Steroid Secretion by the Human Testis

Abstract

To prove the secretion of a steroid, one must show that the venous effluent from the gland has a higher concentration of the steroid than has peripheral blood. This rigorous criterion is necessary since there is conversion among steroids in peripheral tissues as well as secretion by the adrenal cortex and gonads. There are, of course, important inferences that can be obtained about secretion without sampling the venous effluent by devising appropri ate experimental conditions both in vitro and in vivo. For example, the failure to demonstrate 11 ß-hydroxylation in the normal testis and ovary under any conditions almost surely places the origin of the 11ß -hydroxysteroids in the adrenal cortex. Suppression of adrenal cortical function in men does not alter plasma testosterone levels; thus testosterone must either be secreted by the testis or be a product of peripheral metabolism of another steroid secreted by the testis. This sort of inference has been made extensively and has been confirmed on many occasions. It should be clear however that the demonstration that a particular steroid is synthesized in vitro or in vivo from a radioactive precursor gives no information about secretion. One further caution is necessary; there are differences in the testicular secretory patterns among species so that extrapolation to man may not be warranted.