Histometry of lymphoid infiltrate in the thyroid of primary thyrotoxicosis patients

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1 J. /in. Path., 1976, 29, 398*402 Histometry of lymphoid infiltrate in the thyroid of primary thyrotoxiosis patients Relation of extent of thyroiditis to preoperative drug treatment and postoperative hypothyroidism R. J. YOUNG, M. B. SHERWOOD1, J. G. SIMPSON, A. G. NICOL, W. MICHIE, AND J. SWANSON BECK From the Departments of Pathology, Universities of Duindee and Aberdeeni, Aberdeen Royal Infirmary and Department of Anatomy, University of St. Andrews SYNOPSIS The thyroids of primary thyrotoxiosis patients prepared for partial thyroidetomy with propranolol ontained muh more lymphoid infiltrate than those prepared with arbimazole. No relation was found between the extent of lymphoid infiltrate in the thyroid and the development of postoperative hypothyroidism either between or within the two drug treatment groups. This study has shown that the extent of thyroid infiltrate should not be used as the major fator in prediting hypothyroidism after subtotal thyroidetomy for primary thyrotoxiosis. Lymphoid infiltrate has long been reognized as a omponent of the thyroid gland in primary thyrotoxiosis (Wegelin, 1926), and it has been established that the preoperative titre of irulating antithyroid antibodies is related to the extent of lymphoid infiltration in the thyroid (Goudie et al, 1959; Buhanan et al, 1962; Irvine et al, 1962; Irvine and Stewart, 1967). It has been laimed that the inidene of postoperative hypothyroidism after subtotal thyroidetomy is higher in those patients whose thyroids show more extensive lymphoid infiltrate (Whitesell and Blak, 1949; Greene, 1950 and 1953; Levitt, 1951; Hargreaves and Garner, 1968). Sine these reports were based on semiquantitative measurement methods, we have re-investigated this problem using the more aurate histometri tehnique. This paper reports our findings on the relation of the extent of thyroiditis to the preoperative drug treatment regime and to the inidene of postoperative hypothyroidism. Material and Methods CLINICAL INVESTIGATIONS This study was undertaken on 95 female primary 'Present address: Medial Student, University of Manhester Correspondene: Professor J. Swanson Bek, Department of Pathology, Ninewells Hospital and Medial Shool, Dundee DD2 IUB Reeived for publiation 6 November 1975 thyrotoxiosis patients for whom subtotal thyroidetomy was regarded as the treatment of hoie. The diagnosis of primary thyrotoxiosis was based on the riteria of Young et a! (1975). Two groups of patients were studied: (a) Propranolol group Twenty-six thyroids were removed in the years from patients who were prepared for operation with propranolol. All patients had reeived the drug for at least six weeks up to and inluding the day of operation and none had reeived arbimazole or other antithyroid drug during the previous six months. (b) Carbimazole group Sixty-nine patients treated with arbimazole were studied. There were 17 thyroids from patients oming to operation during the period , and 52 thyroids from patients treated by operation during the period before the introdution of propranolol treatment in Aberdeen Royal Infirmary. The latter group of patients was seleted retrospetively so that they mathed the propranolol patients for deade of age and month of operation to avoid any bias that may have arisen in the assignment of patients to either of the preoperative drug treatment groups during the period All patients were euthyroid at the time of operation but there was onsiderable variation in the duration of pre- 398

2 Thyroiditis in thyrotoxiosis operative treatment with arbimazole: those patients referred diretly to the Thyroid Clini at Aberdeen Royal Infirmary by general pratitioners generally reeived a relatively short period of preoperative drug treatment (2-4 months), whereas those referred by other physiians generally had a more extended ourse of preoperative drug therapy (up to four years). All patients reeived potassium iodide for 10 days before operation. During this preoperative period, treatment with arbimazole was stopped whereas propranolol was ontinued through the operation. Postoperative hypothyroidism was assessed by the riteria used in our previous study (Young et al, 1975). PATHOLOGICAL METHODS Reseted thyroids were weighed and then the tissue was fixed in 4 % neutral buffered formaldehyde. After fixation the thyroids were ut into 5 mm slies; bloks were taken from any areas of unusual nakedeye appearane in addition to a minimum of two representative bloks from eah lobe. Setions (5,um) prepared from paraffin bloks were stained with haematoxylin and eosin with standard tehniques. Setions were examined with a 40 x objetive and a 10 x fousing eyepiee ontaining a 36-intersetion gratiule (Leitz ode number ). The volume proportion of the lymphoid tissue (% L) and of epithelium (% E) in the thyroid was measured with the point-ounting tehnique (Dunnill, 1968). In preliminary studies it was shown (1) that the standard error of the observations was less than 3 % when 20 fields were seleted for ounting using random numbers to define the o-ordinates of the Vernier sale of the mehanial stage, and (2) that examination of one setion with this method gave results losely omparable to those obtained from examination of several setions from the same gland. IMMUNOLOGICAL METHODS Antithyroglobulin antibody and antiytoplasmi antibody were estimated by the tanned red ell haemagglutination (Fulthorpe et al, 1961) and immunofluoresene (Bek, 1971) tehniques respetively. Results The amount of lymphoid tissue in the thyroids of the two groups is shown in the figure. There is onsiderable variation between patients in eah drug treatment group, but it is lear that the lymphoid infiltrate is more frequent and generally more abundant in thyroids from the propranolol group than in those from the arbimazole group (Wiloxon test ;Z., N 10 (. P (I Carbimazole Prepared Patients rotal No. 69) V'olume proportion lymphoid tissue (7L) Propranolol Prepared Patients (rotal No. = 26) 9-10 V'olume proportion lymphoid tissue OL) Figure Extent of lymphoid infiltrate in thyroids of primary thyrotoxiosis patients prepared for subtotal thyroidetomy with arbimazole or propranolol. 399 Tpropranolol = ; P < 00001). The findings in the reent and retrospetive groups of arbimazoletreated patients did not differ signifiantly. There was no qualitative differene either in the anatomial loalization, in the relative amounts of large and small aggregates of lymphoid ells, or in the inidene of germinal entres between the two drug treatment groups. Despite the marked differenes in extent of lymphoid tissue infiltrate between the thyroids of the two drug treatment groups, the inidene of positive tests for antithyroid antibodies was simnilar in the groups; antithyroglobulin antibody was positive in 23 % and 19% and antiytoplasmi antibody in 40% and 46% in the arbimazole and propranolol prepared patients respetively. The table shows that there is a signifiant relation between the extent of lymphoid infiltrate and the positive tests for antiytoplasmi antibody in both drug treatment groups. A signifiant relation between extent of lymphoid infiltrate and positive tests for antithyroglobulin antibody was established for the arbimazole group; only five out of 26 patients in the propranolol group had positive tests for antithyroglobulin and the lak of orrelation in this group is possibly a onsequene

3 400 Hypothesis that Observation A greater ifcondition B satisfied R. J. Yolng, M. B. Sherwood, J. G. Simpson, A. G. Niol, W. Mihie, and J. Swanson Bek Treatment Group Carbitnazole Propranolol (69 patients) (26 patients) CL Statistis p U Statistis Antiytoplasmi antibody positive 379 < <0025 %L Antithyroglobulin antibody positive 246 < NS %L Postoperative hypothyroidism 367 NS 63 0 NS %0o'E %%L > NS 49 0 NS Table Results of Mann- Whitney ranking tests on histometri measurements of volume proportions of lymphoid tissue in thyroids ofprimary thyrotoxiosis patients treated with iodide after a ourse of arbimazole or propranolol NS not signifiant at the 5 % level %L= volume proportion of lymphoid tissue in reseted thyroid,e volume proportion of epithelium tissue in reseted thyroid of the small number of patients studied and the lower inidene of the antithyroglobulin antibody. The inidene of postoperative hypothyroidism is similar in patients in the two drug treatment groups -19 out of 69 treated with arbimazole (28%) and eight out of 26 treated with propranolol (30 %). Moreover, the extent of lymphoid infiltrate was not related to the development of postoperative hypothyroidism in either of the drug treatment groups (table). Disussion In this study we have ompared the effets of two preoperative treatment regimes employing different drugs on the extent of lymphoid infiltrate in the thyroids of patients with primary thyrotoxiosis. Our findings must not be interpreted as a diret omparison of the iatrogeni effets of arbimazole and propranolol on the thyroid sine patients in the arbimazole group had been under treatment for longer periods than those who had reeived propranolol. Furthermore, propranolol treatment was ontinued through the operation, whereas arbimazole was stopped 10 days before operation, and both groups of patients reeived preoperative iodide. The amount of lymphoid tissue in the thyroid glands of the primary thyrotoxiosis patients treated with propranolol is substantially greater than in those treated with arbimazole, and an analogous differene has been seen in the extent of hyperplasia in the thymus of these patients (Simpson et al, 1975). Both findings may be related to the pharmaologial ation of these drugs. The onventional antithyroid drugs, suh as arbimazole, redue thyroid hormone synthesis and release and so make the patient euthyroid. By ontrast, propranolol is a potent speifi inhibitor of ardia and peripheral /- reeptors, whih redues tahyardia and peripheral vasodilatation but does not affet irulating thyroid hormone levels. Many animal experiments have shown that thyroxine an indue marked hyperplasia of the lymphoid tissues (Fisher, 1964). Consequently the most plausible explanation of our findings would be that the lymphoid tissues in arbimazole-treated patients have been released from exessive thyroid hormone stimulation and have partly reverted to normal by the time of operation, whereas the lymphoid tissues in the propranolol-treated patients ontinue to be subjeted to exessive thyroid hormone stimulation. Two other explanations for the findings should be onsidered. First, it is possible that the onventional antithyroid drugs have immunosuppressive properties in view of their hemial similarity to urail, but this pharmaologial ation has not been investigated; if this were so then it ould indue lymphoid tissue atrophy in the patients treated with arbimazole. Seondly, it is remotely possible that propranolol ould ause hyperplasia of lymphoid tissues by diret stimulation, but this explanation is unlikely sine the appearanes of the lymphoid tissues in propranolol-treated patients are similar to the historial pathologial desription of untreated primary thyrotoxiosis (Wegelin, 1926). The finding that lymphoid infiltrate is more abundant in patients with antithyroid antibodies onfirms and extends the work of Goudie et al (1959), Buhanan et al (1962), Irvine et al (1962), and Irvine and Stewart (1967). The nature of the lymphoid ells in thyroid infiltrate is not yet deided. In a preliminary report, Farid et al (1973) laim that T- lymphoytes are more numerous in the thyroids of patients with Graves' and Hashimoto's disease than in normal individuals, but the histopathologial observation that plasma ells are ommon in the areas of lymphoid infiltrate suggests that at least some of the lymphoytes must be B-ells. Shevah et al(l973), using a more disriminating tehnique, have shown that in Sjogren's syndrome, another putative 'autoimmune' disease, there are onsiderable num-

4 Thyroiditis in thyrotoxiosis bers of B-ells in the hroni inflammatory infiltrate. In the light of Volpe's hypothesis of a stimulatory role for lymphoytes in the pathogenesis of primary thyrotoxiosis (Volpe et al, 1974) it is of interest that no relation was established between the extent of thyroid epithelial hyperplasia (as measured by the volume proportion of epithelial ells in the thyroid) and that of lymphoid infiltration in either drug group (table). In this histometri study no relation was found between the extent of lymphoid infiltrate in the thyroid and postoperative hypothyroidism either between or within the two drug treatment groups. The inidene of hypothyrodism after partial thyroidetomy is similar for both treatment groups (28 % for arbimazole-prepared patients and 30 % for propranolol-prepared patients) even though the extent of lymphoid infiltrate was so muh more abundant in the propranolol group. These are surprising findings sine it is widely held that there is a high inidene of postoperative hypothyroidism in primary thyrotoxiosis patients who had an appreiable amount of lymphoid infiltrate in the reseted thyroid speimen. Three soures are ommonly ited. (a) Whitesell and Blak (1949) assessed the extent of thyroiditis as the mean of visual estimates of the extent of lymphoid infiltrate from 150 lowpower fields. They examined 86 thyroids with thyroiditis and all but five had greater than 10% of lymphoid infiltrate; the values for the majority lay in the range 10 %-40 % (these are muh greater than the values found in the present series). They found a strong orrelation between the degree of thyroiditis and postoperative hypothyroidism but the overall inidene of hypothyroidism in their series was only 29 %, similar to that of the present series. Furthermore, they noted that myxoedema failed to develop in some patients in spite of advaned thyroiditis and that myxoedema ourred not unommonly in patients with lesser degrees of thyroiditis. (b) Greene (1950) studied 161 thyrotoxiosis patients and reported that postoperative hypothyroidism ourred only when the lymphoid infiltrate ontained germinal entres. However, sine 88 % of these glands were desribed as nodular, it is diffiult to aept that his study was restrited to patients with primary thyrotoxiosis. () Levitt (1951) reviewed thyroid setions from 2114 patients who had ome to partial thyroidetomy; 1410 of these were onsidered to be thyrotoxi and the histologial appearanes were lassified into six ategories. It was shown that the inidene of postoperative hypothyroidism was markedly greater if the histologial appearane was that of diffuse lymphoid hyperplasia or fibrolymphoid hyperplasia, but his definition of these ategories appears to orrespond very losely with the urrently aepted appearane of Hashimoto's disease. No information was given in any of these reports on riteria for the diagnosis of either hyperor hypothyroidism, preoperative drug treatment, the findings at operation, the size of the thyroid remnant or the method of postoperative follow-up. Moreover, the methods used in these previous reports to estimate lymphoid tissue are at the best semiquantitative, as also was the reent study of van Welsum et al (1974), the only report whih disputes the relation between lymphoid infiltrate and postoperative hypothyroidism. It seems fair to onlude, therefore, that while the assoiation between the extent of lymphoid infiltrate and postoperative hypothyroidism has gained wide aeptane, the evidene for this has never been firmly based. The findings of the present study based on more aurate histometri methods suggest that the extent of thyroid lymphoid infiltrate is not by itself a major fator in antiipating hypothyroidism after subtotal thyroidetomy for primary thyrotoxiosis. This study was supported by a grant from the Sottish Hospital Endowments Researh Trust to JSB. Referenes 401 Bek, J. S. (1971). Immunofluoresene tehniques in immunopathology and histopathology. Assoiation of Clinial Pathologists' Broadsheet 69, London. Buhanan, W. W., Koutras, D. A., Crooks, J., Alexander, W. D., Brass, W., Anderson, J. R., Goudie, R. B., and Gray, K. G. (1962). The linial signifiane of the omplement-fixation test in thyrotoxiosis. J. Endor., 24, Dunnill, M. S. (1968). Quantitative methods in histology. 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