INTERPRETATION OF THE LOWERED BASAL METABOLIC LEVEL*

Of the many metabolic studies developed to aid in the diagnosis of hypothyroidism, basal metabolism remains the most valuable. Even this test with all its simplicity is frequently difficult to interpret when it is found to be persistently low in patients lacking the physical signs of hypothyroidism. With the widespread use of the test in diagnostic procedures, it has become recognized that the accepted range of normal basal metabolic rates of ±10 per cent, established in the earlier years, did not meet all the requirements for accurate clinical interpretation. Likewise it has long been known that many persons with basal rates well below the level of —10 per cent fail to be benefited by thyroid medication. In certain well-defined physical states subnormal basal metabolism is the expected finding. Magnus-Levy (1) in 1906 first called attention to a low rate in marked inanition with the tendency to return toward normal with an improvement in nutrition. Hoskins (2) in a study of 300 cases of schizophrenia found a slight lowering of basal metabolism the rule. Furthermore, a lowered basal metabolic rate in mentally depressed states of appreciable degree is the common finding.