The influence of remnant size, antithyroid antibodies, thyroid morphology, and lymphocyte infiltration on thyroid function after subtotal resection for hyperthyroidism

Current approach to surgical management of hyperthyroidism

Hyperthyroidism is a set of disorders that involve excess synthesis and secretion of thyroid hormones by the thyroid gland, which leads to thyrotoxicosis. The most common forms of hyperthyroidism include diffuse toxic goiter (Graves' disease), toxic multinodular goiter (Plummer disease), and a solitary toxic adenoma. The most reliable screening measure of thyroid function is the thyroid-stimulating hormone (TSH) level. Options for treatment of hyperthyroidism include: antithyroid drugs, radioactive iodine therapy (the preferred treatment of hyperthyroidism among US thyroid specialists), or thyroidectomy. Massive thyroid enlargement with compressive symptoms, a suspicious nodule, Graves' orbitopathy, and patient preference are indications for surgical treatment of thyrotoxicosis. This paper reviews the current literature and controversies on the surgical approach to the management of hyperthyroidism.

Treatment of patients with Graves' disease and the appropriate extent of thyroidectomy

Graves' disease is an autoimmune disorder caused by thyroid stimulating auto-antibodies directed against the thyrotropin receptor on thyroid follicular cells. It is the most common cause of hyperthyroidism and is associated with cardiovascular, ophthalmologic and other systemic manifestations. Three treatment options are available for Graves' disease: anti-thyroid drugs, radioactive iodine and thyroidectomy. While thyroidectomy is the least common option used for treatment of Graves' disease, it is preferentially indicated for patients with a large goiter causing compressive symptoms, suspicious or malignant thyroid nodules or significant ophthalmopathy. The best operation for Graves' disease has been a matter of debate. The standard operation was a subtotal thyroidectomy for much of the twentieth century, however, over the past 20 years total thyroidectomy has been increasingly performed. Herein, we provide a historical perspective and review the current literature, including randomized controlled trials, systematic reviews and meta-analyses and conclude that total thyroidectomy is the preferred option for the surgical treatment of Graves' disease, with a nearly 0% recurrence rate, predictable postoperative hypothyroidism and a low complication rate comparable to subtotal thyroidectomy when performed by high-volume thyroid surgeons.

Reoperative thyroidectomy for benign thyroid disease

BACKGROUND

Subtotal thyroidectomy for benign thyroid disease (BTD) may lead to delayed recurrence, thus necessitating reoperative surgery. We describe our experience with reoperative thyroidectomy for BTD and recommendations for definitive primary management.

METHODS

Patients undergoing thyroid surgery between 2003 and 2007 by a single surgeon were prospectively assessed. Numerous clinical parameters were evaluated, including time interval between primary and reoperative surgery and complications.

RESULTS

In all, 321 thyroidectomies were identified: 45 were reoperative and 22 were related to BTD after primary surgery done elsewhere. Median interval between the primary and reoperative procedure was 8.5 years. No recurrences followed total thyroidectomy or total thyroid lobectomy. There were no cases of permanent or transient recurrent laryngeal nerve (RLN) injury related to reoperative surgery. There was 1 case of transient hypocalcemia.

CONCLUSIONS

Although reoperative thyroidectomy can be performed safely in the hands of experienced surgeons, a thorough initial surgical procedure should obviate the need for exposure to this additional risk.

Elevação de hormônio tireoestimulante (TSH) após as lobectomias: incidência e fatores associados

OBJETIVO: Determinar a freqüência de elevação da dosagem sérica do hormônio tireoestimulante (TSH) em pacientes submetidos à lobectomia da tireóide, em um período de até 12 semanas após a operação, buscando fatores associados à sua ocorrência. MÉTODO: Foram analisados retrospectivamente 88 pacientes submetidos à lobectomia da tireóide no Serviço de Cirurgia de Cabeça e Pescoço do Hospital das Clínicas da FMUSP, no período de setembro de 2002 a setembro de 2004. Realizaram-se dosagens de hormônios tireoideanos a partir de quatro semanas após a cirurgia. Excluíram-se os pacientes com dosagens hormonais pré-operatórias alteradas, os casos que necessitaram de totalização da tireoidectomia e também aqueles em que houve perda do seguimento pós-operatório. Foram analisados os dados quanto à idade e ao sexo dos pacientes, quanto à presença de tireoidite no estudo histopatológico da tireóide e quanto ao tempo de aparecimento do hipotireoidismo. A análise estatística dos dados obtidos foi realizada através do teste qui-quadrado de Pearson. RESULTADOS: Dos 88 pacientes, 71 (80,7%) eram mulheres. A idade média foi de 41,7 anos. Observou-se elevação do TSH em 20 (22,73%) dos 88 pacientes estudados. Não foi observada diferença estatisticamente significante na incidência de elevação do TSH, quando analisados quanto ao sexo, à idade ou à presença de tireoidite. CONCLUSÃO: A elevação do TSH é freqüente após lobectomias da tireóide e ocorre, muitas vezes, precocemente após a cirurgia. Não se encontraram, neste estudo, fatores que pudessem predizer sua ocorrência a curto prazo.

Subtotal Thyroidectomy for Benign Multinodular Goiter: A 6-Month Postoperative Study of the Remnant’s Function and Sonographic Aspect

BACKGROUND

The purpose was to evaluate the thyroid function after subtotal thyroidectomy.

METHODS

One hundred and nineteen patients operated on for multinodular benign goiter were included in this prospective study. Results of the surgical treatment were evaluated 6 months after operation by thyroid-stimulating hormone (TSH) assay and cervical echography.

RESULTS

Thyroid-stimulating hormone levels correlated inversely (r=-0.78) with the thyroid remnant volumes. Forty-seven patients presented with a hypoechoic aspect of the remnant. Isoechoic and hypoechoic remnant volumes were similar; however, 46 of the 47 patients with a hypoechoic remnant (97.9%) had TSH levels higher than 5 mU/l vs. 39 of the 72 patients (54.2%) with an isoechoic aspect. No predictive factor for the occurrence of this hypoechoic feature was found.

CONCLUSIONS

After sub-total thyroidectomy for benign multinodular goiter, the volume of the remnant is not the only determinant of the occurrence of postoperative hypothyroidism. The appearance of a hypoechoic aspect of the remnant is also a strong predictive factor for such an outcome. In this case the occurrence of hypothyroidism is quite constant whatever the volume of the thyroid remnant. Since this evolution toward a hypoechoic aspect of the remnant is unpredictable, our results are an additional argument in favor of total thyroidectomy for benign multinodular goiter.

The surgical management of Graves' disease

BACKGROUND

The historical aspects of the pathophysiology and treatment of Graves' disease are briefly discussed in this paper.

MATERIALS AND METHODS

The three treatment modalities of Graves' disease are anti-thyroid drug therapy, radioactive iodine therapy, and surgery. Although the majority of patients with Graves' disease in the U.S. are treated with radioactive iodine, surgery still plays an important role when patients cannot tolerate anti-thyroid drug therapy, when medical treatment is rejected by patients, or when surgery is deemed the fastest and safest route in managing the patient.

CONCLUSIONS

The indications for surgical management of Graves' disease are discussed with emphasis on available data supporting the extent of thyroid resection based on the incidences of hypothyroidism, recurrence of hyperthyroidism, recurrent laryngeal nerve injury and hypoparathyroidism.

Postoperative endocrine function in patients with surgically treated thyrotoxicosis

BACKGROUND

Endocrine function after surgery for thyrotoxicosis is difficult to predict. The operative morbidity and long-term thyroid function of patients surgically treated for thyrotoxicosis is presented, and factors postulated to affect long-term function are correlated with outcome.

METHODS

The clinical records of 289 consecutive patients who underwent surgery for thyrotoxicosis were reviewed. Indications for surgery, intraoperative findings, postoperative complications, and endocrine status 1, 2, and 5 years after surgery were analyzed. Sex, age, duration of medical treatment, weight of thyroid removed and preserved, and antimicrosomal/antithyroglobulin antibody status were correlated with outcome 5 years after surgery.

RESULTS

The incidence of permanent recurrent laryngeal nerve injury and hypocalcemia were 0.7% and 1.7%. The cumulative hypothyroid and hyperthyroid rates for the first, second, and fifth postoperative years were 13.8% and 3.5%, 14.5% and 4.8%, and 15.6% and 8.0%. All the prognostic variables analyzed did not achieve a significant correlation with outcome at 5 years by univariate and multivariate age- and sex-adjusted relative risk.

CONCLUSIONS

Failure from hypothyroidism develops early; recurrent hyperthyroidism increases with the number of years of follow-up. Patients undergoing subtotal thyroidectomy warrant long-term follow-up because of the inability to accurately predict postoperative function with consistently reliable prognostic factors.

[Prognostic factors of thyroid function following surgical therapy in Graves-Basedow's disease]

BACKGROUND

The goals of this work are to describe late thyroid function and to determine predictive factors of permanent hypothyroidism following surgery in Graves-Basedow's disease.

PATIENTS AND METHOD

From 1979 to 1999, 107 patients with hyperthyroidism due to Graves-Basedow's disease underwent subtotal thyroidectomy. We performed life-table analysis and calculated the cumulative incidence of hypothyroidism by means of the Kaplan-Meier's method. Survival (euthyroidism)within patients groups was compared using the Mantel-Cox method. Variables influencing long-term thyroid function were determined by estimating the Odds ratio with a logistic regression model.

RESULTS

The probability of euthyroidism among all 107 patients at 240 months was 51.4%.Age, gender, duration of both hyperthyroidism and antithyroid therapy and weight of resected thyroid tissue did not influence the eventual outcome. The weight of thyroid remnant was 5.4 (1.5)g and the conditional logistic regression analysis showed that weight of thyroid remnant was the only variable influencing long-term thyroid function. Hyperthyroidism relapsed in 5 patients.

CONCLUSIONS

In our experience,surgery represents a definitive alternative treatment with a risk of hypothyroidism within the first 2 years of 43.9%. The weight of thyroid remnant is the only variable influencing long-term thyroid function.

Surgical treatment of hyperthyroidism: a ten-year experience

Hyperthyroidism is treated either by antithyroid drugs, radioiodine (I131) or surgery. In Sweden, surgery is often performed in patients with large goiter or severe hyperthyroidism with infiltrative endocrine ophthalmopathy. To evaluate indications and results of surgical treatment, data from 380 patients operated on for hyperthyroidism at our department during 1986-1995 were analyzed. Twenty-six percent were referred for surgery because of failure of treatment with antithyroid drugs or I131. Ninety-one percent were subjected to subtotal thyroidectomy with a median remnant weight of less than 2 g. In the remaining patients, total thyroidectomy was performed. Transient vocal cord affection occurred in 2.6%, none of which was permanent. Prolonged postoperative hypocalcemia occurred in 3.1%, and permanent hypoparathyroidism in 1%. There was no difference in complication rate between subtotal or total thyroidectomy. In patients with Graves' disease, 5% worsened with regard to ophthalmopathy initially after surgery but later improved. Recurrent disease occurred in 2% of the patients, all of whom had undergone subtotal thyroidectomy. Surgery is not first-line therapy in all patients with hyperthyroidism. However, in experienced hands, surgery is a good therapeutic alternative that can be carried out with no mortality, few complications, and, provided that a minimal remnant is left, very few recurrences.

Management of Graves' disease in Australia

BACKGROUND

Surveys of physicians in Europe, the USA and elsewhere have shown marked international differences in the management of Graves' disease. There are no comparable data on clinical practice in Australia.

AIMS

To examine the current management of Graves' disease by Australian endocrinologists, particularly controversial aspects of management.

METHODS

A questionnaire, modified from previous studies, was sent to members of the Endocrine Society of Australia, asking how they would manage a 43-year-old female with a first episode of Graves' disease. Eight variations on this index case (goitre size, age, sex, severity, recurrent disease) were then introduced. A novel ninth variation, recurrent Graves' disease accompanied by moderate ophthalmopathy, was added.

RESULTS

Responses from 130 endocrinologists who regularly managed Graves' disease in adults were analysed. For the index case, medical treatment with antithyroid drugs was recommended by 81% of respondents and radioiodine by 19%. Most respondents also recommended medical treatment for a patient aged 19 years, a patient with a large goitre, no goitre or severe hyperthyroidism. For an older patient aged 71 years, however, 57% of endocrinologists recommended radioiodine, and the remainder medical treatment. For recurrent Graves' disease after previous medical treatment, 76% of respondents recommended radioiodine, 22% medical treatment and 2% surgery. By contrast, for an identical case accompanied by moderate ophthalmopathy, 54% recommended medical treatment, 27% surgery and only 19% radioiodine.

CONCLUSIONS

Most endocrinologists in Australia recommend medical treatment for a first episode of Graves' disease. Radioiodine is used mainly in older patients and for recurrent disease. In the presence of significant ophthalmopathy, most endocrinologists avoid the use of radioiodine.

The efficacy of thyroidectomy for Graves' disease: A meta-analysis

BACKGROUND

Surgery for Graves' disease was largely replaced in the mid-1900s by radioiodine and antithyroid drugs, due to the belief that they were more safe and effective. Since then, thyroid surgery has improved with preoperative drug therapy and modern operative techniques. Recent clinical studies of thyroidectomy for Graves' disease may not reflect outcomes accurately because of small sample size, especially when estimating ideal thyroid remnant size. The purpose of this study was to combine modern clinical trials and use meta-analysis to determine the overall efficacy of both total (TT) and subtotal thyroidectomy (ST) for Graves' disease, compare thyroid function and complications rates of TT and ST, and determine ideal thyroid remnant size.

METHODS

Meta-analysis was performed on published studies in which patients underwent either TT or ST for Graves' disease. Meta-analysis was performed by weighted least-squares linear regression. P < 0.05 was considered significant.

RESULTS

There were 35 studies comprising 7241 patients. Mean follow-up was 5.6 years. Overall, persistent or recurrent hyperthyroidism occurred in 7.2% of patients. TT was performed on 538 patients and hypothyroidism occurred in all cases. ST was performed in 6703 patients, 59.7% of whom achieved euthyroidism, 25. 6% became hypothyroid, and 7.9% had either persistent or recurrent hyperthyroidism. Permanent recurrent laryngeal nerve injury occurred in 0.9% of TT patients and 0.7% of ST patients (P = NS). Permanent hypoparathyroidism occurred in 1.6% of TT patients and 1.0% of ST patients (P = NS). There was an 8.9% decrease in hypothyroidism and 6.9% increase in euthyroidism for each gram of thyroid remnant (P < 0.0001 each).

CONCLUSIONS

Overall, thyroidectomy successfully treated hyperthyroidism in 92% of patients with Graves' disease. There were no cases of hyperthyroidism following TT. ST achieved a euthyroid state in almost 60% of patients with an 8% rate of persistent or recurrent hyperthyroidism. There was no significant difference in complication rates between TT and ST.

Results of subtotal thyroidectomy for Graves' disease

The objective of this study was to find the factors responsible for hypothyroidism after subtotal thyroidectomy for Graves' disease. Two hundred five patients who were operated on from July 1989 to December 1997 were studied. The mean age of patients was 33.4+/-11.0 (mean +/- SD) years, and 175 (85.4%) were female. Patients were prepared with an antithyroid drug and Lugol's solution preoperatively. Triiodothyronine (T3), thyroxine (T4), thyrotropin (TSH), thyrotropin-binding immunoglobulins (TBII) antimicrosomal antibodies (AMA = 100x 4(M-1)), and antithyroglobulin antibodies (ATA = 100x4(T-1)) were measured 1 week before patients were operated on. Operations were performed according to the standard procedure with 2.5x1x1 cm of thyroid tissue remaining on each side before approximating the thyroid capsule and pretracheal fascia. Hypothyroidism was defined by patients with overt hypothyroidism in laboratory data, and or with T4 to maintain T3 and T4. Two hundred two patients were checked 3 months after being operated on. Latent hyperthyroidism was found in 22, euthyroidism in 55, latent hypothyroidism in 91, hypothyroidism in 34 (16.8%) and none were in overt hyperthyroidism. After a follow-up period of 26.9+/-15 (mean +/- SD) months, 199 patients were reevaluated. Overt hyperthyroidism was found in 2 patients, latent hyperthyroidism in 12, euthyroidism in 97, latent hypothyroidism in 72, and hypothyroidism in 16 (8%). Factors having possible effects on hypothyroidism after longterm follow-up were analyzed. Patient's age, gender, body surface, premedicative T3 and T4, preoperative ATA, and TBII, and the weight of removed thyroid had no effect on the occurrence of hypothyroidism. Preoperative AMA levels, and finding more than 10 lymphoid infiltrations per 10 low-power fields (x40) were significantly different between the hypothyroid and nonhypothyroid groups. A high level of preoperative AMA was the only factor independently causing overt hypothyroidism in the follow-up period. Patients with high preoperative AMA levels have a higher risk of hypothyroidism if only 2.5x1x1 cm remnants are left on each side.

Total thyroidectomy for Graves' disease

BACKGROUND

Therapeutic options for treatment of hyperthyroidism caused by Graves' disease remain controversial. There are three main options: thiourea drugs, radioactive iodine ablation, and thyroidectomy. Each treatment has significant advantages and potential problems.

METHODS

The present study is a retrospective analysis of our experience with total thyroidectomy in Graves' disease. Sixty-two patients underwent this procedure in 11 years' time and were followed for a minimum of 2 years after surgery. All had measurement of total thyroxine, T3 uptake, and radioactive iodine (RAI) uptake and scanning. Sixty-three percent of all patients had some element of hyperthyroid eye signs. All patients were rendered euthyroid with pharmacologic therapy prior to surgery. Postoperatively, the patients were evaluated for improvement in eye signs, incidence of recurrent laryngeal nerve injury, and hypoparathyroidism.

RESULTS

None of the patients in this study have developed recurrent hyperthyroidism. All patients are maintained on levothyroxine. None of our patients incurred bilateral vocal cord paralysis. One patient (1.6%) demonstrated an immobile vocal cord more than 1 year following surgery. Ten patients (16%) demonstrated impaired mobility of one vocal cord in the immediate postoperative period. Nine of these patients recovered full vocal cord mobility within 6 months after surgery. Only one patient (1.6%) still required calcium and vitamin D therapy 1 year following surgery. However, in the immediate postoperative period, 23 patients (37%) required supplemental calcium and vitamin D. In 12 patients, calcium and vitamin D was discontinued within 1 month. In an additional 6 patients, calcium and vitamin D were discontinued within 4 months; 3 patients, within 6 months; and 1 patient, within 12 months after surgery. Incidental papillary carcinoma was found in 3 patients (5%).

CONCLUSIONS

Total thyroidectomy for Graves' disease is an effective and safe therapy. When performed by an experienced head and neck surgeon, it carries a low morbidity rate. It should be presented to patients as a therapeutic option within the context of a comprehensive discussion of the risks and benefits of radioactive iodine, pharmacologic therapy, and surgery.

Early recurrence of hyperthyroidism in patients with Graves' disease treated by subtotal thyroidectomy

Prerequisites for surgical treatment of Graves' disease are that it can be done safely and that it is associated with a low incidence of recurrent hyperthyroidism. Early recurrence is especially undesirable. We studied 728 patients with Graves' disease treated by subtotal thyroidectomy using multivariate analysis in order to determine the factors related to early recurrence. The following factors were analyzed: age, sex, duration of medical treatment, weight of resected thyroid tissue, thyroid remnant size, preoperative level of thyroid-stimulating hormone (TSH) binding inhibitory immunoglobulin (TBII), and antimicrosomal hemagglutination antibody (MCHA). "Early recurrence" was defined as TSH suppression observed within the first year after surgery and continuing for at least 6 months. A total of 106 patients (14.6%) had early recurrence. Statistical analyses were performed by the chi-square test for univariate analysis and a logistic model for multivariate analysis. Significant factors were thyroid remnant size, MCHA, and TBII. These results indicated that TBII and MCHA are related to early recurrence of hyperthyroidism, and smaller remnant size is recommended for patients with a high MCHA titer or a high TBII level (or both) in order to avoid early recurrence.

Human parathyroid blood supply determined by laser-Doppler flowmetry

The blood supply of 53 normal human parathyroid glands was studied with laser Doppler flowmetry in 45 patients undergoing operations on the thyroid and parathyroid glands. The inferior and superior thyroid arteries and other vessels that might supply the parathyroid glands were occluded so their contribution to parathyroid perfusion could be studied. Occlusion of the main trunk of the inferior thyroid artery resulted in a reduction of blood flow by one-third, and a similar reduction was obtained after occlusion of the superior thyroid artery. The results demonstrate that the blood supply to the parathyroid glands is not as dependent on the inferior thyroid artery as has previously been suggested but that other routes of blood supply may be equally or, in some cases, even more important.

Follow-up evaluation of patients with Graves' disease treated by subtotal thyroidectomy and risk factor analysis for post-operative thyroid dysfunction

Eight-year follow-up evaluation and analysis of factors related to postoperative thyroid dysfunction were made in 216 patients with Graves' disease treated by subtotal thyroidectomy. The postoperative status of thyroid function were as follows according to hypersensitive TSH level: 65 patients (30.1%) were euthyroid, 25 (11.5%) had overt hyperthyroidism requiring treatment, 14 (6.5%) had subclinical hyperthyroidism with normal thyroid hormone and suppressed TSH, 21 (9.8%) were overt hypothyroid requiring thyroid hormone replacement and 91 (41.1%) had latent hypothyroidism without hormone replacement. In order to know factors related to postoperative thyroid function, age, sex, preoperative levels of TSH receptor antibody (TRAb), thyroid antibody titers, degree of lymphocyte infiltration, duration of medical treatment, weight of the resected thyroid tissue and weight of the remnant thyroid tissue were determined. No factor except thyroid remnant and antimicrosomal antibody titer was related to postoperative thyroid function. The weight of remnant should be less than 6 g to avoid recurrent hyperthyroidism. As recurrence of hyperthyroidism was observed more than 5 yr after surgery, long follow-up is needed.

Surgery for hyperthyroidism: hemithyroidectomy plus contralateral resection or bilateral resection? A prospective randomized study of postoperative complications and long-term results

Fifty consecutive patients undergoing surgical treatment for hyperthyroidism were randomized to have either bilateral subtotal resection (n = 23) or hemithyroidectomy plus contralateral resection (n = 27). No significant differences in operating time or intra-operative bleeding were found. No postoperative bleeding and no temporary or persistent recurrent laryngeal nerve paralysis occurred. Four patients who underwent bilateral resection and 2 patients who had hemithyroidectomy resection needed temporary calcium supplementation, and the serum calcium concentrations were slightly lower during the first few postoperative days in the patient undergoing hemithyroidectomy/resection. No persistent hypocalcemia occurred in either of the groups. At follow-up 3-4 years (mean 3.6 years) postoperatively, 1 patient in the bilateral resection group developed recurrent hyperthyroidism; no patients in the hemithyroidectomy/resection group developed recurrent hyperthyroidism. Twelve (44%) patients in the hemithyroidectomy/resection group and 8 (35%) patients in the bilateral resection group needed thyroxine supplementation because of a rise in thyroid stimulating hormone concentration combined with clinical signs of hypothyroidism that developed during follow-up. Hyperthyroidism can be treated by hemithyroidectomy plus contralateral resection without increasing the risk of complications. The results also suggest that when using this method, a slightly larger thyroid remnant should be left to avoid an increase in the incidence of hypothyroidism postoperatively.

Retrospective analysis of prognostic factors affecting the thyroid functional status after subtotal thyroidectomy for Graves' disease

To determine the factors causing thyroid dysfunction after surgery for Graves' disease, we studied 321 patients who underwent subtotal thyroidectomy during the 7-year period from 1981 to 1987. Thyroid functional status was evaluated biochemically and the patients were divided into four categories: recurrent hyperthyroidism, euthyroidism, latent hypothyroidism, and hypothyroidism. The following factors were analyzed: sex, age at onset of the disease, indication for surgery, serum titer of antimicrosomal hemagglutination antibody (MCHA), weight of resected thyroid tissue, size of remnant thyroid relative to body surface area, pathological findings of lymphoid follicles, and lymphocytic infiltration in the thyroid tissue. Probabilities of failure (recurrent hyperthyroidism and hypothyroidism) were estimated by the Kaplan-Meier method. Prognostic factors for failure were identified by using Cox's proportional hazards model. The incidence of hyperthyroidism and hypothyroidism 5 years after subtotal thyroidectomy was 16.2% and 9.6%, respectively. Significant factors for hyperthyroidism were relatively large thyroid remnant, high serum titer of MCHA (greater than or equal to 1:3200), and age at onset of the disease less than 20 years. The significant factor for hypothyroidism was severe lymphocytic infiltration. The level of postoperative thyroid stimulating hormone (TSH)-binding inhibition immunoglobulins (TBII) in patients with recurrence was significantly higher than in patients in remission. It is reasonable to determine the amount of remnant thyroid tissue in relation to patient body surface area. Although subtotal thyroidectomy can induce immunological remission by reduction of antigen, if the remission disappears, that is if TBII increases, recurrence of hyperthyroidism may develop even in patients without the unfavorable factors.

Natural course of Graves' disease after subtotal thyroidectomy and management of patients with postoperative thyroid dysfunction

The Natural course of Graves' disease after subtotal thyroidectomy was studied in 67 patients who had subtotal thyroidectomy for Graves' disease and did not receive any medical treatment for 8 to 12 years after surgery. Postoperative thyroid status was determined by serum free thyroxine (T4), free triiodothyronine (T3), and thyrotropin (TSH) levels in the first period (1 year after surgery), second period (3.9 +/- 1.0 years), and third period (8.8 +/- 1.5 years). Serum thyroid stimulating antibody (TSAb) and TSH binding inhibitor immunoglobulin (TBII) activities were also measured. A total of 53 patients (79%) changed thyroid status during the observation period. One year after surgery, 50 percent of euthyroid subjects developed abnormal thyroid function in the next period. Reversible latent hypothyroidism was the most common type of thyroid dysfunction seen in up to 46% of patients. Interestingly, hyperthyroidism and hypothyroidism that developed in the postoperative period were temporary disorders in most cases. Serum TSAb and TBII activities did not help predict the postoperative changes of thyroid status. Our study indicates that the instability of the thyroid function is common after subtotal thyroidectomy.