Kinetics of cortisol metabolism and excretion. A hypothetic model based on the cumulative urinary radioactivity in eight multiple pituitary deficient patients.
A new model is proposed to study the kinetics of [3H]cortisol metabolism by using urinary data only. The model consists of 5 pools, in which changes of the fractions of dose are given by a system of 5 ordinary differential equations. After i.v. administration of [3H]cortisol to 8 multiple pituitary deficient (MPD) patients (group I) the urines from each patient were collected in 9-15 portions during the following 3 days. From the urinary data the rate constants of cortisol metabolism were calculated. A published set of urinary data from patients with a normal cortisol metabolism (group II) was used for comparison. The overall half-life of the label in the circulation was 30 min for both groups; the half-life of the label excretion by both groups was 6 h and the time of maximal activity in the main metabolizing pool was 1.8 h in group I and 1.5 h in group II. The 20% of normal cortisol production rate (CPR) in the 8 MPD patients amounted to 7.2 +/- 1.9 mumol/(m2*d). Therefore, the low CPR but normal rate constants, i.e. a normal metabolic clearance rate of cortisol, in the MPD patients suggest a sensitive adjustment of the cortisol response in the target organs.
Kraan
G P
GP
Department of Paediatrics, University of Groningen, The Netherlands.
Drayer
N M
NM
de Bruin
R
R
D000293:Adolescent; D000328:Adult; D003404:Creatinine / Q000652:urine; D005260:Female; D013006:Growth Hormone / Q000172:deficiency*; D006207:Half-Life; D006801:Humans; D006854:Hydrocortisone / Q000096:biosynthesis / Q000652:urine*; D007700:Kinetics; D008297:Male; D008954:Models, Biological; D014316:Tritium
D014316:Tritium; D013006:Growth Hormone; D003404:Creatinine; D006854:Hydrocortisone