Blood Hormone Iodine and Iodide Reserve in Relation to Basal Metabolic Rate. ∗

Abstract

Five women diagnosed as having toxic adenoma were given 2 grains of desiccated thyroid per day with the results on the basal metabolic rate shown in Table I.

From this it is seen that the average basal metabolic rate was not appreciably increased. The same treatment was given to 11 patients with exophthalmic goiter and the results were as shown in Table II.

This shows that there is no increase in the average basal metabolic rate of exophthalmic goiter patients on feeding 2 grains of desiccated thyroid per day. This contained 0.2% of iodide; thus 2 grains contain 0.26 mg of iodine whereas iodized salt contains 0.02% iodine, and the average daily intake of 10 g would contain 1.5 mg or nearly 6 times as much iodine as is present in the desiccated thyroid. Such a dose of iodized salt is not considered sufficient to lower the basal metabolic rate as much as 2 grains of thyroid would be expected to raise it. Therefore it seems probable that in the patients being fed thyroid there was, on an average, a lessening of the secretion equal to the dosage. At any rate, some chemical means of determining thyroid hormone in the blood seemed desirable.

We define iodide reserve as the iodine extractable from blood with methanol followed by acetone, and hormone iodine as the non-ex-tractable iodine. The assumption that this non-extractable iodine is thyroid hormone iodine is supported by the fact that (statistically) the basal metabolic rate is directly dependent on the hormone iodine in the blood: since the micrograms of hormone iodine in 5 cc of blood = 0.01 × (the calories per square meter per hour —20). The remarkable statistical finding, in this region at least, on persons not receiving iodine medication, is that the iodide reserve is 0.01 × (60 — calories per square meter per hour).