Optimization and clinical assessment of a radioreceptor assay for thyrotropin-binding inhibitor immunoglobulins

Seasonal variation in relapse rate of graves' disease after thionamide drug treatment

OBJECTIVE

Controversy abounds on the issue of seasonal variation in new onset of Graves' disease, partly due to the difficulty of precisely dating the exact start of symptoms. To address the possible relationship between climatic changes and disease activity from a different perspective, we reviewed time of relapse during regular follow-up after successful drug treatment with thionamides.

DESIGN

Retrospective analysis of a case series in a university clinic.

PATIENTS AND MEASUREMENTS

We consecutively registered patients who experienced re-emergence of hyperthyroidism between 1992 and 2001 after successful antithyroid drug therapy. Excluded were subjects with superimposing painless thyroiditis, in postpartum, on immunomodulatory drugs, or off thionamides prematurely on their own volition.

RESULTS

Fifty-two patients recurred 2 to 36 months after drug cessation. The frequency was higher in spring and summer (March to August) than in autumn and winter (September to February). With a new coated-tube radioreceptor assay, TSH binding inhibitor immunoglobulin activity was detected in sera from 87.5% of the reworsened patients.

CONCLUSIONS

Graves' disease tends to relapse more frequently in spring and summer. Further clinical studies are warranted to clarify underlying mechanism (s) for this seasonal variation.

Subclinical Graves' disease as a cause of subnormal TSH levels in euthyroid subjects

In order to elucidate causes of subclinical thyrotoxicosis, we reviewed records of thyroid function tests obtained in our hospital between 1990 and 1992 showing normal thyroid hormones and subnormal TSH levels, and analyzed underlying clinical conditions of the patients. Of 186 patients with normal T4 and/or free T4 and normal T3 and/or free T3 but subnormal TSH (< 0.1 mU/l) levels in serum, 150 were under treatment with antithyroid drugs for hyperthyroid Graves' disease or with thyroid hormones for hypothyroidism. Twelve were in remission after treatment for Graves' disease, and 4 had destructive thyroiditis. Of the remaining 20 patients, 4 had autonomously functioning thyroid nodule (AFTN), 9 had euthyroid ophthalmic Graves' disease (EOG), and 7 had diffuse goiter without apparent ophthalmopathy (DG). When thyroid stimulating antibodies (TSAb) were measured in the last 3 groups of the patients, they were detected in none with AFTN but in all patients with EOG and DG. These 7 DG patients without ophthalmopathy had a clinical feature showing unstable thyroid functions, changeable to euthyroidism, overt hyperthyroidism and even hypothyroidism during follow-up. In conclusion, TSAb measurement is useful for detection of subclinical Graves' disease in euthyroid subjects with subnormal TSH levels in serum.

Serial occurrence of two types of postpartum thyroid disorders. Usefulness of Tc-99m pertechnetate uptake

A 32-year-old woman with a history of Graves' disease had an episode of thyrotoxicosis 2.5 months after her first childbirth. Because of low thyroidal uptake of Tc-99m pertechnetate, a diagnosis of postpartum painless thyroiditis was made and the patient was observed without medication. After the normalization of serum levels of thyroid hormones, a second wave of thyrotoxic symptoms emerged. This time, the Tc-99m uptake was slightly elevated and the patient was diagnosed to have a relapse of Graves' disease. This case underscores the previously reported notion that thyroidal uptake was indispensable to distinguish these two causes of postpartum thyrotoxicosis.

A study of untreated Graves' patients with undetectable TSH binding inhibitor immunoglobulins and the effect of anti-thyroid drugs

OBJECTIVE

We previously reported the clinical characteristics of Graves' disease with undetectable TSH binding inhibitor immunoglobulins (TBII) at first visit, but a study of the prognosis of untreated TBII negative patients with anti-thyroid drug medication has never been undertaken. The aim of this paper is to study the difference between negative and positive TBII Graves' disease in relation to the effect of anti-thyroid drug treatment.

PATIENTS

From January 1986 to April 1991, 1545 patients with untreated Graves' disease were referred to Kuma Hospital, Kobe, Japan. Of these, 94 TRAb negative patients were identified. Another 83 TRAb positive patients were randomly selected from the other Graves' disease patients and served as a comparison group. Fifty-six of the 94 patients in the TBII negative group and 52 of the 83 patients in the TBII positive group completed treatment with methimazole only.

MEASUREMENTS

The trial was conducted as a retrospective study with a maximum treatment period of 36 months and a follow-up period of a further 12 months. From the original pool of patients, we classified 56 TBII negative patients into two groups according to the clinical course taken; Group A in whom TBII remained undetectable throughout methimazole treatment (9 men and 34 women, age 37.2 +/- 2.2 years), and Group B who became TBII positive (4 men and 9 women, 31.2 +/- 4.4 years). Fifty-two TBII positive patients served as the comparison Group C (8 men and 44 women, age 38.1 +/- 2.0 years).

RESULTS

Serum free T4 and free T3 levels in groups A and B were significantly lower before treatment than those of Group C (P < 0.001). The thyroid volumes of Group A and B patients were significantly smaller than those of Group C (P < 0.01). The level of TBII in Groups A and B was significantly lower than that in Group C (8.3 +/- 0.7 and 8.8 +/- 1.1 vs 57.0 +/- 2.8%, respectively, P < 0.001). The level of thyroid stimulating antibody (TSAb) in Groups A and B was significantly lower than that in Group C (478 +/- 71.0 and 761 +/- 140.3 vs 2143 +/- 280%, respectively, P < 0.01), and there were no significant differences in TSAb activities between Groups A and B. The remission rates in Groups A, B and C were 77.4, 36.4 and 36.5%, respectively. These data indicate that Group A has a good prognosis, but Group B has the same prognosis as Group C.

CONCLUSION

We conclude that patients in whom TSH binding inhibitor immunoglobulins remained negative have a much better prognosis than TSH binding inhibitor immunoglobulins positive patients or those who become TSH binding inhibitor immunoglobulins positive, having been initially negative.

Scintigraphic findings of the thyroid in hypothyroid patients with blocking-type TSH-receptor antibodies

The present study was designed to analyse the scintigraphic appearance of the thyroid in hypothyroid patients with blocking-type TSH receptor antibodies (TRAbs). Eleven hypothyroid patients with autoimmune thyroiditis positive for TSH binding inhibitor immunoglobulins (TBII) [80% +/- 12 (SD)%; normal < 11%] and for thyroid stimulation-blocking antibodies (TSBAbs) (90% +/- 9%: normal < 32%) were studied. Thyroid scanning was performed using technetium-99m or iodine-123, when the patients were hypothyroid. Analysis of the scan images revealed the presence of localized functioning areas in six patients (group 1), and no visualization of the thyroid in the remaining five patients (group 2). Patients in group 1 showed significantly higher uptake of 99mTc than those in group 2 (P < 0.05). Interestingly, three patients in group 1 were positive for thyroid-stimulating antibodies (TSAbs) (249% +/- 17%; normal < 145%), which were not detected in the remaining eight patients. Antibodies against thyroglobulin and microsomal antigens were detected in nine nine (81.8%) and 11 (100%) patients, respectively, but neither of these titres correlated with the scan image. Three patients in group 1 underwent scintigraphy again after treatment with thyroxine, at which time the functioning lesion was not noted. Fourteen hypothyroid patients with negative TBII displayed no such scintigraphic findings. Chronic stimulation of the thyroid by TSAbs and/or TSH might be responsible for the presence of the functioning lesion, but clarification of the mechanism requires further studies. In summary (1) TSAbs were detected in three (27.3%) of 11 hypothyroid patients with blocking TRAbs; (2) thyroid scintigraphy revealed the presence of localized functioning area(s) in approximately half of these cases.

Metastatic thyroid cancer presenting as thyrotoxicosis: report of three cases

Three patients with metastatic thyroid follicular carcinoma developed thyrotoxicosis. Two had mild T3 toxicosis without detectable TSH binding inhibitor immunoglobulins (TBII) or thyroid stimulating antibodies (TSAb). Considerable concentration of 131I by tumours occurred, although serum TSH was undetectable. The third patient developed thyrotoxicosis several months after treatment with 131I had commenced and this was associated with concurrent increase in both TBII (90%; normal, less than 11%) and TSAb (2100%). We conclude that thyrotoxicosis in patients with metastatic thyroid carcinoma may result from a large bulk of tumour functioning either autonomously or after stimulation by TSH receptor antibodies.

Immunological findings and thyroid function of untreated Graves' disease patients with undetectable TSH-binding inhibitor immunoglobulin

OBJECTIVE

TSH-binding inhibitory immunoglobulin (TBII) is undetectable in about 10% of untreated Graves' disease patients, but the clinical characteristics and immunological significance of this finding are unknown. In this study we evaluated the clinical characteristics of TBII negative Graves' disease.

PATIENTS

We examined TBII in 1048 untreated patients at Kuma hospital from 1986 to 1990 and found 69 TBII undetectable patients (12 men and 57 women, mean age +/- SEM 35 +/- 2 years, group A).

MEASUREMENTS

We compared the clinical characteristics and immunological findings of group A with 57 untreated TBII detectable Graves' patients who were selected randomly (11 men and 46 women, mean age +/- SEM 40 +/- 2 years, group B). T4, TSH, FT4, FT3, 123I thyroid uptake, TBII, thyroid stimulating antibodies (TSAb) and the volume of the thyroid using ultrasonography were measured at the first visit.

RESULTS

Serum T4, FT4 and FT3 levels in group A were significantly lower than those in group B (P < 0.001). The values of TSAb in group A were significantly lower than those in group B (593 +/- 67 (mean +/- SE) vs 2143 +/- 280%, respectively, P < 0.001). The 123I thyroid uptake in group A was significantly lower than that in group B (53.1 +/- 1.1 vs 61.4 +/- 1.4%, respectively, P < 0.01). The thyroid volume in group A was significantly smaller than that in group B (39.1 +/- 3.0 vs 51.3 +/- 3.3 ml, respectively, P < 0.01). TSAb was undetectable in about 10% (6) of the TBII negative untreated Graves' patients at their first visit.

CONCLUSION

In the present study, untreated TBII negative patients with Graves' disease were characterized by mild elevation of thyroid hormones, mildly elevated 123I uptake, weak TSAb activities and small goitres. The finding of both TBII and TSAb negative titres in untreated Graves' disease patients was also confirmed.

Stimulated iodide uptake in FRTL-5 cells preincubated with Graves' immunoglobulins in NaCl-free medium: a sensitive assay for thyroid-stimulating antibodies

The present study was designed to increase the sensitivity of iodide uptake assay for detecting thyroid-stimulating antibodies (TSAb). Based on the previous observations that TSAb are more active to increase cAMP levels in the NaCl-free condition, we improved the assay procedure and defined the optimum conditions: FRTL-5 cells were incubated with immunoglobulin (IgG) in NaCl-free medium for 3 days, and then 125I uptake in the cells was determined after 60 min. The sensitivity of iodide uptake assay for TSAb increased 3-fold by the modification, when assessed by the IgG concentration required to elicit the same response. The described assay is as sensitive as that using cAMP measurement in NaCl-free buffer. Thus, it could detect TSAb in all 21 patients with active Graves' disease and in 7 of 8 with ophthalmic Graves' disease but not in 29 of 30 control subjects. Thyroid stimulating activities assessed by these two assays correlated with each other (n = 29, r = 0.707, p < 0.001). False positive results obtained in 4 hypothyroid patients with Hashimoto's thyroiditis (serum TSH concentrations, 11-171 mU/L) could be prevented using anti-TSH antibodies. In summary, the described assay allows evaluation of stimulated thyroid function directly without affecting the detection of TSAb.

Two cases of Graves' disease with presentation of unilateral diffuse uptake of radioisotopes

We present two cases of Graves' disease whose initial thyroidal scintiscan with 99mTcO4- (Case 1) and 123I (Case 2) showed unilateral diffuse uptake of radioisotopes. Initial diagnosis was possibility of malignancy in Case 1 and Graves' disease or Plummer's disease in Case 2. Both cases underwent right hemithyroidectomy. Histopathology of the resected thyroid gland in both showed hyperplastic columnar epithelium and infiltrative lymphocytes which was compatible with Graves' disease. Twenty seven (Case 1) and eight months (Case 2) after operation, both presented with thyrotoxic symptoms associated with enlarged left lobe, increased serum free thyroid hormone concentrations, suppressed TSH concentration, increased thyroidal 123I uptake in the remaining left lobe, and positive thyrotropin receptor antibodies. Both cases were successfully treated with methimazole. It was concluded that initial radioisotope uptake as well as scintigram in rare subgroup of patients with Graves' disease could be similar with that of non-autoimmune autonomous goiter (Plummer's disease).

Increased uptake of iodine-131 in metastases of differentiated thyroid carcinoma associated with less severe hypothyroidism following total thyroidectomy

BACKGROUND

In an attempt to determine possible factors affecting the efficacy of iodine-131 (I-131) treatment for metastatic thyroid carcinoma, the authors focused their efforts on thyroid functions after total thyroidectomy.

METHODS

Between 1980 and 1991, 47 patients with lung metastases of differentiated thyroid carcinoma were treated with I-131. Relationships of the images on post-therapy scans with various clinical features were studied.

RESULTS

Among them, 28 (59.6%) showed I-131 uptake in the metastases on post-therapy scans. Younger patients had lesions that concentrated more radioactive iodine than did those of older patients. The amount of I-131 concentrated in the metastatic lesions correlated with serum triiodothyronine (T3), thyroxine (T4), and thyroglobulin levels and inversely with serum thyroid-stimulating hormone (TSH) levels determined at the time of therapy. Serum T3 and T4 levels were significantly higher in 28 patients with positive scans than in 19 patients with negative scans. Most patients who had metastases with markedly increased radioactivity were euthyroid or mildly hypothyroid, suggesting that thyroid hormones produced by tumor masses compensated for severe hypothyroidism after total thyroidectomy, and showed favorable responses to the treatment. In three patients successfully treated, decreases in serum thyroglobulin levels and the size of metastatic lesions were accompanied by the development of severe hypothyroidism.

CONCLUSIONS

The presence of a large amount of metastatic functioning thyroid tissues responsive to I-131 treatment can be suspected in patients with less severe hypothyroidism after total thyroidectomy.

Heterogeneity of thyrotropin binding inhibitor immunoglobulins in serum from untreated patients with hyperthyroid Graves' disease

We have previously established an assay for the simultaneous assessment of thyrotropin (TSH) binding inhibitor immunoglobulin (TBII) and thyroid stimulating autoantibody activities in cultured rat thyroid cells (FRTL-5 cell), and found a discrepancy in some patients with untreated Graves' disease between the activities of TBII measured in FRTL-5 cells (TBII-rc) and in solubilized thyroid membranes (TBII-pm). In three selected patients with untreated Graves' disease, the different dose-response relationship between TBII-rc and TBII-pm clearly indicated the heterogeneous populations of TBII-pm in patients' sera, with different binding affinities for TSH receptor in intact cells.

Induction of c-fos and c-myc mRNA expression by immunoglobulin G from patients with Graves' disease in thyrotrophin-dependent rat thyroid cell line (FRTL5)

The present study was conducted to evaluate effects of autoantibodies in patients with Graves' disease on induction of c-fos and c-myc mRNA expression in rat thyroid cell line (FRTL5). IgG fractions were isolated from 11 patients with Graves' disease, and six healthy subjects, with protein A-Sepharose. FRTL5 cells which had been grown to subconfluency and deprived of TSH for a week were exposed to the IgG for an hour. Expression of c-fos and c-myc mRNAs was examined by the Northern blot method using nick-translated v-fos and c-myc probes. C-fos and c-myc transcripts were induced by IgGs from two patients with Graves' disease, which displayed much higher activities in assays for TSH binding inhibitor immunoglobulins, thyroid stimulating antibodies and thyroid growth-stimulating immunoglobulins, assessed by measuring inhibition of 125I-TSH binding to the TSH-receptor, cAMP production and 3H-thymidine incorporation in FRTL5 cells, respectively, compared with those in the remaining patients. The induction of c-fos and c-myc mRNAs by IgG from a patient with Graves' disease was suppressed by preincubation with IgGs from two patients with primary myxoedema who were known to have a blocking type TSH-receptor antibody. These data suggest that the binding of the antibodies to the TSH-receptor followed by cAMP production is related to the induction of c-fos and c-myc mRNAs and, thus, to the growth of FRTL5 cells. To our knowledge, this is the first report demonstrating that autoantibodies induce proto-oncogene mRNA expression.

Follow-up study of thyroid stimulating-blocking antibodies in hypothyroid patients

It has been shown that hypothyroidism of some patients may be associated with increased activity of thyroid stimulating-blocking antibodies (TSBAb). The present study was undertaken to follow the course of thyroid blocking, stimulating immunoglobulins and TSH-binding inhibitor immunoglobulins (TBII) in six hypothyroid patients who had elevated TSBAb and were treated with T4. Four of the six had Graves' disease previously treated with antithyroidal drugs, one had Graves' disease treated with 131I and one had subacute thyroiditis and subsequently became hypothyroid. The patients were followed for 1-5 years. Blocking activity and TBII normalized in four of the six during T4 therapy, so T4 was discontinued and they remained euthyroid. These data indicate that it is important to monitor carefully thyroid function in hypothyroid patients treated with a fixed amount of T4 to avoid subclinical hyperthyroidism and its consequence, e.g. osteoporosis.

Presence of both stimulating and blocking types of TSH-receptor antibodies in sera from three patients with primary hypothyroidism

A case report of three patients with primary hypothyroidism who had potent TSH-binding inhibitor immunoglobulins (TBII) and both thyroid stimulating (TSAb) and thyroid stimulation-blocking antibodies (TSBAb) has been described. Two patients displayed symptoms and signs indistinguishable from those in primary myxoedema (cases 1 and 2), and another patient had a history of Graves' disease (case 3). TBII, TSAb and TSBAb activities were 90.0, 1084.2 and 94.5% in case 1, 91.5, 826.6 and 95.8% in case 2, 76.0, 230.0 and 95.0% in case 3, respectively (normal range, less than 11.0%, less than 145.0 and less than 22.0%, respectively. The results indicate that both stimulating and blocking types of TSH-receptor antibodies exist in these patients. The possible mechanism whereby hypothyroidism developed has been discussed.

Studies on thyrotrophin receptor antibodies in patients with euthyroid Graves' disease

Thyroid stimulating antibodies (TSAb) and TSH-binding inhibitor immunoglobulins (TBII) were assessed in 30 patients with euthyroid Graves' disease. TSAb were detected in 24 cases (80.0%), the incidence being not significantly different from that in hyperthyroid Graves' disease (29/30, 97.6%). On the other hand, the incidence of TBII in patients with euthyroid Graves' disease (12/30, 40.0%) was significantly lower than that in patients with hyperthyroid Graves' disease (30/30, 100.0%). The mean TSAb and TBII activities in the euthyroid patients were significantly lower than in the hyperthyroid patients (P less than 0.005 and P less than 0.001, respectively). Both TBII and, more closely, TSAb activities correlated with T3-nonsuppressibility and inhibition of serum TSH response to TRH stimulation. The findings supported the stimulation in vivo of the thyroid by these antibodies. Both antithyroglobulin and antimicrosomal antibody titres in euthyroid Graves' disease were significantly lower than in hyperthyroid Graves' disease (P less than 0.05, P less than 0.01, respectively). Goitre size was significantly smaller (P less than 0.001), and 99mTc thyroid uptake was significantly lower (P less than 0.001) in the euthyroid than in the hyperthyroid group. Thus, the reduced mass of thyroid tissues responding to the stimulators was considered to be one of the factors responsible for the euthyroidism despite the presence of TSAb. The high incidence of TSAb and relatively low incidence of TBII in euthyroid Graves' disease indicate that the presence of TSAb does not necessarily lead to hyperthyroidism and that the development of overt thyrotoxicosis may require augmentation of both TSAb and TBII.

Changes in thyroid-stimulating and TSH-binding inhibitory activities in a patient who developed hyperthyroidism due to Graves' disease following primary hypothyroidism

A 23-year-old female who developed thyrotoxic Graves' disease following primary hypothyroidism was reported. She presented with symptoms of hypothyroidism and slight exophthalmos. After primary hypothyroidism was confirmed, she was treated with T4 in a dose of 50 micrograms/d. Two months after delivery, 1 year after the initial diagnosis of hypothyroidism, hyperthyroidism developed while she was taking T4. Graves' disease was confirmed by persistent thyrotoxicosis, high 99mTc thyroidal uptake, negative T3 suppressibility and detection of TSH-receptor antibodies. During the hypothyroid phase, TSH-binding inhibitory immunoglobulins (TBII) could not be detected, while thyroid stimulating antibodies (TSAb) were positive showing between 5.8 and 9.0 fold increases in the amount of cAMP produced in cultured porcine thyroid cells. Her IgG did not inhibit TSH-induced cAMP increase in vitro. When she developed hyperthyroidism, TSAb activity became more potent (31.7 fold increase in cAMP) and TBII became positive (+61.3%).