Calculation of the radioiodine dose for the treatment of Graves' hyperthyroidism: is more than seven-thousand rad target dose necessary?

Some authors recently suggested a significant increase in the target dose of radioiodine treatment in Graves' disease. The aim of the present study was to investigate the impact of thyroid gland mass on the success rate of radioiodine treatment. For this purpose, the thyroid function of 105 consecutive Graves' patients was assessed 6 and 12 months after a 131I treatment and correlated to the gland mass. The patients were categorized according to the gland mass into small (< or = 30 g; 19 patients), medium size (31-50 g; 40 patients), and large size (> 50 g; 46 patients) groups (S, M, L groups, respectively). None of the patients received more than a 10,000-rad (100-Gy) target dose. During the calculation of administered 131I activity, late uptake measurement has also been routinely used, in addition to the usual maximal uptake parameter. The established effective half-life of 131I was highly variable (5 +/- 1.2 days; range: 2-7.6 days) and could not be predicted based on other clinical data without measuring an extended radioiodine uptake curve of the given patient. However, the correlation between the administered activity calculated from the complete set of uptake values and that of only a single late one was excellent (r = 0.99). Six months after the 131I treatment, hyperthyroidism was cured in 81% of patients with small and medium size thyroid glands, with 62% euthyroid and 19% hypothyroid ratios respectively. In the early phase of study for large goiters, the same linear mass activity function was used during calculation as in smaller glands. In these 17 patients the nonhyperthyroid result was comparable to the results of treatment of the small and medium size gland groups only after 1 year (77%), but the 6-month success rate was significantly lower (53%; p < 0.05). After obtaining these results, the usual 7000-rad target dose was increased to 8000-10,000 rad (depending on the gland mass) in another group of 29 patients with large thyroid glands that result in an acceptable 6-month success rate of 72%. In conclusion, instead of the "mCi 131I/g gland mass/maximal uptake" dose calculation, we suggest a method in which (1) the late 131I uptake measurement is taken into account and (2) for large goiters there is an additional dose adjustment, ie, increase is needed over the usual linear, size driven calculation. No overall increase of target dose over 10,000 rad is necessary if no antithyroid medication is given shortly before 131I treatment.

The role of technetium-99m methoxyisobutylisonitrile scintigraphy in the differential diagnosis of cold thyroid nodules.

Various diagnostic techniques have been successfully used in the clinical management of cold nodules; however, the decision on whether to employ surgery or a conservative treatment is not always easy. This study was designed to appraise the diagnostic value of technetium-99m methoxyisobutylisonitrile (MIBI) scintigraphy in the assessment of cold nodules detected using (99m)Tc-pertechnetate. Fifty-two patients were included in the study. All had already been selected for surgery, based on their clinical and laboratory findings, including fine-needle aspiration biopsy. The total number of cold nodules on (99m)Tc-pertechnetate scans was 59. The thyroid scan was performed 20-40 min after i.v. injection of 400 MBq of (99m)Tc-MIBI. Uptake of MIBI in thyroid nodules was compared with that in the surrounding normal thyroid tissue, and a score of between 0 and 3 was assigned to each nodule as follows: 0, cold; 1, decreased; 2, equal; 3, hot. Definitive histology revealed nodular goitre in 24 cases, adenoma in 19, thyroiditis in 1, differentiated cancer in 12, medullary cancer in 2, and anaplastic cancer in 1. None of the degenerative nodules were hot on MIBI scan, while the adenomas showed a variety of MIBI imaging patterns, most frequently the score 3 pattern. In the diagnosis of differentiated thyroid cancer the sensitivities of score 3 and score 2+3 MIBI uptake patterns were 83% (10/12) and 100%, respectively. The score 3 MIBI uptake pattern had a specificity of 100% and a positive predictive value of 100% with respect to thyroid (benign and malignant) neoplastic diseases, whereas a specificity of 72% and a positive predictive value of 43% were observed in the detection of differentiated cancer. After a cold nodule had been detected using (99m)Tc-pertechnetate, a second scan with high MIBI uptake increased by 7.8 times the probability that this nodule would be a differentiated cancer. In conclusion, (99m)Tc-MIBI scintigraphy is a useful method in the differential diagnosis of cold thyroid nodules if the primary aim is to differentiate degenerative from neoplastic diseases rather than to differentiate benign from malignant nodules. High MIBI uptake considerably increases the probability of a differentiated thyroid cancer and facilitates immediate surgical removal, while decreased uptake actually excludes it. We suggest a combination of fine-needle aspiration biopsy and MIBI scan as a routine diagnostic approach to cold thyroid nodules.

Parameters of respiratory burst and arachidonic acid metabolism in polymorphonuclear granulocytes from patients with various thyroid diseases.

The oxidative processes (oxygen consumption, superoxoid anion generation, arachidonic acid cascade) of human polymorphonuclear granulocytes (PMNs) obtained from patients suffering from thyroid disorders of autoimmune origin (Graves' disease and Hashimoto's thyroiditis), and non autoimmune origin (toxic adenoma) were investigated. All Graves' and toxic adenoma patients were hyperthyroid. Hashimoto's thyroiditis patients were euthyroid. Healthy age and sex matched volunteers served as controls. The results are as follows: 1) In PMNs from both hyperthyroid groups (Graves' disease and toxic adenoma), independently from the autoimmune origin of the disease, a significantly increased Antimycin A sensitive mitochondrial oxygen consumption and a slightly increased superoxide anion generation were detected. 2) In both autoimmune thyroid disease groups (Graves' disease and Hashimoto's thyroiditis)--depending on the functional state of the thyroid gland--a significantly altered intracellular killing activity was measured. 3) An increased arachidonic acid cascade--triggered by opsonized zymozan (OZ)--was detected in both autoimmune thyroid diseases. The increased arachidonic acid cascade was sensitive to phospholipase A2 inhibiting Mepacrin treatment. 4) The PMNs from both autoimmune thyroid diseases produced large amount of leukotriens (LTs)--LTC4 and LTB4--after stimulation through their Fc receptors but the synthesis of prostagalandins (PGs) has not changed. There are no data indicating local, specific effects of circulating leukotriens in the thyroid gland itself, but based on authors' data, their general, regulating role on both the endocrine-- as well as on the immune system--seems to be plausible.

Some aspects of hypothyroidism in elderly.

The frequency of hypothyroidism does not diminish with age but there is a considerable change in its clinical pattern. The data of 169 patients treated with primary hypothyroidism were processed by means of computer analysis. They were put, in accordance with their basic diseases, into 5 groups: idiopathic (50.3%); chronic thyroiditis (26.6%); as a result of the ablative treatment of Graves' disease (17.2%); nodular goitre (4.7%) and thyroid malignancy (1.2%). According to age, the patients fell into 4 groups. III patients were between 50 and 90 years of age. In most cases the identification of the disease was belated. The usual symptoms that might lead to the consideration of hypothyroidism are edema not reacting to diuretics, anemia, and high blood lipid values. In 18 patients with a previous case history of immunothyroiditis, the cultured monocyte monolayers were examined for the activity of the specific and the scavenger LDL receptors and for the intracellular breakdown of LDL.

Atypical clinical features of hypo- and hyperthyroidism in elderly age.

The clinical features of senile hypothyroidism and hyperthyroidism differ from the general characteristics of these conditions. This may be explained primarily by the changed response of peripheral tissues to thyroid hormones. Because of the atypical clinical symptoms the recognition of these conditions meets difficulties and, in general, occurs late. Therapy raises further special questions considering primarily cardiac complications and other accompanying diseases (for instance arteriosclerosis, osteoporosis, diabetes mellitus.). The authors analyse data of 171 hypothyroid and 219 hyperthyroid patients as a function of age, primary disease, and the most often occurring impulse generation, impulse conduction disorders.

A possible competition between 5'-monodeiodination of thyroxine and the respiratory burst in human granulocytes.

Thyroxine (T4) pretreatment of A 23187-stimulated human granulocytes in 10(-5)-10(-6) M concentration range inhibited the superoxide anion production of these cells. T4 increased the level of oxidized form of glutathione, whereas the intracellular level of the reduced form decreased. A similar alteration in the ratio of the oxidized to reduced forms of glutathione was detected in granulocytes during yeast cell phagocytosis. In addition, conversion of T4 to triiodothyronine (T3) was also inhibited during phagocytosis. A possible competition between 5'-monodeiodination of T4 and the oxidative burst of human granulocytes is discussed.

The pathogenetic connection between Graves' disease and chronic lymphocytic thyroiditis. (The role and incidence of thyroid stimulating antibodies).

Antibody-positivity to thyroid specific antigens (Htg, microsomal) and/or lymphocytic infiltration of the gland's parenchyma were observed in 207 (55%) of 377 patients with Graves's disease. Only in 48 (12.7%) of the cases were the findings in agreement with the criteria of chronic lymphocytic thyroiditis. Human thyroid stimulating antibody (HTSab) was detected in 135 (65%) of these 207 patients. In cases of Graves' disease associated with chronic lymphocytic thyroiditis, this proportion was found to be as high as 89.6% and attained even 100% in cases of Hashitoxicosis (39 patients). The presence of HTSab thus seems to form one of the features of patients with Hashitoxicosis. Infiltrative ophthalmopathy also showed a remarkably high incidence (59%) in this porcess. The typical prevalence of Graves' disease in females in the present material attained a 15:1 female-to-male ratio when the disease was associated with chronic lymphocytic thyroiditis. The results of the present study suggest that chronic lymphocytic thyroiditis associated with Graves' disease promotes the formation of thyroid stimulating antibodies.

Inhibition of spontaneous E-rosetting by antithymocyte globulin in Graves disease.

The number of thymus-dependent (T) lymphocytes and the concentrations of antithymocyte-globulin causing 25% inhibition of E-rosetting were determined in 40 cases of Graves disease. No significant difference in T-lymphocyte count was found between the test groups and the control group. An increased resistance of T-lymphocytes to antithymocyte globulin was found in Graves disease, particularly in its form marked by progressive ophthalmopathy. The increase in resistance was significant in the first five years of the disease.