The somnolent metabolic rate (SMR) as an aid in the differential diagnosis of thyroid dysfunction.

DESPITE advances which have been made in our understanding of the essential nature of thyroid disease, the differential diagnosis of varying functional states often remains difficult. Much of the confusion has arisen because few objective methods have been developed to determine actual thyroid activity. In general, thorough and thoughtful clinical investigation remains a significant factor in arriving at a diagnosis. Nevertheless, the serum cholesterol, the basal metabolic rate, the serum protein-bound iodine, as well as radioactive iodine uptake studies all have been accepted as valuable adjuncts in determining the clinical diagnosis. In our hands the blood cholesterol has not shown sufficiently consistent change to be of any real help in indicating thyroid dysfunction. Although an elevated basal metabolic rate suggests overactivity of the thyroid gland and, more commonly, a lowered rate indicates diminished activity, it is recognized that the BMR may be affected by other factors in the presence of norma...