Does LATS cause hyperthyroidism in Graves' disease? (A review biased toward the affirmative)

Does smoking increase relapse rates in Graves' disease?

We wondered whether the relapse rate of Graves' hyperthyroidism was increased amongst patients who smoked. To this end, a retrospective analysis of clinical and laboratory data of consecutive patients with Graves' disease was carried out. All patients were treated with thionamide anti-thyroid drugs (ATD) for at least one year and remission was defined as continued and biochemical euthyroidism, at least 6 months after discontinuing ATD. The study comprised 221 subjects with Graves' disease from a hospital-based population over 9 years. We took the following variables into account when assessing contribution to disease relapse: Goiter, Thyroid Associated Ophthalmopathy (TAO), and Time to euthyroidism after starting ATD and interaction between smoking and sex. Smoking had a marginally significant (p=0.081) deleterious effect on the likelihood of remission after ATD treatment for Graves' disease. The effect of smoking was, however, highly significant in males and indeed the deleterious effect on remissions may be restricted to males (odds ratio, 11.1; 95% confidence interval, 1.25 to 98.5). The presence of goiter (odds ratio, 3.8; 95% confidence interval, 2.05 to 7.1) and TAO (odds ratio, 1.8; 95% confidence interval, 0.993 to 3.18) forecasted lower chances of achieving remission. The shorter the time a patient became euthyroid after starting ATD the more likely his disease was to remit. We conclude that cigarette smoking increases the likelihood of Graves' disease recurrence in males treated with anti-thyroid drugs. Thus, smoking appears to be an important risk factor in the pathogenesis and outcome of Graves' disease patients at least in subsets of patients.

Bioassay of thyroid-stimulating immunoglobulins using human thyroid cell cultures: optimization and clinical assessment

Primary monolayer cultures of human thyroid cells have been used to investigate the intracellular cyclic AMP response to thyroid-stimulating immunoglobulins (TSIg) prepared from the sera of patients with Graves' disease. In particular, attention was directed towards dose-response characteristics obtained under differing incubation conditions, and an optimized incubation procedure based upon conditions consistent with the maximal precision of TSIg measurement was developed. The magnitude of the cyclic AMP response to a tested TSIg preparation was shown to be greatest after the longest incubation period investigated, 16 h, for all doses of TSIg investigated. The greatest precision of TSIg measurement, as determined by the lowest relative error, was obtained at an immunoglobulin (Ig) dose of 1 mg/ml, and when incubated at this dose level for 16 h, all Ig-enriched fractions prepared from the sera of 28 newly-diagnosed patients with Graves' disease significantly (P less than 0.05) raised the intracellular cyclic AMP level of thyroid cell monolayers. After thionamide drug therapy, the incidence of TSIg detection declined to 42% (5 of 12 patients). TSIg bioactivity was also found in 9 of 14 (64%) patients with euthyroid exophthalmos and in 4 of 11 (36%) cases of non-toxic goitre. In contrast, Ig's prepared from the sera of normal euthyroid volunteers were devoid of TSIg bioactivity.

Graves' ophthalmopathy. A clinical and immunologic review

Graves' thyroid disease and the orbitopathy which often accompanies it have puzzled physicians and scientists for more than 150 years. Although certain histopathological features have been documented, it is not known what mechanisms are responsible for the systemic and/or ocular disorders. The ocular condition characteristic of Graves' disease may exist in the absence of clinical or biochemical evidence of thyroid dysfunction, and when the systemic and ocular condition exist together, they may follow completely different clinical courses. Because the relationship between the thyroid disorder and the orbitopathy is not established, the authors refer not to "thyroid ophthalmopathy," but to "Graves' ophthalmopathy." In this review, histopathological features of Graves' ophthalmopathy are reviewed. The differential diagnosis of the ophthalmopathy and approaches to its evaluation are discussed, notably the T-4 radioimmunoassay, T-3 resin uptake and TSH tests, as well as CT scanning and ultrasonography. The characteristics of Classes 0-6 ophthalmopathy are outlined and the management of cases in each class is considered. The possible immunological basis for Graves' ophthalmopathy is also reviewed.

The clinical immunology of Graves' ophthalmopathy

Graves' ophthalmopathy is frequently a diagnostic and therapeutic dilemma for practicing ophthalmologists. We have reviewed the clinical immunology of this disorder with regard to clinical manifestations, humoral immunity, and cellular immunity. Special emphasis with applicable clinical and laboratory data is given to the hypothesis that Graves' thyrotoxicosis and ophthalmopathy may be frequently associated diseases rather than disorders caused by a common pathogenetic mechanism. Dysthyroidism may be the substrate for the development of the ophthalmopathy, but the two disorders probably are caused by different immunopathogenetic mechanisms.

Long-acting thyroid stimulator (LATS) and long acting thyroid stimulator protector (LATS-P) in untreated thyrotoxicosis

The prevalence of serum LATS and LATS-P in untreated Graves' disease has been studied in eighty-three patients with thyroid overactivity; twelve (14%) were found to have significant levels of LATs and LATS-P whilst fifty-nine (72%) had significant levels of LATS-P alone. Twelve (14%) had neither activity. There was a very wide range in both activities. LATS was invariably found in association with a significantly greater concentration of LATS-P. There was no correlation between LATS-P and thyroid mass, as estimated from scintiscanning, thyroidal radioiodine uptake at 4 and 48 h, total serum T4 and total serum T3. Neither LATS nor LATS-P were detected in eleven patients with toxic multinodular goitre nor four with solitary toxic adenoma.

The prediction of relapse after drug treatment of Graves' disease by assay of long acting thyroid stimulator-protector (LATS-P)

In a study of fifty-two patients with Graves' disease followed for 1 year after stopping antithyroid drugs, a strong relationship has been found between serum LATS-P and relapse. In those with serum LATS-P activity on stopping therapy, twenty-one (88%) out of twenty-four relapsed. In those with no LATS-P activity on stopping antithyroid drugs only eight (29%) out of twenty-eight relapsed and in five LATS-P was detectable at relapse. The overall prevalence of positive assays for LATS-P at relapse (90%) was similar to that seen in untreated Graves' disease.

Thyrotrophin binding inhibiting immunoglobulins in Graves' disease before, during and after antithyroid therapy, and its relation to long-acting thyroid stimulator

Thyrotrophin binding inhibiting immunoglublins (TBII) were measured in twenty-five patients with unequivocal hyperthyroid Graves' disease with a radioreceptor assay for TSH before, during and the end of treatment with antihyroid drugs and triiodothyronine. To assess the outcome of this therapy patients were followed for 10--90 months (mean 63 months). Before treatment there was significant correlation between TBII activity and serum thyroxine (r = -0.48, P less 0.05) and between TBII activated and 24 hour 131I thyroid uptake (r = -0.57, P less than 0.01). No relationship was found between TBII activated and 20 min, 4 hour and 48 hour 131I thyroid uptakes before institution of therapy. During treatment a significant correlation between TBII index and 20 min 131I thyroid uptake was found (r = -0.55, P less than 0.001). Both before and during treatment there was a significant correlation between TBII and LATS activity (r = -0.65, P less than 0.001). From the magnitude of this correlation coefficient it can be concluded that related, although not the same immunoglobulins, are measured with the two assay techniques. It is not possible to predict the occurrence of a relapse from the presence or absence of TBII activity at the end of treatment in this group of patients. The relapse rate was four out of eight for patients without TBII activity in their serum at the end of treatment and five out of nine for patients with TBII activity. From the data presented it can be concluded that although there is a significant relation between TBII activity and some indices of thyroid function before and during treatment, the correlation coefficients are too small to conclude that TBII alone is responsible for the hyperfunction of the thyroid. The same conclusion can be drawn from the fact that TBII activity has no prognostic value in relation to a possible relapse.

Effects of autoantibodies to the insulin receptor on isolated adipocytes. Studies of insulin binding and insulin action

Autoantibodies to the insulin receptor have been detected in the sera of several patients with the Type B syndrome of insulin resistance and acanthosis nigricans. In this study we have used three of these sera (B-1, B-2, and B-3) as probes of the insulin receptor in isolated rat adipocytes. Preincubation of adipocytes with each of the three sera resulted in an inhibition of subsequent [(125)I]insulin binding. 50% inhibition of binding occurred with serum dilutions of 1:5 to 1:7,500. As in our previous studies with other tissues, Scatchard analysis of the insulin-binding data was curvilinear consistent with negative cooperativity. Computer analysis suggested that in each case the inhibition of binding was due to a decrease in receptor affinity rather than a change in available receptor number. In addition to the effects on insulin binding, adipocytes pretreated with antireceptor sera also showed alterations in biological responses. All three sera produced some stimulation of basal glucose oxidation. With serum B-3, maximal stimulation of glucose oxidation occurred at a serum concentration that inhibited binding by only 10-15%, whereas with serum B-2 the dilution curves for inhibition of binding and stimulation of glucose oxidation were superimposable. Serum B-1 behaved as a partial agonist; that is, it inhibited binding more effectively than it stimulated glucose oxidation. Cells pretreated with this serum in a concentration which inhibited binding by 80% also showed a five-fold shift to the right in the dose response of insulin-stimulated glucose oxidation, whereas spermine-stimulated glucose oxidation was unaffected. Serum B-2, which contained the highest titer of antireceptor antibodies, also stimulated 2-deoxy-glucose transport, as well as glucose incorporation into lipid and glycogen. Both the ability of the serum to inhibit binding and stimulate glucose utilization were enriched in purified immunoglobulin fractions and retained in the F(ab')(2) fragment of the IgG. In addition, the bioactivity was blocked by antihuman IgG but not by anti-insulin antibodies. Enzymatic digestion of adipocytes with trypsin resulted in a complete loss of insulin-stimulated bioactivity of serum B-3, but had only minor effects on the glucose oxidation produced by serum B-1 or B-2.These data suggest that the antibodies present in these three sera bind to different determinants on the insulin receptor. Thus, these antibodies may be useful probes of receptor structure and function.

Thyrotoxicosis detected in a mass-screening program for neonatal hypothyroidism: demonstration of placental transfer of an immunoglobulin with marked lipolytic activity

A female infant born to a mother with active Graves disease and a strongly positive LATS developed neonatal thyrotoxicosis. The diagnosis was confirmed rapidly by the markedly elevated filter paper spot T4 (5.45 ng/40 microliter) taken on the fifth day of life as part of the Quebec Screening Program for Neonatal Hypothyroidism. Although the infant's serum was negative for LATS, it reacted strongly (as did the maternal serum) in the lipolytic assay for LATS. This case illustrates the ability of screening programs for neonatal hypothyroidism to detect cases of neonatal thyrotoxicosis and supports the hypothesis that this condition is secondary to the placental transfer of a thyroid-stimulating immunoglobulin.

Thyroid suppression tests during drug treatment of hyperthyroidism

In fifteen hyperthyroid patients treated for 5 or more consecutive years with propylthiouracil four or more yearly prognostic 'suppression' tests (Cassidy & VanderLaan, 1960) were done. In nine of the fifteen patients there was a progressive diminution over a period of 3-6 years in the values of these suppressed uptakes to 20% or below. Eight of these nine patients have remained euthyroid off therapy for 1-8 years (average 3-1 years). None have become hypothyroid. The data suggest a gradual continuing change in thyroid function over the course of years in some hyperthyroid patients on antithyroid therapy. This may be a long-term effect of the drug and may have prognostic significance.

[The problems surrounding subtotal struma resection in hyperthyroidism with endocrinous Ophthalmopathy (author's transl)]

Observation of 39 patients who had undergone surgery for hyperthyroidism with or without endocrine ophthalmopathy between 1965 and 1972 indicate that this type of therapy involves no higher risk than do medication of radiological measures as far as the course of ophthalmic changes is concerned. Examination of the basal and the TRH-stimulated TSH concentrations i.s. argues against any primarily pituitary cause for progressive ophthalmopathy after surgery. In addition, it elucidates the almost inevitable postoperative development of preclinical hypothyroidism while the clinical condition is still euthyroid, and indicates the necessity of constant postoperative hormone substitution.

Radioimmunoassay and the hormones of thyroid function

Radioimmunoassay (RIA) has provided the tools for wide-reaching investigations that have changed and continue to change many important concepts of thyroid physiology and pathosphysiology. The RIA vor human thyrotropin (TSH) was developed in 1965; development of the RIA for triiodothyronine (T3), thyroxine (T4), thyroxine-binding globulin (TBG), and, recently, thyrothropin-releasing hormone (TRH) and thyroglobulin (Tg) followed. The capacity to measure nanogram and picogram concentrations with relative ease and speed has permitted the demonstration of dynamic relationships of the intrathyroidal and circulating thyroid hormones to each other and to the pituitary and hypothalamic regulating hormones. Evidence for the presence of cross-influences between TRH and other hypothalamic regulating hormones on the secretion of pituitary hormones has accumulated. The impact of the new information on clinical practice is now becoming evident. There is new appreciation of the value of assaying serum T3 and TSH concentrations in the clinical management of patients with disturbed function of the thyroid, pituitary, or hypothalamus. The necessary components for RIA performance can be purchansed separately or in kit form from commercial sources. With appropriate quality-control procedures, precise, sensitive, and reliable data can be generated. Awareness of the specific technical problems relating to the RIA of these hormones is absolutely necessary to assure reliable results. The availability of kits or their components permits the performance of these studies in the community hospital and in reliable commercial-service laboratories.

Association of the long-acting thyroid stimulator protector with the immunoglobulin G fraction of serum from patients with thyrotoxicosis

Both the long-acting thyroid stimulator and the long-acting thyroid stimulator protector are associated with the immunoglobulin G fraction of human serum proteins. Fractionation of globulins by (NH4)2SO4 precipitation and DEAE-cellulose chromatography showed that the protector activity was associated with subfractions of differing electrophoretic mobility. Attempts to concentrate the protector in immunochemically pure immunoglobulin G prepared in this way may fail because of loss of protector activity with other immunoglobulin G fractions. Gel filtration on Sephadex G-150 indicated that protector activity was associated with 7-S proteins.

Neonatal hyperthyroidism and long-acting thyroid stimulator protector

Neonatal hyperthyroidism has been thought to result from transplacental passage of long-acting thyroid stimulator (L.A.T.S.) from a mother with Graves's disease. A case is presented here in which no L.A.T.S. was detected in the mother or neonate but another immunoglobulin, L.A.T.S. protector, a specific human thyroid stimulator, was shown to be present in the mother's serum. This stimulator may have been the cause of the neonatal hyperthyroidism.

Correlation between long-acting thyroid stimulator protector level and thyroid 131-I uptake in thyrotoxicosis

Out of 50 consecutive untreated patients with diffuse toxic goitre 15 showed long-acting thyroid stimulator (LATS), 30 showed LATS protector only, and five showed neither. LATS protector was present in all the patients with LATS. Infiltrative ophthalmopathy was less common in patients with LATS protector only (40%) than in patients with LATS also (67%), but the difference was not significant. There was a correlation between LATS protector level and thyroid (131)I uptake rate factor (k(1)), the coefficient (r) being 0.68 (P < 0.001). LATS level showed no such correlation. The results support the hypothesis that LATS protector is a pathogenic thyroid stimulator in patients with diffuse toxic goitre.

Effects of long-acting thyroid stimulator (LATS) and LATS protector on human thyroid adenyl cyclase activity

The long-acting thyroid stimulator (LATS) has been thought to be responsible for the hyperthyroidism of Graves's disease. It is detected by its effect on the mouse thyroid gland but cannot be found in all patients with hyperthyroidism. In an attempt to clarify the problem of LATS-negative hyperthyroidism, serum was obtained from untreated patients and its effect in vitro on human thyroid tissue examined, using the activation of adenyl cyclase as a measure of stimulation. Human thyroid adenyl cyclase was activated by both thyroid-stimulating hormone (TSH) and LATS. Thyroid tissue obtained from patients with Graves's disease was relatively less responsive to LATS than was non-toxic thyroid tissue. Of the 24 samples studied five contained LATS and all of these activated adenyl cyclase. The presence of LATS protector in LATS-negative hyperthyroid patients was confirmed but LATS-negative sera had no effect on human thyroid adenyl cyclase activity.