobulins reduction profiles and goitre size reduction could not be established. TSH levels became suppressed in the levothyroxine group while the T4 values rose; in the iodine treated group TSH levels stayed constant as did T4. None of the patients developed thyroid microsomal or thyroglobulin auto-antibodies and/or hyperthyroidism during the treatment.

CONCLUSIONS

Levothyroxine as well as iodine was effective in reducing thyroid size as well as thyroid growth stimulating immunoglobulins levels in endemic goitre patients. Since in both groups TSH levels were not related to thyroid size reduction, other factors than TSH suppression must be responsible for the observed thyroid size reduction. Iodine itself by virtue of its antiproliferative action on thyrocytes may have had a direct action on the goitre reduction during iodine treatment; however, the levothyroxine dose, containing less iodine, had a similar effect. A complicated picture hence emerges with regard to factors involved in the shrinkage of iodine deficiency goitre during thyroxine or iodine therapy. These findings indicate that TSH and thyroid growth promoting immunoglobulins are not the only influences on the size of endemic goitres, although it cannot be excluded that these two factors contribute to influence the pathogenetic process.

Identification of a thyroxine-containing self-epitope of thyroglobulin which triggers thyroid autoreactive T cells

Although thyroglobulin (Tg), the thyroid prohormone, is well known as a T cell dependent autoantigen in human and experimental autoimmune thyroid disease, very little is known about the molecular basis of Tg recognition by T cells. In this paper, we have characterized the epitopes recognized by two clonotypically distinct, murine Tg autoreactive T cell hybridomas, CH9 and ADA2. In vitro iodination of a Tg preparation which was deficient in in vivo organified iodine was first used to confirm our previous observation that these T cells recognize iodination-related epitopes in the Tg molecule. Affinity chromatography of tryptic peptides derived from normally iodinated human Tg revealed that these epitopes were exclusively located in thyroxine (T4) containing peptides. Through the use of synthetic T4-containing peptides, representing the four major hormonogenic sites in Tg, we demonstrated that both CH9 and ADA2 recognize an epitope containing the T4 at position 2553 in human Tg. Sets of overlapping 5mer to 12mer peptides around this T4 showed that the most potent peptide was a 9mer beginning at Asp 2551. The T4 was shown to be a critical residue, since its replacement with any of the 20 naturally occurring amino acids produced only nonstimulatory peptides. Since the T cell hybridomas could also be stimulated by major histocompatibility complex class II positive (interferon-gamma-treated) thyroid epithelial cells in vitro, and their parent T cell lines can induce thyroiditis on adoptive transfer, the T4-containing Tg sequence described here is implicated as a pathogenic epitope in murine thyroid autoimmunity.

Intrathyroidal lymphocytes from non toxic multinodular goiter: no evidence for production of thyroid stimulating antibodies

Although an autoimmune pathogenesis for non toxic goiter has been suggested, reports concerning circulating antibodies to TSH receptor structures have been conflicting. Intra thyroid lymphocytes, capable of secreting IgG, have been shown to be involved in the pathogenesis of Graves' and Hashimoto's diseases; therefore, the ability of conditioned media obtained from intra thyroid lymphocyte culture, and of IgG purified from these media, to stimulate cAMP accumulation and [3H]-Thymidine (TdR) uptake in FRTL-5 cells was investigated. The activity of IgG produced "in vitro" was compared with that of circulating IgG. Thyroid tissue samples were obtained at surgery from 21 patients with non toxic multinodular goiter (MNG), 5 patients with active Graves' disease (GD), and from 10 normal subjects, undergoing neck surgery for non-thyroidal pathology. IgG purified from media of GD lymphocyte cultures stimulated both cAMP accumulation and [3H]-TdR in 5 out of 5 cases: all of the IgG purified from control or MNG lymphocyte culture media was not active in either assay. Circulating IgG did not affect cAMP accumulation or [3H]-TdR in any of the non toxic MNG cases: controls showed no changed at all. However, both activities represented were increased by GD IgG. Conditioned media from intra thyroid lymphocyte cultures significantly inhibited basal cAMP accumulation in 7 out of the 21 non toxic MNG samples and totally abolished the response in all GD patients. [3H]-TdR was not affected by IgG of any of the controls, but it had an inhibitory effect on 8 out of 21 non toxic MNG patients, and significantly stimulated [3H]-TdR in all GD patients. In conclusion, present data demonstrate that intra thyroid lymphocytes from non toxic MNG do not produce antibodies capable of mimicking TSH actions through the adenylate cyclase cascade. Conversely, soluble factors interacting in TSH-mediated functions of FRTL-5 cells are present in conditioned media of intra thyroid lymphocytes of GD and MNG thyroid lymphocytes of GD and MNG thyroid cultures.

Thyroid growth stimulating activity in highly purified IgG-fractions of patients with nonimmune thyroid diseases

Two different proliferation assays have been used to measure the proliferative potential of IgG-fractions from 57 patients with nontoxic goiter of an iodine-deficient area: primary human thyroid epithelial cells (TEC) and the thouroughly investigated FRTL-5 cell line. IgG-fractions from patients with nontoxic goiter (n = 30), nontoxic recurrent goiter (n = 8), toxic-nodular goiter (n = 15) and carcinoma of the thyroid (n = 4) were highly purified on DEAE-Sepharose and additionally Protein A-Sepharose in some cases. The two proliferation assays gave contradictory results: primary cultures of human thyroid epithelial cells (TEC) could not be stimulated by any of the patient's IgG-fractions nor by bTSH. The FRTL-5 cells, however, were stimulated with 10 microU/ml bTSH by 326% +/- 96% (range: 222% - 497%, p less than 0.001). In one experimental series, 72% of all patients exceeded mean + 2 SD of normal controls, when the stimulation index was referred to the effect of bTSH (NTG: 77%, Rec. G.: 88%, Tox. G.: 53%, Ca. thyroid: 75%). With a different method of calculation - stimulation index referred to the basal value - the number of patients above mean + 2 SD of normal controls decreased to 30% (NTG: 33%, Rec. G.: 12.5%, Tox. G.: 33%, Ca. thyroid: 25%). Statistical analysis, however, of results of different patient groups compared to the normal control group failed to show any significance.

The long-term outcome of thyroidectomy for sporadic non-toxic goitre

To study the long-term outcome after thyroidectomy, 113 sporadic non-toxic goitre patients who underwent thyroidectomy in our hospital in the period 1974-1983, were studied. Five patients complained of recurrent goitre; a goitre was found on inspection and palpation in these five and in 15 others. There were no differences between the 20 patients with goitre and the 93 patients without goitre with regard to sex, age, duration of goitre, indication and type of thyroidectomy, postoperative thyroid hormone medication, period of follow-up, and T4, T3, or TSH plasma values at the time of follow-up examination. Twenty-three patients complained of voice changes since thyroidectomy. In a case control study, included in this follow-up study, 19 patients with goitre, i.e. thyroid size I and II as estimated by inspection and palpation (cases), and 16 patients without goitre, i.e. thyroid size OA and OB (controls), were studied in more detail. No difference between cases and controls was found in any of the above mentioned parameters that could explain the recurrence of goitre. Thyroid volume (median) was greater in the cases (34.1 ml, range 7.9-83.4) than in the controls (10.3 ml, range 2.5-48.7) (P less than 0.001), although a considerable overlap between the two groups was observed. One or more thyroid nodules were found in 89.5% of the cases and in 62.5% of the controls (NS). Serum thyroid growth stimulating immunoglobulin (TGI) was present both in cases (68%) and controls (50%). TGI was present in high titres in all five patients who complained about recurrent goitre.(ABSTRACT TRUNCATED AT 250 WORDS)

Thyroid autoantigens and their relevance in the pathogenesis of thyroid autoimmunity

Humoral and cellular immune responses are both involved in autoimmune disorders of the thyroid gland. In the last five years, new substantial data have been obtained on the nature and the expression of thyroid cell surface autoantigens and on the demonstration of the functional heterogeneity of autoantibodies to the thyroid stimulating hormone (TSH) receptor. In the present report, attention will be mainly focused on recent studies carried out in our laboratory. The main autoantigens so far identified include the 'microsomal' antigen, thyroglobulin and the TSH receptor. For many years the 'microsomal' antigen (M) was considered a poorly characterized constituent of the cytoplasm of the thyroid cell. In the last five years, several lines of evidence were provided indicating that M is also well represented on the surface of the follicular cell and is identical to thyroid peroxidase (TPO). The use of anti-TPO monoclonal antibodies, presently available, have confirmed this antigenic identity. Microsomal (anti-TPO) antibodies are very useful markers of autoimmune thyroid disorders and are generally present in Hashimoto's thyroiditis, idiopathic myxedema and Graves' disease. TSH receptor antibodies (TRAb) are present in the sera of patients with Graves' disease. TRAb are able to stimulate thyroid adenylate cyclase and also to mimic TSH in its thyroid growth stimulation. Thus, these antibodies may have a pathogenetic role in goiter formation and in thyroid hyperfunction in Graves' disease. TRAb were also shown to inhibit both TSH binding to its receptor and TSH-stimulated adenylate cyclase activity. Recently TRAb, which inhibited TSH-stimulated adenylate cyclase activity, were found in idiopathic myxedema patients and may be responsible for impairment of thyroid function.(ABSTRACT TRUNCATED AT 250 WORDS)

Simultaneous assay of thyroid adenylate cyclase- and growth-stimulating antibodies using FRTL-5 cells. Evidence suggesting their identity in patients with Graves' disease

The relationship between thyroid growth-stimulating antibodies (TGSAb) and thyroid adenylate cyclase-stimulating antibodies (TSAb) in patients with Graves' disease is still a matter of controversy. To investigate this problem, we have developed an assay for the simultaneous measurement of TSAb and TGSAb using FRTL-5 cells. TSAb was detected by its ability to stimulate iodide (I-) uptake and TGSAb by the 3H-thymidine ([3H]-Tdr) incorporation assay. Thirty-four immunoglobulin G (IgG) preparations from patients with active Graves' disease were selected from a previous series in order to include both TSAb-negative IgGs (n = 9) and TSAb-positive IgGs (n = 25) by the cAMP stimulation assay, with a wide range of stimulatory activity. With one exception, the TSAb-positive IgGs produced a significant stimulation of I- uptake; 20 of them were also TGSAb-positive. The nine IgGs negative in the cAMP assay, were also negative in the I-uptake and the [3H]-Tdr incorporation assays. The majority of samples had a similar potency in the two assays and a significant positive correlation was found (r = 0.76; P less than 0.001). Two IgGs previously shown to inhibit TSH-stimulated adenylate cyclase in FRTL-5 cells produced an almost complete inhibition (80-90%) of both TSH- and Graves' IgG-stimulated I- uptake and [3H]-Tdr incorporation. In conclusion, using a simultaneous assay for thyroid growth and adenylate cyclase stimulation, TGSAb in Graves' patients were found only in TSAb-positive IgGs; both Graves' IgG-stimulated activities were inhibited by antibodies blocking the TSH-dependent adenylate cyclase stimulation. Our data strongly suggest that the same antibody may be responsible for both goitre and thyroid hyperfunction of Graves' disease.

An improved metaphase index assay for detecting thyroid growth stimulators using FRTL-5 thyroid cells cultured on a microtitre plate

The metaphase index assay (MIA) for thyroid growth stimulators, as originally described, used FRTL-5 thyroid cells cultured in Bellco culture chambers and glass microscope slides. The metaphases were observed using the nuclear strain aceto-lacto orcein. However the surface properties of the glass proved to be variable and so polystyrene microscope slides were substituted. The aceto-lacto orcein stain was found to be unsuitable for use with polystyrene because of the solvents and mountant used. Therefore combinations of various other nuclear stains and mounting media were tested. The Giemsa stain, which was found to be the most satisfactory, could be applied to FRTL-5 cells maintained on the large variety of plastic supports now available for tissue culture, e.g., 96 well microtitre plates. This permitted the design of an MIA which is much more convenient, robust and economical in its use of clinical samples. The results with seven IgG preparations derived from the sera of patients with a variety of thyroid disorders are presented. In its revised form, the metaphase index assay provides a rapid screening assay for thyroid growth stimulators, such as autoantibodies and TSH.

Autoimmune thyroid disease: immunological, pathological, and clinical aspects

Autoimmune thyroiditis, most notably Hashimoto's thyroiditis, appears to be increasing in prevalence and is now more easily detected by sensitive laboratory tests and more invasive procedures such as fine needle aspiration. During the last decade, marked progress has been made in the understanding of these diseases. There is a greater awareness of the interaction between the humoral and cell-mediated arms of the immune system in autoimmune thyroiditis. Recent studies implicate a subpopulation of suppressor T lymphocytes which have an antigen-specific defect, resulting in their suboptimal interaction with the helper T lymphocytes and subsequent autoimmune manifestations. There is some evidence that thyroid epithelial cells which inappropriately express HLA-DR may enhance presentation of thyroid antigens to the immune system, possibly significant in the initiation or enhancement of the autoimmune response. The presence of various antithyroid autoantibodies allows the use of laboratory assays to confirm the clinical diagnosis and predict the results of treatment. There appears to be predisposing genetic factors in the development of autoimmune thyroiditis, with some geographical and racial differences. Environmental factors, most notably dietary intake of iodine, have also been implicated in the pathogenesis of Hashimoto's thyroiditis. Several animal models have been developed addressing such issues. Ongoing studies in the areas of postpartum thyroiditis and childhood thyroiditis are helpful in clarifying their relationship with Hashimoto's thyroiditis. Graves' disease and postpartum thyroiditis are being investigated as possible causes of postpartum depression. The association of Hashimoto's thyroiditis and carcinoma of the thyroid gland is still controversial, but its relationship with malignant lymphoma is now well accepted. Thus, although the pathogenesis of autoimmune thyroiditis remains elusive, there has been significant refinement of the clinical diagnosis, and immunological abnormalities of specific intrathyroidal lymphocytes have been identified. Hopefully, these new areas of knowledge will assist in the treatment of these diseases and in the prevention of the development of malignant lymphomas of the thyroid gland.

Intrinsic abnormality of thyroid cells from a patient with a Brobdingnagian goiter

Thyrocytes from normal and goitrous portions of the thyroid gland from a patient with an enormous (635 gm) goiter were cultured in media, and their relative abilities to uptake thymidine, synthesize DNA, and secrete Tg and T4 were assessed. Tg, T4 and the ratio Tg/T4 in media at 72 h were 120 micrograms/dl, 1.6 micrograms/dl and 75 for normal cells, and 410 micrograms/dl and 273 for goitrous cells. DNA synthesis was 30-100% greater in goitrous than normal cells over a period of 72 h indicating abnormally high rates of cell division and growth, but their thymidine uptake was only 20% of that in normal cells. TSH elicited stimulation of thymidine uptake and DNA synthesis both in goitrous and in normal cells, but to a lesser extent in goitrous cells. No evidence of growth stimulating autoantibody activity was detected in the patient's serum. These data indicate that although the ability of goitrous cells to uptake thymidine was impaired, their DNA synthesis was more active than normal thyroid, which may have led to disordered cell growth as evidenced by the enormous goiter size in this patient. Although goitrous cells secreted more than three times as much Tg into media compared to normal, media T4 levels were similar, indicating an increased synthesis yet low iodination of Tg in goitrous cells. There does not appear to be any support for TGSI mediation of the goiter in this patient, but rather, the goiter may have been due to an intrinsic alteration in DNA synthesis resulting in vigorous cell growth.

The relationships between serum T3 index, thyroid volume, and thyroid stimulating, TSH receptor binding and thyroid growth stimulating antibodies in untreated Graves' disease

This study represents an international double-blind collaborative study of abnormal immunoglobulin activity in untreated Graves' disease. Laboratories in two countries participated in a comparison of thyrotrophin binding inhibiting (TBII), thyroid stimulating (TSAb), and growth stimulating (TGI) immunoglobulins with clinical data, including ultrasonically measured thyroid size. The correlation between TGI and thyroid volume (n = 25, Rs = 0.54, P less than 0.05) and the fact that 9 of 10 patients with high range TGI values had large goitres establish the relationship between TGI and goitre, confirming that the in-vitro activity of these antibodies is related to an in-vivo action. In addition, both TBII and TSAb correlated with serum free T3 indices (TBII: n = 60, Rs = 0.46, P less than 0.001, and TSAb: n = 60, Rs = 0.64, P less than 0.001). Moreover, both TBII and TSAb correlated with thyroid volume (TBII: n = 60, Rs = 0.37, P less than 0.01, and TSAb: n = 60, Rs = 0.41, P less than 0.01) suggesting that these antibodies are also important in development of goitre in Graves' disease. Finally, some correlation between the antibodies was observed. TBII correlated with TSAb (n = 60, Rs = 0.47, P less than 0.001), and in the 16 patients with positive TGI results, this activity correlated with TBII (Rs = 0.54, P less than 0.05), but not with TSAb. Also some cases were found with corresponding high range TBII and TGI, while negative for TSAb, suggesting a close relationship between the in-vitro measurement of TSH binding and TGI.

In vitro demonstration of a TSH-specific growth desensitising mechanism in rat thyroid epithelium

Sustained elevation of serum thyrotropin (TSH) induces an initial proliferation of rat thyroid follicular cells, leading to goitre formation followed by a 'plateau phase' in which the growth response to TSH is lost. To investigate this growth desensitisation mechanism, we have compared the sensitivity to growth factors of normal and 'plateau phase' rat thyroid epithelium in primary follicle cultures. Insulin at supraphysiological concentrations stimulates growth (DNA synthesis) in both cell types. TSH at a concentration found in 'plateau phase' animals (0.1 mU/ml) is maximally growth stimulatory for normal, but not significantly stimulatory for 'plateau' epithelium. At much higher concentrations however (greater than or equal to mU/ml) an equal response is obtained from both. We conclude that the growth desensitising mechanism is intrinsic to the follicular cell, is at least partly specific to TSH, and is effective only over the range of TSH concentrations found in vivo.

Detection of thyroid-stimulating antibodies in thyroid diseases, employing rat thyroid fragment perifusion

The technique of perifusing rat thyroid fragments was used to investigate the presence of thyroid-stimulating antibodies (TSAb) in the sera of 48 patients. Response to IgG was measured by determining the mean rate of release of T4 (R) during a 30-min perifusion and the secretion peak (Imax) by means of samples taken every 5 min. Values found to be above the mean + 2 SD of the control values of R or Imax were considered to be positive. TSAb were found in all the 17 patients with untreated Graves' disease (GD) and in the 2 treated with antithyroid drugs, but not in the 3 who had undergone surgery or 131I treatment or in the 2 on corticosteroid treatment. TSAb were also found in 2 out of 3 patients with untreated nodular toxic goiter (UNTG) and in 6 out of 8 with diffuse nontoxic goiter (DNG) but at lower levels. In the untreated GD group, R and Imax correlated significantly with the corresponding IgG concentrations (from 90 to 800 micrograms/ml), suggesting TSAb activity which can be compared from one patient to another. TSAb activity did not correlate with thyroid function tests in any group. In all the groups it induced an early secretion peak followed by a decreasing response throughout the stimulation period, as was previously found with 65 mIU/ml TSH. The specificity of this technique was verified by five different control methods: the perifusion technique was checked by using KRBG buffer alone; sera were studied from a group of healthy controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of goitrous autoimmune thyroiditis with HLA-DR3 in eastern Hungary

An association of HLA-DR5 and goitrous autoimmune thyroiditis has been reported elsewhere (Farid et al., 1981; Weissel et al., 1980). Recently, the disease was found to be associated with HLA-DR4 in Newfoundlanders (Farid & Thompson, 1986). In order to find out whether different HLA associations with the disease may be found in different ethnic groups, we have now typed 68 patients with autoimmune goitrous thyroiditis from Eastern Hungary for HLA-A, -B, -C, and -DR antigens; 66 of these patients were also typed for IgG heavy-chain markers (Gm). A significant increase in DR3 (OR = 3.30) and a non-significant increase in DR4 (OR = 1.67) were found in the patients when compared with controls. The Gm3 allele, g, interacted with DR3 to enhance the risk for goitrous autoimmune thyroiditis. Hashimoto's disease may show different associations in different ethnic groups, and indeed within the same ethnic group, when newly diagnosed patients are typed several years apart.

Does prophylactic thyroxine treatment after operation for non-toxic goitre influence thyroid size?

In order to evaluate the influence of thyroxine treatment on thyroid volume after thyroidectomy for non-toxic goitre 110 consecutive patients were randomised to receive thyroxine (150 micrograms daily) or no treatment three months after operation. Thyroid volume determined by ultrasonography did not differ significantly between the two groups one year after operation. Nevertheless, a similar decrease in volume was seen from three to 12 months postoperatively in the thyroxine treated and no treatment groups (median 18 (range 8-70) ml to 16 (range 7-57) ml, and median 20 (range 9-72) ml to 17 (range 8-58) ml, respectively). Three patients (two given thyroxine) had recurrence of goitre within the observation period of one year. In this series thyroid volume decreased during the first postoperative year independently of thyroxine treatment. Hence it seems questionable whether postoperative thyroid function studies can identify patients at risk of recurrence of goitre after operation for non-toxic goitre and whether routine postoperative treatment with thyroxine is justifiable.

Organ-specific autoimmunity: a 1986 overview

The normally functioning immune system is subject to intricate networks of regulatory mechanisms: it is therefore not surprising to find that autoimmune diseases present a complex pathogenic picture in which the relative contributions of various factors probably determine the precise nature and course of disease. This is particularly evident in the effector mechanisms of organ-specific autoimmunity which are described in this chapter. These ultimately give rise to the disease symptoms, and can be directly cytotoxic, or may either stimulate or block functional activity or growth of the target cells. Their various contributions to human diseases are becoming more firmly established, as in Type I diabetes, or are only now being described, as in the case of EC-Ab in protracted diarrhea of infancy and as evidenced by the growing lists of receptor-stimulating or -blocking antibodies. The nature and precise location of relevant autoantigens is also coming under closer scrutiny. The answers to the question of why these diseases arise in the first place remain more elusive. However, it is again likely that a variety of factors can contribute. The attractive possibility of a role for idiotypic interactions is gaining ground, particularly within the context of antibodies to hormones and their receptors. Another potential mechanism which we believe may be of central importance, particularly in the development of organ-specific destructive autoimmunity, and which we have discussed here in detail, is the aberrant expression of HLA Class II molecules by target cells. Whether this is actually an initiating factor is presently not known, but its potential for promoting pathogenesis both early and late in the process is clear. Furthermore, the complex nature of the regulation of epithelial Class II expression may help to explain the heterogeneity of features and course of disease in different patients with the same underlying pathology. All these advances in our basic understanding of the disease processes should ultimately lead to more effective and specific means of therapeutic intervention.

Further evaluation of an immunoprecipitation assay for TSH-receptor autoantibodies in Graves' disease

In ten patients with untreated Graves' disease, quantitative titers of TSH receptor antibodies, as measured by a recently developed immunoprecipitation assay (IPA), were correlated with results obtained in three other methods and with the severity of the hyperthyroidism, as assessed by thyroid function tests. Nine patients were positive in the IPA, six in the TBII (TSH-binding inhibitor immunoglobulins), six in the TSI (thyroid-stimulating immunoglobulins), and seven in the TGI (thyroid-growth stimulating immunoglobulins) assay. Three patients were positive in all four assays. No correlation was found between the IPA values and the results obtained in the TBII, TSI, or TGI assays. There was a modest correlation between the TBII and TSI assays (r = .74, P less than 0.02). There was a modest but significant correlation between the IPA titers of TSH receptor antibodies and serum T3 concentration, both before treatment (r = .63, P less than 0.05) and during treatment (n = 5; r = .84, P less than 0.05). No correlation between the severity of the hyperthyroidism and TBII, TSI, or TGI assays was observed. Finally, TGI did not correlate with goiter size as estimated by palpation. These results suggest that the IPA may be useful in monitoring the immunologic activity of TSH receptor antibodies in patients with Graves' disease. They suggest further that the IPA detects a number of different subpopulations of TSH receptor antibodies, including TSI, TBII, and perhaps TGI. This property may be particularly useful in screening for monoclonal TSH receptor antibodies.

Immunologic factors in thyroid disease

The role of immunologic reactions against orbital-specific and orbital-thyroid antigens in the pathogenesis of autoimmune thyroid disorders and Graves' ophthalmopathy is discussed. Possible mechanisms for the association of ophthalmopathy and autoimmune thyroid disorders is discussed in relation to the role of autoantibodies against eye muscle antigens.

The pathogenesis of Graves' disease

The abnormally increased thyroid activity that is characteristic of Graves' disease is caused by immunoglobulins which specifically interact with the thyroid cell and stimulate it. Increases and decreases in thyroid activity in Graves' disease can be clearly related to rise and fall of these immunoglobulin-mediated activities. The level of immunoglobulin stimulatory activity can be used for prediction of the likelihood of neonatal Graves' disease and of recurrence of disease after cessation of treatment with antithyroid drugs. Investigation of patients with Graves' disease and their families has led to identification of particular human leukocyte antigens and genetically linked markers on immunoglobulins which both appear to incur increased susceptibility to certain autoimmune diseases. Differences in immune function, when compared with control populations, have been found in patients with these genetically linked markers. Protection against autoimmune disease is maintained by purposeful inhibition of any self-directed activity within each function of the immune system and by the controlling interaction of other immune functions. No single deficiency of immune function can be selected as giving the major risk of autoimmune disease, but rather a sum of relative defects resulting in an increased risk. In some patients with Graves' disease the self-protection mechanisms regain sufficient control of the immune functions to reduce the activity of the autoimmune disease, and the patient may achieve clinical remission. Often, however, there is evidence that abnormal immune activity directed against thyroid tissue has persisted with liability to recurrence of the Graves' disease.

Influence of thyroid autoantibodies on thyroid cellular growth in vitro

Porcine thyroid follicle cells, cultured in suspension, were employed to investigate the effects of immunoglobulin preparations from patients with colloid goitre, Graves' disease or Hashimoto's thyroiditis on thyroid growth in vitro. Epidermal growth factor (EGF, 19 ng/ml) was used as a reference for maximum growth stimulation and produced a 9-fold increase in [3H]thymidine incorporation. Immunoglobulins (1000 micrograms/ml) were found to increase [3H]thymidine incorporation compared to control: from 10 normal individuals 32 +/- 4% (mean +/- SEM, % of EGF response), from 10 patients with colloid goitre 26 +/- 4% (not significantly different from normal), from 10 patients with Graves' disease 19 +/- 3% (P less than 0.05) and from 15 patients with Hashimoto's thyroiditis 11 +/- 2% (P less than 0.001). No patient immunoglobulin preparation showed activity greater than that of normal individuals. The lower growth stimulatory activity in Graves' disease and Hashimoto's thyroiditis remained after heat inactivation of serum and is thought to reflect surface binding of thyroid autoantibodies.

In vitro generation of NADPH as an index of thyroid stimulating immunoglobulins (TGI) in goitrous disease

A quantitative cytochemical assay for the measurement of total NADPH formation in guinea pig thyroid tissue following incubation with thyroid stimulators was validated and applied to the measurement of such stimulators in IgG concentrates prepared from human plasma. Pentose shunt enzyme activity was not uniformly distributed in thyroid tissue but this could be overcome and NADPH generation in such tissue used to assess accurately thyroid stimulators if a sufficient number of thyroid cells were measured. Specificity studies showed that antiserum to human IgG significantly diminished the NADPH generating capacity of IgG concentrates prepared in plasma from goitrous patients while antiserum to h-TSH had no such effect. The measurement of thyroid growth stimulating immunoglobulins (TGI) depended not only on the amount of NADPH generated but also on the IgG concentration at which maximum responses occurred. TGI present in goitrous Graves' disease were 10 times more potent than those present in euthyroid goitre, while such stimulators when present in toxic nodular goitre appeared to possess an intermediate potency. This finding, when taken together with the demonstration that TSH stimulation decreased intercellular differences in pentose shunt activity, provides experimental evidence for the hypothesis that an acute intense growth stimulus affecting all thyroid cells produces the diffuse hyperplasia characteristic of Graves' disease. In contrast, the weaker stimulus observed in nodular goitre may, over a period of time, result in the asymmetric hyperplasia commonly observed in this condition.