STUDIES ON THYROID: I. THE RELATION OF IODINE 
TO THE PHYSIOLOGICAL ACTIVITY OF 
THYROID PREPARATIONS. 
By Reid Hunt, 
Chief, Division of Pharmacology, Hygienic Laboratory, U. S. Public Health and Marine- 
Hospital Service, 
and 
Atherton Seidell, 
Chemist, Division of Pharmacology , Hygienic Laboratory, U. S. Public Health and Marine- 
Hospital Service. 
INTRODUCTION. 
Thyroid is a unique drug and occupies a place in therapeutics which 
can not be filled, even imperfectly, by any other known therapeutic 
agent. Its use was the first practical application of the doctrine of 
internal secretion and it still remains the most striking example of 
the conscious utilization, for therapeutic purposes, of an “ hormone.” 
Although much lias been learned in recent years in regard to the 
function of the thyroid as a. glandular organ and also as to the effects 
of the administration of thyroid preparations upon the organism, both 
in health and in disease, little progress has been made in the study 
of thyroid as a drug. The “ active principle ” of the gland is unknown, 
and there are no generally accepted means, aside from actual clinical 
tests, of determining the relative value of different thyroid prepara- 
tions. 
A very important advance in our knowledge of thyroid as a drug 
was made when Baumann 0 discovered in 1895 that the gland usually 
contains iodine. Since that time the chief interest in the chemistry 
of the thyroid has centered around this iodine, but the opinions as to 
the physiological significance of the latter are as far apart to-day as 
they were twelve or thirteen years ago. 
The question of the relation of the iodine to the physiological activ- 
ity of thyroid is from the pharmacological standpoint the most 
important problem connected with this drug; this is the subject of 
the present bulletin. 
a E. Baumann, Ztschr. f. physiol, chem., Strassb., 1895-96, 21, p. 319. 
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