[Nocturnal hypoglycemias and cortisol excretion in overnight urine]

In 20 juvenile diabetic inpatients the relationship between nocturnal hypoglycemia and overnight urinary cortisol excretion was studied. Cortisol was expressed as absolute quantity per kg body weight because the cortisol/creatinine ratio does not always yield reliable results in diabetic patients. Comparison between different patients yielded no significant difference between posthypoglycemic and non-posthypoglycemic cortisol values. Testing the difference between urinary cortisol excretion in posthypoglycemic and non-posthypoglycemic urine samples for every one of the patients intraindividually, however, a significant posthypoglycemic elevation was found. Posthypoglycemic cortisol response was irregular and variable not only in different patients, but also within the same patient. If a high excretion of cortisol is found in an overnight urine sample, it is very likely to be caused by nocturnal hypoglycemia. On the other hand it is impossible to exclude nocturnal hypoglycemia by normal urinary cortisol findings. Reactive hyperglycemia as described by Somogyi was seen only rarely in this study. It is concluded that even if a distortion by falsely high creatinine measurements in diabetics is ruled out, cortisol measurement in overnight urine samples cannot be used as easy routine method for the detection of nocturnal hypoglycemia.