Hypothyroidism after thyroidectomy for Graves's disease: a search for an explanation

Incidences of Hypothyroidism Associated With Surgical Procedures for Thyroid Disorders: A Nationwide Population-Based Study

Background and Aim: Limited information available about different types of thyroid surgeries with risk for postoperative hypothyroidism. This study aimed to investigate the risk of developing early and late-onset postoperative hypothyroidism in patients with thyroid disorders. Methods: We used a large cohort data from the Taiwan National Health Insurance Research Data Base (NHIRDB) and identified 9,693 (9, 348) patients from January 1998 to December 2010, admitted for thyroid disorder surgeries. We used the surgical procedures time as the index date. Our observational retrospective cohort study excluded the subjects diagnosed with hypoparathyroidism and hypothyroidism before any surgeries. We analyzed the data using the Cox regression model to calculate the hazard ratio. Result: Postoperative hypothyroidism associated with bilateral-total (HR, 4.27; 95% CI, 3.32-5.50), one-side total and another subtotal (HR, 3.16; 95% CI, 2.59-3.86), bilateral-subtotal (HR, 1.65; 95% CI, 1.37-1.98), and unilateral-total (HR, 1.17; 95% CI, 0.95-1.44) surgical procedures. The time intervals for thyroid disorders were 320 cases developed postoperative hypoparathyroidism in eight weeks, 480 cases the second month, and 1000 cases in the first year after surgery. Conclusion: Findings suggest that thyroidectomy was associated with transient postoperative hypothyroidism in thyroid disorder patients. The bilateral-total surgical procedure was strongly associated with temporary postoperative hypothyroidism.

Spontaneous Hypothyroidism in the Follow up of Graves Hyperthyroid Patients Treated with Antithyroid Drugs

AIM

Spontaneous hypothyroidism may follow the natural course of Graves disease (GD) after treatment with antithyroid drugs (ATD).

METHODS

We studied retrospectively 139 remitted Graves hyperthyroid patients treated with ATD, with a follow-up period of 17.5 years (range 6 to 25 years). Elevated serum concentration of thyroid-stimulating hormone and low serum thyroxine concentrations confirmed the diagnosis.

RESULTS

Thirteen patients (median age, 41 years; 26 to 48 years) developed spontaneous hypothyroidism, 4 to 144 months (median, 48 months ) following withdrawal of ATD. The prevalence of hypothyroidism was 9.3% and the incidence was 2.3% per year (13/ 563.6 patients/year of observation). There was no association with types of drugs used or the regimens. Spontaneous hypothyroid patients showed elevated titers (P = 0.02) of serum antithyroid peroxidase antibody (TPOAb) at the end of treatment with ATD, compared with the titers found at the beginning. These patients also had higher titers of TPOAb (P = 0.01) in relation to euthyroid patients. In contrast, the changes in serum antithyroglobulin antibody titers were not significant.

CONCLUSIONS

Because of the shift from euthyroidism to spontaneous hypothyroidism, GD patients demanded a strict follow up after ATD therapy. It seems that there is an effect of TPOAb on thyroid destruction.

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.

Analysis of antibody-dependent cell-mediated cytotoxicity in autoimmune thyroid disease

There is no consensus on the role of antibody-dependent cell-mediated cytotoxicity (ADCC) in autoimmune thyroid disease; recent reports have suggested that antibodies mediating ADCC are found particularly in patients with primary myxoedema, occur less frequently in Hashimoto's thyroiditis and are absent in Graves' disease. Using an ADCC assay with a single source of effector and target cells, and expressing results as lytic units, we have found antibodies capable of mediating ADCC in 9 of 17 patients with primary myxoedema, 9 of 22 patients with Hashimoto's thyroiditis and 6 of 22 patients with Graves' disease. There was no significant difference between the groups in this distribution. Mean levels of ADCC activity were not significantly different comparing primary myxoedema and Hashimoto's thyroiditis patients, although levels were lower in Graves' disease patients compared to those with Hashimoto's thyroiditis (P < 0.05). There was no correlation between TPO antibodies (total IgG or IgG subclasses) measured by ELISA and ADCC activity. These results suggest that thyroid antigens besides TPO are involved in ADCC and that antibodies mediating ADCC are not restricted to subgroups of patients with autoimmune thyroid disease.

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.

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.

Immunological effects of Graves' disease therapy

Graves' disease is caused by thyroid stimulating antibodies and is accompanied by other autoimmune phenomena predisposing ultimately towards hypothyroidism. Antithyroid drugs directly alter the natural history of the condition, causing a remission in 50% of cases; part of this is likely to be due to their immunomodulatory effect. Surgery and radioiodine treatment are also accompanied by immunological changes which may affect outcome. In particular, some cases of hypothyroidism may be the result of a hastening of the natural progression to destructive thyroiditis.

Current treatment of Graves' disease

In this review we have described the rationale for the appropriate treatment of patients with Graves' disease. Because the etiology of this disorder remains obscure, its management remains controversial. Since antithyroid drugs and radioiodine became readily available in the early 1950s, they have been widely used for the treatment of thyrotoxicosis, and the number of cases treated surgically has markedly decreased. However, almost four decades of experience have disclosed an unexpectedly high incidence of delayed hypothyroidism after radioiodine treatment and a low remission rate after antithyroid therapy. As a result, surgery is again being advocated as the treatment of choice. The three modalities of treatment have different advantages and disadvantages, and selection of treatment is of importance. In principle, we believe that for most patients a subtotal thyroidectomy should be performed after the patient has been rendered euthyroid by antithyroid drugs. We attempt to leave a thyroid remnant of 6 to 8 gm.

Place of radioactive iodine in treatment of thyrotoxicosis

The effect of treatment of thyrotoxicosis with drugs, radioactive iodine, or surgery in different age groups is reviewed. In Graves' disease and toxic multinodular goitre the remission rate is about 40-50% after antithyroid drugs, but these drugs have little effect in toxic adenoma. Hypothyroidism developed in 35-49% of patients who had had thyroidectomy, and the risks of operation are high. The risk of malignant disease and genetic abnormalities was not significantly greater after treatment with radioactive iodine in any age group. In general, treatment with radioactive iodine should have priority over thyroidectomy at all ages.

The management of thyroid swellings

All cold solid nodules should be pursued relentlessly and all cancers of the thyroid, with the possible exception of anaplastic tumours, should be treated radically. The majority of differentiated cancers of the thyroid may carry a good prognosis but those which recur constitute a group of cases which are very difficult to manage and cure.

Late onset hypothyroidism after subtotal thyroidectomy for hyperthyroidism: implications for long term follow-up

A follow-up register has been used in Aberdeen and Dundee to record early and late onset hypothyroidism occurring in a large population of post-thyroidectomy patients treated for hyperthyroidism. In one centre, in a total of 1170 patients, the prevalence of postoperative hypothyroidism, at the time of entry to the register, was 41 per cent. Of these early cases of hypothyroidism 93 per cent occurred within 18 months of operation. Results are presented from a 12-year prospective study of patients treated in two centres, who were euthyroid when entered on the follow-up register. In one centre, based on 683 patients, the 10-year incidence of late onset hypothyroidism estimated by actuarial methods was 7.4 per cent (95 per cent confidence limits, 3.8-11.1); in the other centre with 156 patients the 5-year incidence was 10.8 per cent (95 per cent confidence limits, 3-18.6). The minimum predicted annual incidence is 1 per cent. Large thyroid remnants do not protect some patients against early or late postoperative hypothyroidism but do lead to an increased risk of recurrent hyperthyroidism. Hypothyroidism after subtotal thyroidectomy for hyperthyroidism shows a bimodal pattern and this study emphasizes the need to maintain life-long follow-up.

Comparison of thyroid function in mice after various injected activities of 123I, 125I and 131I

The radiotoxicity of 123I, 125I and 131I to the thyroid gland was compared in groups of mice subjected to activities of the three isotopes ranging from 10(-2) to 10(2) MBq. The thyroid function was determined fifteen months later on the basis of the 24-hour uptake of a tracer activity of 131I. A reduction in uptake to 20 per cent of the control value for untreated mice was found for mice injected with 35 MBq of 123I, 13 MBq of 125I and 2 . 2 MBq of 131I. On estimating the average absorbed dose in different parts of the thyroid by means of a refined method of dose calculation, that found in the cell layers surrounding the follicles seemed to be most indicative for impairment of thyroid function.

Hypothyroidism as a late sequela in patient with Graves' disease treated with antithyroid agents

In 1971, thyroid function was evaluated in 15 unselected patients whose only therapy for diffuse toxic goiter was a course of thionamide drug treatment completed 20-27 yr earlier. One patient was frankly hypothyroid by clinical and laboratory criteria. The remaining 14 patients appeared clinically euthyroid and had a normal serum thyroxine (T(4)) concentration and thyroid radioiodine uptake (RAIU). Nevertheless, only 6 of 14 appeared to be entirely normal according to more refined criteria. The serum thyrotropin (TSH) concentration was markedly elevated in one patient and above the normal range (1.6+/-2.0; mean+/-2 SD) in five others. Thyroid stimulation with exogenous TSH revealed subnormal responses of the serum T(4)I, RAIU, or both, in 7 of 11 patients tested. An abnormal iodideperchlorate discharge test was found in 5 of 10 patients and appeared most abnormal in patients with abnormal RAIU responses to TSH. Fluorescent antimicrosomal antibody was found in the serum of 12 of the 15 patients, in contrast to an expected frequency of 7% in normal individuals of the same age. By the time a second major follow-up study was completed in 1978, two additional patients had become frankly hypothyroid. A third subject met accepted criteria for subclinical hypothyroidism. One of these subjects had had a clearly elevated serum TSH concentration in 1972, and the remaining two had exhibited the highest responses of serum TSH (36, 26 muU/ml) to thyrotropin-releasing hormone among 10 patients tested in 1972. One patient developed recurrent thyrotoxicosis in 1978, 25 yr after the onset of his first and only other apparent episode of hyperthyroidism. This patient was the only one who demonstrated a subnormal response to thyrotropin-releasing hormone in 1972. The remaining nine subjects that could be studied in 1978 exhibited varying combinations of abnormalities of thyroid function. It is concluded that progressive failure of thyroid function is a common occurence in long-standing Graves' disease, and it is suggested that this results from concomitant chronic thyroiditis. We postulate that this inherent tendency toward thyroid failure is exaggerated by surgery or radioactive iodine, explaining the progressive increase in, and inordinate frequency of, hypothyroidism after ablative modes of therapy in diffuse toxic goiter.

Raised total thyroxine and free thyroxine index but normal free thyroxine. A serum abnormality due to inherited increased affinity of iodothyronines for serum binding protein

2 people from different families had high levels of serum-thyroxine (T4) and a high free T4 (FT4) index but a normal serum triiodothyronine (T3) and serum-reverse-T3 (rT3). The abnormal serum thyroid hormone profile appeared to be inherited in an autosomal dominant manner. Serum-FT4 in affected relatives was normal. The increases in serum-T4 and FT4 index are explained on the basis of an observed increase in affinity of T4 for thyroxine-binding globulin, thyroxine-binding prealbumin, and albumin. The FT4 index did not reflect the true concentration of circulating free T4 in these cases. Thyroid function in the propositi was normal and the results of T4, T3, and rT3 kinetic studies accorded with increased binding of T4 by serum proteins and normal binding of the other iodo-thyronines. This "euthyroid high total T4, normal T3 syndrome" should be kept in mind during diagnostic evaluation of thyroid function.

Histometry of lymphoid infiltrate in the thyroid of primary thyrotoxicosis patients. Relation of extent of thyroiditis to preoperative drug treatment and postoperative hypothyroidism

The thyroids of primary thyrotoxicosis patients prepared for partial thyroidectomy with propranolol contained much more lymphoid infiltrate than those prepared with carbimazole. 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 factor in predicting hypothyroidism after subtotal thyroidectomy for primary thyrotoxicosis.

Whither thyrotoxicosis?

For 30 years the thyrotoxic patient has been subjected to a plurality of treatments by surgery, radio-iodine and long term anti-thyroid drugs. These therapies have been accepted as complementary to the needs of the individual patient, without regard for long term results or the economic situation as it affects both patient and hospital services. In the context of surgical treatment which is now available, it is suggested that the advantages of operation over other therapies presage a reversion to surgery as the treatment of choice.