Effect of therapy on the serum thyroglobulin concentration in patients with toxic diffuse goiter, toxic nodular goiter and toxic adenoma

Serum thyroglobulin (S-Tg) was measured in 104 patients with thyrotoxicosis, 59 of whom had toxic diffuse goiter (Graves' disease), in 30 with toxic nodular goiter and in 15 with toxic adenoma. Before treatment, most patients had increased S-Tg concentrations, regardless of what type of thyrotoxicosis they had. After therapy the course of the S-Tg varied, two major patterns being observed: the S-Tg concentration increased in some patients but decreased in others, although no relationship could be found between these patterns and the outcome of therapy, the presence or absence of thyroglobulin antibodies (Tg-ab) or changes in the Tg-ab titer. However, the median pretreatment concentrations of S-Tg were significantly higher in patients with toxic nodular goiter and toxic adenoma than in those with toxic diffuse goiter (p less than 0.001 and p less than 0.05, respectively), but did not differ significantly between patients with toxic nodular goiter and toxic adenoma. The lowest posttreatment S-Tg concentrations were found after surgery, irrespective of type of thyrotoxicosis. The median pretreatment and posttreatment S-Tg concentrations in patients with toxic diffuse goiter who relapsed, did not differ from those patients in remission. This was also true of patients with toxic nodular goiter. In both groups, however, there was a tendency towards higher pretreatment S-Tg values in patients who subsequently relapsed. Serial determinations of S-Tg, on the other hand, are of limited value in predicting the risk of recurrence, independent of which type of thyrotoxicosis is involved.

Lower serum free thyroxine (T4) levels in painless thyroiditis compared with Graves' disease despite similar serum total T4 levels

Serum total T4 (T4), total T3 (T3), free T4 (FT4), free T3 (FT3), and T4-binding globulin concentrations and T3 resin uptake values were measured in 17 women with thyrotoxicosis due to painless thyroiditis (PT) and compared with the same parameters in 17 women with thyrotoxicosis due to Graves' disease (GD) with similar serum T4 levels. The mean serum T3 resin uptake value and T3, FT4, and FT3 concentrations in the PT patients were significantly lower than those in the GD patients. The mean serum T4-binding globulin concentration [20.2 +/- 4.2 (+/- SD) microgram/mL] in patients with PT did not differ significantly from those in patients with GD (18.0 +/- 2.6 micrograms/mL) and normal euthyroid women (21.9 +/- 4.0 micrograms/mL). The serum T3 to T4 (nanogram per microgram) ratio was higher than 20 in 14 GD patients, but lower than 20 in all patients with PT, whereas the individual serum FT3 to FT4 ratio values considerably overlapped in the 2 groups. In patients with PT, FT4 correlated well with T4 at various times during the clinical course. These findings indicate that the elevation in serum FT4 in patients with PT is mostly due to the increase in circulating T4 levels, whereas GD patients also have some diminution in T4 binding. The serum T3 to T4 ratio, but not the FT3 to FT4 ratio, may be helpful for differentiation between the two diseases.

Application of an immunoradiometric assay for thyrotrophin in evaluation of thyroidal and nonthyroidal disease states

We evaluated an immunoradiometric assay for serum TSH (IRMA-TSH) and compared it with established indices of thyroid function in 208 patients with either frank thyroid disease, conditions of abnormal thyroxine protein binding, or conditions which are known to produce discordant thyroid results, viz. pregnancy or estrogen treatment and nonthyroidal illness (NTI). As expected, a wide scatter of TSH results was found in treated thyroid disease: 53 patients (53%) from both groups (initially hypo- or hyperthyroid) had TSH values less than 0.5 mU/l, but only one was considered to be clinically mildly toxic. All the pregnant, estrogen-treated and abnormal thyroxine protein-binding patients had TSH results within the reference range 0.5-6.0 mU/l, except one familial dysalbuminemic hyperthyroxinemia (FDH) patient (T4 level, 178 nmol/l) lost to follow-up with a TSH level of 8.5 mU/l, and one euthyroid, low-TBG patient being treated inappropriately with thyroxine, with a TSH level less than 0.5 mU/l. All the untreated thyrotoxic patients and 15 (26.3%) of the NTI patients had TSH results of 0.5 mU/l or lower. Because of this high incidence of low TSH levels in euthyroid NTI, we cannot recommend this IRMA-TSH as the initial test of thyroid function.

Thyrotoxicosis caused by functioning metastatic thyroid carcinoma. A rare and elusive cause of hyperthyroidism with low radioactive iodine uptake

A patient with progressively worsening thyrotoxicosis, refractory to medical therapy, is described. Repeated measurements of thyroidal RAI uptake over a 13 month period were low consistently and could not be explained by iodine ingestion, thyroiditis, or administration of exogenous thyroid hormone. An I-131 scan ultimately revealed striking activity at the base of the skull, reflecting ectopic excessive production of thyroid hormone by a solitary functioning metastatic thyroid carcinoma. The thyrotoxic state resolved after large doses of therapeutic I-131. Typical features of this rare cause of hyperthyroidism are discussed.

'Apathetic' thyrotoxicosis presenting with hypercalcaemia and spurious normalization of serum thyroid hormone levels

A patient with thyrotoxicosis presented with weight loss and hypercalcaemia, leading to an erroneous diagnosis of occult malignant disease. Intercurrent illness and drug treatment of hypercalcaemia in this patient caused a depression of circulating thyroid hormone levels, leading to a delay in diagnosis. Radionuclide studies of thyroid function, in contrast, consistently suggested a thyrotoxic state. It is suggested that in this situation, radionuclide studies may give a more accurate assessment of thyroid status than biochemical tests, which may be difficult to interpret in the presence of non-thyroidal illness.

Glucose intolerance in thyrotoxicosis roles of insulin, glucagon and somatostatin

The responses in plasma glucose, insulin, C-peptide, glucagon and somatostatin to an oral glucose load were studied in 10 thyrotoxic patients and 10 matched euthyroid controls. The thyrotoxic patients had higher mean fasting plasma glucose (P less than 0.05) and responded to oral glucose with an earlier peak at 30 min which was higher than the corresponding glucose level in the controls (P less than 0.05). Impaired glucose tolerance was found in 3 patients. Fasting insulin and C-peptide levels were normal in the thyrotoxic patients when corrected for the higher glucose levels. Following glucose ingestion, there was no significant difference between the areas under the insulin or C-peptide curves in patients and controls, but Seltzer's insulinogenic index was reduced in the patients (P less than 0.01) suggesting an impaired pancreatic B-cell response to oral glucose. Mean basal glucagon was normal in the thyrotoxic patients. However, while in the controls plasma glucagon became suppressed following glucose ingestion (P less than 0.0001), no significant suppression was found in the patients. In the thyrotoxic patients, mean basal somatostatin was normal, but the area under the somatostatin curve following glucose ingestion was significantly increased (P less than 0.02). Our findings suggest that decreased glucagon suppression and impaired insulin response after glucose ingestion are involved in glucose intolerance in thyrotoxicosis. Enhanced somatostatin responses to oral glucose in thyrotoxicosis may have contributed to the observed impairment in pancreatic B-cell responsiveness.

Amiodarone: a common source of iodine-induced thyrotoxicosis

Amiodarone, a iodine-rich drug widely used in the treatment of tachyarrhythmias, represents one of the most common sources of iodine-induced thyrotoxicosis. The data concerning 58 patients with amiodarone-iodine-induced thyrotoxicosis (AIIT) were analyzed in the present study. Prevalence of AIIT was higher in males than in females (M/F = 1.23/l). Thyrotoxicosis occurred either during treatment with or at various intervals after withdrawal of amiodarone. AIIT developed not only in patients with underlying thyroid disorders, but also in subjects with apparently normal thyroid gland. Classical symptoms of thyrotoxicosis were often lacking, the main clinical feature being a worsening of cardiac disorders. Biochemical diagnosis of AIIT was established by the finding of elevated serum total and free triiodothyronine levels, since elevated serum total and free thyroxine could be found also in euthyroid amiodarone-treated subjects. Twenty-four-hour thyroid radioiodine uptake was very low or undetectable in AIIT patients with apparently normal thyroid glands, while it was inappropriately elevated in patients with underlying thyroid disorders, despite iodine contamination. The role of autoimmune phenomena in the pathogenesis of AIIT appeared to be limited, because circulating thyroid autoantibodies were undetectable in AIIT patients without underlying thyroid disorders or with nodular goiter. Conversely, humoral features of thyroid autoimmunity were mostly found in AIIT patients with diffuse goiter. Treatment of AIIT appeared to be a difficult challenge. Among the 11 patients given no treatment, thyrotoxicosis spontaneously subsided in the 5 patients with apparently normal thyroid gland, whereas the 6 patients with nodular or diffuse goiter were still hyperthyroid 6-9 months after discontinuation of the drug. The administration of high doses (40 mg/day) of methimazole alone proved to be ineffective in most (14/16) patients given this treatment. Twenty-seven patients were treated by methimazole combined with potassium perchlorate (1 g/day). With one exception, euthyroidism was restored within 15-90 days in all cases with underlying thyroid abnormalities, and within 6-55 days in subjects with apparently normal thyroid gland. Thus, the combined treatment appears to be the most effective one, but, due to the potential toxicity of potassium perchlorate, it should be reserved to patients with severe thyrotoxicosis and should be carefully monitored.

Diagnostic value of free triiodothyronine in serum

Serum free T3 concentration has been assessed in various thyroid conditions by a T3 analog method and the results compared with those obtained by equilibrium dialysis in the same individuals. The methodology is easy to perform and reproducible. FT3 determination appears to be especially valuable in detecting borderline thyrotoxicosis as in cases previously cured from thyrotoxicosis but suspected of relapse, or in nontoxic goitrous patients overtreated with T4.