Abstract
• A general slowing down of metabolic processes usually is associated with subnormal thyroid activity, but it can also be seen in cases where the thyroid is normally active as judged by its ability to take up radioactive iodine and by the levels of cholesterol and protein-bound iodine in the blood. The latter type of case is marked by differences in the effect of certain medicaments upon the patient. Eight patients are here described because their signs and symptoms of metabolic insufficiency were not relieved by protracted medication with desiccated thyroid preparations. Six of them improved subjectively and objectively when treated with 3, 5, 3′ L-triiodothyronine. The dosage had to be adjusted to the individual patient, but in general 50 mcg. per day was safe and effective. Since this drug not only is effective and rapid but also differs from desiccated thyroid in its site of action, it is valuable in the treatment of metabolic insufficiency.