Thyroid extracts are known for their effect on metabolism. Not only is the weight curve affected, but there is a greater excretion of water, salts and nitrogen, and growth and regeneration are promoted. This is most strikingly seen in the cretin or myxedematous patient. Associated with these metabolic changes is the elevation of the basal metabolic rate from a low to a normal level.
Before the advent of tests of basal metabolism, the effects of thyroid action were judged more or less clinically; that is, by improved mentality, increased irritability, decreased sluggishness and alterations in growth phenomena. Today, however, the association between studies of basal metabolism and of thyroid disease is so close that many consider scientific proof of thyroid disease lacking unless an abnormal basal metabolic rate has been demonstrated.1
As a corollary to this close association, the general impression has been that even in normal persons, exhibition