The purpose of this monograph is to describe theoretical aspects of the interpretation of data obtained from experiments performed with labeled hormones. Quantitative endocrinologic studies involving the use of tracers include the determination of rates at which hormones are secreted by endocrine glands and are produced outside these glands by conversion of other secreted hor mones. Tracer experiments are also performed with the purpose of measuring rates of metabolic reactions. These measurements reveal the contribution of secreted hormones to the formation of circulating compounds and...