Comparison of fluorometric corticoids and Porter-Silber 17-hydroxycorticoids during fasting

Simultaneous estimation of plasma cortisol levels was performed in 3 obese patients by a fluorometric technic and by the Porter-Silber reaction, during a control period, a 10 day fast and a refeeding period. During the fast a marked elevation in the values obtained by the Porter-Silber reaction was noted whereas the fluorometric measurements remained in the normal range. Evidence is presented that this elevation is due to an artifact probably caused by the elevated acetone bodies found during starvation.