A randomized trial of short-term treatment of Graves' disease with high-dose carbimazole plus thyroxine versus low-dose carbimazole.

OBJECTIVE: The optimal treatment regimen with thionamide drugs remains a matter for debate. We have investigated whether high doses of carbimazole, when compared with low doses, reduce relapse rates of Graves' disease. DESIGN: In an open label, randomized, prospective trial of treatment of Graves' disease we compared high doses of carbimazole (6 months of 100 mg carbimazole per day plus thyroxine) to low-dose carbimazole treatment (starting at 25 mg and titrating the carbimazole dose with the aim to maintain serum thyroid function test results within the normal reference range). PATIENTS: Thirty-seven patients with a first episode of Graves' disease were enrolled. MEASUREMENTS: During the 6 months of treatment we evaluated the rate of normalization of serum thyroid function tests, changes in serum thyroid auto-antibody levels and the rate of side-effects during treatment. After completion of the 6-month treatment course patients were observed for 2 years for evidence of relapse of Graves' disease. RESULTS: There were no differences between the two groups either in the rate of normalization of serum thyroid function tests or in serum thyroid auto-antibody levels during treatment. Of the 17 patients randomized to high-dose treatment seven suffered treatment side-effects, compared to only one of the 20 patients receiving low-dose treatment (P < 0.006). There was no significant difference in 2-year post-treatment remission rates on an intention-to-treat basis between the two treatment groups (18.7% vs. 5.9%, P = NS). However, for those patients who completed 6 months of treatment (high-dose group = 9, low-dose group = 16), multivariate survival analysis demonstrated a significantly longer median relapse-free interval (P < 0.04) in the high-dose group (27 weeks; 25th percentile: 9.6 weeks, 75th percentile: 75 weeks) versus the low-dose group (6 weeks; 25th percentile: 4.8 weeks, 75th percentile: 13.1 weeks). CONCLUSIONS: High-dose carbimazole treatment delays, but does not prevent, relapse from Graves' disease in those patients able to tolerate the treatment. However, it leads to more frequent side-effects than conventional dose treatment.

Treatment of hypothyroidism with once weekly thyroxine.

We compared daily T4 therapy with 7 times the normal daily dose administered once weekly in 12 hypothyroid subjects in a randomized cross-over trial. At the end of each treatment we measured serum free T4 (FT4), free T3 (FT3), rT3, and TSH levels and multiple markers of thyroid hormone effects at the tissue level repeatedly for 24 h. Compared with daily administration, the mean serum TSH before the administration of weekly T4 was higher (weekly, 6.61; daily, 3.92 microIU/mL; P < 0.0001), and the mean FT4 (weekly, 0.98; daily, 1.35 ng/dL; P < 0.01) and FT3 (weekly, 208, daily, 242 pg/dL; P < 0.01) were lower. A minimally elevated serum total cholesterol during weekly administration (weekly, 246.8; daily, 232.6 mg/dL; P < 0.03) was the only evidence of hypothyroidism at the tissue level. Compared with daily administration, the mean peak FT4 following weekly administration of T4 was significantly higher (weekly, 2.71; daily, 1.59 ng/dL; P < 0.0001), as was the mean peak FT3 level (weekly, 285; daily, 246 pg/dL; P < 0.01). None of the tissue markers of thyroid hormone effect changed compared to daily T4, and there was no evidence of treatment toxicity, including cardiac toxicity. During weekly T4 administration, autoregulatory mechanisms maintain near-euthyroidism. For complete biochemical euthyroidism a slightly larger dose than 7 times the normal daily dose may be required.

Mean platelet volume is increased in hyperthyroidism.

In 28 unselected patients with hyperthyroidism, platelet count, platelet hematocrit, mean platelet volume, and platelet distribution width were measured at the time of presentation and again when the patients were euthyroid. On return to the euthyroid state, there were highly significant falls in the mean values of the mean platelet volume (16% decline, P less than 0.001) and the platelet hematocrit (16% decline, P less than 0.001) and a slight but highly significant increase in the mean value of the platelet distribution width (2% increase, P less than 0.01). A decline in mean platelet volume was observed in 24 of 28 patients (86%); three patients showed no change. There was no significant change in the mean value of the platelet count. The observed effects of thyrotoxicosis on platelets appeared to be largely independent of the well-known effects on erythrocytes and white blood cells. An increase in mean platelet volume is a regular feature of hyperthyroidism that has not previously been described.