Porter-Silber reaction [Curt C. Porter, American biochemist, b. 1914; Robert H. Silber, American biochemist, b. 1915] , a reaction, visible as a change in color to yellow, that indicates the amount of adrenal steroids (the 17-hydroxycorticosteroids) excreted per day in the urine. The test is used to evaluate adrenocortical function but is now largely supplanted by immunoassay techniques.
