The evaluation of testicular Leydig cell function is of considerable clinical value in the investigation of gonadal problems in childhood, and adolescence. Testicular function was assessed in the patients in this thesis by the estimation of the basal plasma testosterone concentration, the basal daily urinary excretion of testosterone and the individual androgen metabolites and the changes in these parameters to administered HOG. This method therefore not only gives an index of testosterone production but also allows investigation of actual testosterone utilization by the patient. Following the addition of [1,2,6,7-3H] testosterone for recovery purposes, aliquots of plasma were made alkaline by the addition of sodium hydroxide and the testosterone extracted with diethyl ether. Purification of the extracted residues was effected by partition and thin layer chromatography. The dried residues were dissolved in dichloromethane and esterified with heptafluorobutyric anhydride for 30 minutes at room temperature. Following subsequent purification by thin layer chromatography, quantitation of testosterone-17-heptafluorobutyrate was made by electron capture detection on a Pye 104 gas liquid chromatograph. A correction was made for the recovery rate of radioactively labelled testosterone added initially to plasma samples. A near total hydrolysis of urinary conjugates of testosterone was effected by incubation with beta-glucuronidase (750 F.u. per ml urine) at 3
