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In the present study we have recorded visual evoked cortical potentials (VECP) in 88 patients affected by autoimmune thyroid disease and thyroid-associated ophthalmopathy (TAO) without clinical signs of optic neuropathy. At the time of ophthalmological examination, 37 of these patients were hyperthyroid, 41 were euthyroid, and 8 were hypothyroid; 2 were not assessed. Twenty-nine normal subjects served as controls. We performed pattern reversal visual stimulation and recorded the amplitude and latency of the cortical electric response at 100 ms (P100 wave). There were no differences in the mean P100 amplitude of TAO patients and normal subjects. The mean P100 latency in patients was 105.6 +/- 0.5 ms, significantly higher than that in normal subjects (102.0 +/- 0.5 ms; P < 0.00003). Latency in euthyroid patients did not differ from that in either hypo- or hyperthyroid patients. The VECP test was positive (latency, > or = 110.0 ms) in 21 (23.8%) TAO patients. In patients with proptosis greater than 21 mm, latency was 106.7 +/- 0.7 ms, significantly higher than that in patients with normal Hertel measurements (104.3 +/- 0.6 ms; P < 0.01). Latency was not increased in patients with acute inflammatory signs compared to those with inactive eye disease and in patients with altered extrinsic motility. In patients with an abnormal visual field study, the mean latency was 110.3 +/- 1.5 ms, significantly higher than that in patients with a normal visual field (104.7 +/- 0.4; by t test, P < 0.000003). In conclusion, we observed a prolongation of the latency of the evoked cortical response in patients with TAO without subjective visual complaints and without optic nerve compression. We believe that the study of VECP in TAO is complementary to the study of the visual field in identifying early optic nerve dysfunction in the absence of decreased visual acuity.

Increased serum interleukin-6 (IL-6) concentrations have been reported in patients with thyroid destructive processes. In the present study we measured IL-6 and soluble IL-6 receptor (sIL-6R) concentrations in the serum of normal subjects and patients with Graves' disease using a high sensitivity sandwich enzyme-linked immunoassay. We found increased serum IL-6 and sIL-6R concentrations (69.3 fmol/L, and 964 pmol/L, respectively) in 49 hyperthyroid patients with Graves' disease (GD) compared to those in controls [55.8 fmol/L (P = 0.019) and 772 pmol/L (P = 0.007), respectively]. In 31 newly diagnosed GD patients, serum concentrations of IL-6 and sIL-6R during the hyperthyroid phase were elevated, and after therapy with methimazole only, serum sIL-6R concentrations returned to normal (940 vs. 726 pmol/L; P < 0.001) but serum IL-6 did not. Serum sIL-6R concentrations (mean +/- 2 SD) were higher in GD patients with active inflammatory thyroid-associated ophthalmopathy than those in patients with inactive or absent thyroid-associated ophthalmopathy (P < 0.05). In conclusion, we have demonstrated activation of the IL-6 system in GD and, for the first time, have measured and found increased serum sIL-6R concentrations in hyperthyroid GD patients.

We have recently reported that many euthyroid patients with a history of Graves' disease treated years earlier with methimazole (MMI) have a positive iodide (500 micrograms)-perchlorate discharge test (I-ClO4 test), suggesting a permanent thyroid iodide organification defect. We now report the results of the I-ClO4 test in patients with hyperthyroid Graves' disease before beginning a 1-yr course of MMI therapy and 40 days after MMI was discontinued. Twenty-nine patients (25 women and 4 men; mean age, 38 +/- 1.7 yr) with their first episode of hyperthyroid Graves' disease were studied. Before MMI therapy, I-ClO4 tests were carried out, and serum T4, T3, and TSH were measured to confirm the diagnosis of hyperthyroidism. A positive I-ClO4 test is defined as more than 15% 131I discharged from the thyroid 1 h after the administration of 1 g KClO4. Patients were then treated with 20 mg MMI for the first 2 months and variable doses thereafter for the next 10 months to maintain euthyroidism. Serum T4, T3, and TSH were measured monthly. Forty days after MMI was discontinued, I-ClO4 tests were repeated, and serum T4, T3, and TSH were measured every 2 months thereafter. Before MMI treatment, the I-ClO4 test was positive in 20 of 29 patients (69%) and negative in 9. The favorable responses (normal serum T4 and T3 values) to MMI therapy were similar in both groups. We have thus far studied 16 patients after MMI was discontinued and 9 of 12 patients (75%) with a negative I-ClO4 test after MMI therapy, and 1 of 4 patients (25%) with a positive test remained in remission for a mean of 7 months. We conclude that the I-ClO4 test is frequently positive in patients with untreated hyperthyroid Graves' disease, suggesting either an inability to organify the increased iodide concentrated by the hyperfunctioning gland or the concomitant presence of Hashimoto's thyroiditis, which almost always is associated with a positive I-ClO4 test. The former hypothesis is more likely, because many patients with a positive I-ClO4 test before MMI therapy had a negative test after MMI was discontinued.

In view of the adverse effects of the administration of pharmacological quantities of iodine to euthyroid patients with a history of a wide variety of thyroid disorders, it has been suggested that iodine-containing medications and radioopaque dyes containing iodine should be avoided, if possible, in patients with underlying thyroid disease. We have now prospectively studied the effects of pharmacological doses of a saturated solution of potassium iodide (SSKI) on thyroid function in euthyroid patients with a previous history of hyperthyroid Graves' disease successfully treated with antithyroid drugs. Ten euthyroid women (mean age, 56 yr) who had hyperthyroid Graves' disease successfully treated with methimazole 36.4 +/- 4.7 months earlier were evaluated before, during, and after the administration of 10 drops SSKI daily for 90 days. The following thyroid function tests were obtained: serum T4, T3, TSH, TSH receptor antibody (TSH-RAb), and antithyroid peroxidase antibody (AbTPO) concentrations; TRH tests; and iodine perchlorate discharge tests. Serum T4, T3, basal and TRH-stimulated TSH, and TSH-RAb values were normal before SSKI administration, but serum AbTPO levels were markedly positive in 7 and iodine perchlorate discharge tests were positive in 4 of these 10 women. During SSKI administration, basal and TRH-stimulated serum TSH values increased above normal in 2 women with normal serum T4 and T3 concentrations; thyroid hormone values and TRH tests were normal in the other 8 patients and similar to values observed in 4 euthyroid women without a history of thyroid disease given SSKI. Serum AbTPO increased slightly, but significantly, during SSKI administration in the 7 women with positive values at baseline (P < 0.05). TSH-RAb remained undetectable. After SSKI withdrawal, the 10 women were reevaluated 60 and 120 days later. Two women developed a blunted TSH response to TRH, but normal serum T4 and T3 concentrations, and 2 women developed overt hyperthyroidism, with undetectable basal and TRH-stimulated serum TSH and elevated serum T4 and T3 concentrations, requiring methimazole therapy. All values in the remaining 6 women were similar to those present before SSKI administration. These results suggest that some euthyroid patients with a history of antithyroid drug therapy for Graves' disease may develop thyroid dysfunction during and after excess iodine administration. The development of subclinical hypothyroidism during SSKI administration was not clinically important, but the occurrence of overt hyperthyroidism after SSKI was discontinued did require antithyroid drug therapy. It is advisable, therefore, to avoid iodine-containing substances in euthyroid patients with a history of antithyroid drug therapy for Graves' disease.

Amiodarone-induced thyrotoxicosis (AIT) occurs most frequently in patients with underlying thyroid disease and is generally believed to be due to the iodine contamination of amiodarone and iodine released by the metabolism of the drug. We and others have suggested that the thyrotoxicosis may also be secondary to amiodarone-induced thyroiditis. To further determine the etiology of AIT, we administered large doses of iodides [10 drops saturated solution of potassium iodide (SSKI) daily] to 10 euthyroid patients long after an episode of AIT believed to be due at least in part to amiodarone-induced thyroiditis. Six of these 10 patients had an abnormal iodide-perchlorate discharge test before SSKI administration, indicating a subtle defect in the thyroidal organification of iodide. During SSKI administration, 6 patients developed marked iodine-induced basal and/or TRH-stimulated serum TSH elevations, 2 had suppressed basal and TRH-stimulated TSH values, and 2 had normal TSH responses compared to SSKI-treated euthyroid subjects with no history of amiodarone ingestion or thyroid disease. Serum T4 and T3 concentrations remained normal and unchanged during SSKI administration in both the AIT patients and control subjects. These results strongly suggest that excess iodine may not be the cause of the hyperthyroidism associated with amiodarone therapy, especially in those patients with probable amiodarone-induced thyroiditis. Furthermore, like patients with a previous history of subacute thyroiditis and postpartum thyroiditis, the present results suggest that some patients with a previous history of AIT may be at risk to develop hypothyroidism when given excess iodine.

Postpartum thyroiditis (PPT) is common and occurs in 1.7 to 16.7% of pregnant women, depending upon the study population. Most of these women develop transient hypothyroidism and thyroid function usually returns to normal. We have studied 11 euthyroid women with a previous history of PPT to determine the incidence of subtle defects in thyroid function measured by iodide-perchlorate (I-ClO4) discharge tests and TRH tests and to determine whether these women would develop iodide-induced hypothyroidism. Seven (64%) had positive I-ClO4 discharge tests and 5 (46%) had an abnormally high TSH response to TRH. Thyroid antimicrosomal and antithyroid peroxidase were positive in 8 women (73%) with a previous episode of PPT. The administration of pharmacological amounts of iodide (10 drops of saturated solution of potassium iodide daily) for 90 days to these 11 women resulted in elevated basal and TRH stimulated serum TSH concentrations in 8 (72.7%) compared to TSH values during iodide administration to women who had never been pregnant. Antimicrosomal and antithyroid peroxidase concentrations did not change during iodide administration. These findings strongly suggest that euthyroid women with a previous episode of PPT have permanent subtle defects in thyroid hormone synthesis and are inordinately prone to develop iodide-induced hypothyroidism, similar to findings previously reported in euthyroid subjects with Hashimoto's thyroiditis, with a previous episode of painful subacute thyroiditis, or previously treated with radioactive iodine or surgery for Graves' disease.

The effects of the administration of pharmacological quantities of iodide on thyroid function in 18 euthyroid patients with a previous history of painful subacute thyroiditis (SAT) were evaluated, and the results compared to those of iodide administration to 12 euthyroid patients with a previous history of thyroid surgery (TX) for benign nodular thyroid disease. After baseline thyroid function tests, saturated solution of potassium iodide (SSKI; 10 drops; 300 mg iodide) was administered daily for 120 days, and serum T4, T3, and TSH concentrations were assessed 15, 30, 60, 90, 120 days and 2-4 months after SSKI was discontinued. Iodide perchlorate discharge tests were carried out before SSKI administration, and TRH tests were performed on the last day of iodide administration. Two SAT subjects developed clinical evidence of hypothyroidism with markedly elevated serum TSH concentrations, and SSKI was discontinued on days 60 and 90, respectively. Thirteen of 18 SAT patients had at least 1 abnormal thyroid function test (iodide perchlorate discharge test, elevated serum TSH concentration, and abnormal TSH response to TRH) compared to 2 of 12 TX patients. These findings strongly suggest that euthyroid subjects with a previous history of SAT are prone to develop iodide-induced hypothyroidism, suggesting that subtle abnormalities in the thyroid organification of iodide and subsequent thyroid hormone synthesis persist years after the episode of SAT.