Combination Drug Therapy for Treatment of Hyperthyroid Grave's Disease

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Abstract
The effects of three different treatment regimens on daily serum triiodothyronine (T3), thyroxine (T4) and 3,3′, 5′-triiodothyronine (rT3) were evaluated in 15 patients with hyperthyroid Graves' disease. Group I (n = 5) received propylthiouracil (PTU) 150 mg, and saturated solution of potassium iodide (SSKI) 3 drops, every 6 h for 7 days; Group II (n = 6) were given similar treatment as for Group I, plus dexamethasone (DEX), 2 mg every 6 h, from Day 5 through 8; Group III (n = 4) received PTU, SSKI and DEX as combined treatment from the first day. The mean serum T4 concentrations gradually fell in Groups I and II to about 75% of the basal value by Day 8. However, serum T3 concentrations fell abruptly in these same groups to 50% of the basal value after one day, and then slowly declined until Day 6; Group II patients showed a further significant decline (P < 0.01) in response to DEX administration. In Group III patients, the combined treatment with PTU, SSKI and DEX produced a lowering of serum T3 concentrations to 33% (range 29–36%) of the basal value after one day of therapy. This reduction was significantly greater than that observed in Group I (P < 0.005) or Group II (P < 0.02) patients. The measurement of serum rT3 concentrations revealed significant increases in mean values within one day in both Group I (P < 0.02 and Group II P (< 0.01) patients, then a return toward the basal values despite continued drug administration. Administration of DEX was associated with a further significant (P < 0.025) but transient elevation in mean rT3 concentration in Group II patients. In Group III, there was a marked elevation in serum rT3 values to 366% of the basal level (range 285–495%) at one day, which was significantly greater than that observed in either Groups I or II. These findings indicate that DEX and PTU have a similar and additive effect of inhibiting the conversion of T4 to T3, while transiently augmenting the conversion of T4 to rT3. Secondly, the combined administration of PTU, SSKI and DEX in thyrotoxic Graves' disease patients was capable of producing a reduction in serum T3 concentrations to the euthyroid range within 24 h, a finding which may be of clinical benefit in selected patients with severe hyperthyroidism.

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