A New and Simplified Procedure for the Determination of Free Pregnanediol in Urine, and Its Evaluation*

THE estimation of urinary pregnanediol serves as a useful index of progesterone metabolism in the problems of pregnancy and menstruation. Since the isolation of pregnanediol by Marrian (1) and its later identification by Butenandt (2), two basic methods for its measurement have been devised. The first of these utilizes the pregnanediol glucuronidate complex and is expressed in terms of pregnanediol (3). The second determines free pregnanediol directly following the hydrolysis of the pregnanediol complex (4). Continuing studies have suggested that discrepancies exist between the quantity of pregnanediol excreted when measured by the two methods. It seems fairly well substantiated at the present time that in pregnancy the determination of the free pregnanediol yields significantly lower values (5). It would appear from present-day literature that methods utilizing the measurement of free pregnanediol have become the more popular of the two. In spite of many minor modifications, the results obtained with this method have been more or less uniform. Since pregnanediol is a relatively inert steroid, showing few and nonspecific color reactions, its determination in small quantities in the presence of larger quantities of other steroids is attended with some difficulties. Primary reliance must be placed on its isolation in as pure a state as possible, so that the quantitative determination does not include other steroids or chromogens.