SUMMARY
Various aspects of thyroid activity of a non-iodine-containing thyroid analogue, 3:5:3′-trichloro-d-thyronine (d-trichlor-thyronine = d-ClT3) have been studied and compared with those of 3:5:3′-triiodo-l-thyronine (l-triiodo-thyronine = l-T3).
As judged by the suppression of radio-iodine uptake in normal subjects, d-ClT3 is about six thousand times less active than l-T3 as an inhibitor of TSH production. Acute loading tests in hypothyroid patients showed that, judged by the effect on b.m.r., d-ClT3 is over 1600 times less potent than l-T3. Maintenance studies in hypothyroid patients showed that d-ClT3 at a dosage of 90 mg./day for 1 month achieved only partial restoration of the euthyroid state, and failed to maintain it in patients previously receiving other replacement therapy; this is 1500 times the minimum maintenance dose of l-T3. It was, however, found that the blood cholesterol levels fell to, or remained within, normal limits in all cases, suggesting that, like many other d-isomers, d-ClT3 has a relatively high hypocholesterolaemic potency.
There is no evidence that d-trichlor-thyronine possesses greater pituitary-suppressive than calorigenic potency; it is therefore unlikely to be of value in the treatment of Graves' disease.
Erratum to: Serum T3 Level and Duration of Minimum Maintenance Dose Therapy Predict Relapse in Methimazole-Treated Graves Disease