:La determinacion del cortisol plasmatico nocturno se ha propuesto como una alternativa en el diagnostico del sindrome de Cushing, principalmente para diferenciar entre pacientes con sindrome de Cushing y sujetos con estados de seudosindrome de Cushing.
:Se analizaron retrospectivamente las medidas de cortisol plasmatico a medianoche en 28 pacientes con sospecha clinica de sindrome de Cushing y elevacion de la excrecion de cortisol libre urinario (20 pacientes con sindrome de Cushing y 8 con seudosindrome de Cushing). No se realizaron estudios endocrinologicos el dia del ingreso. En los 2 dias posteriores se tomaron muestras para cortisol serico a las 8.00 y a las 24.00 h. Los resultados se compararon con otras pruebas diagnosticas realizadas simultaneamente (cortisol libre urinario y test de supresion con 1 mg de dexametasona).
El cortisol plasmatico a las 24.00 h fue el unico parametro que distinguio a todos los pacientes con sindrome de Cushing de aquellos con seudosindrome de Cushing. Su valor mas bajo entre los pacientes con sindrome de Cushing fue de 11,9 μg/dl, sin que se apreciaran diferencias entre los resultados obtenidos el segundo y el tercer dia de ingreso. En el grupo de pacientes con seudosindrome de Cushing, 3 casos presentaron un cortisol nocturno no suprimido durante el segundo dia de hospitalizacion (6,1–10,2 μg/dl), mientras que todas las determinaciones obtenidas 24 horas mas tarde proporcionaron valores menores de 5 μg/dl. Estos datos indican que el estudio del cortisol a medianoche puede requerir de un ingreso de al menos 48 h cuando se evalua a pacientes con seudosindrome de Cushing.
The determination of midnight plasma cortisol has been proposed as an alternative for the diagnosis of Cushing's syndrome, especially in order to differentiate patients with Cushing's syndrome from subjects with pseudo-Cushing's.
We retrospectively analysed the results of midnight cortisol measurements on 28 subjects with clinical suspicion of Cushing's syndrome and raised excretion of urinary free cortisol (20 patients with true Cushing's syndrome and 8 with pseudo-Cushing's states). No endocrine studies were carried out on the day of admission. Blood samples for serum cortisol assay were withdrawn at 8.00 and 24.00-h during the two following consecutive days. The results were compared to other laboratory investigations simultaneously performed (24 hours urinary free cortisol and overnight 1 mg dexamethasone suppression test).
Midnight cortisol was the only parameter that distinguished all patients with Cushing's syndrome from those with pseudo-Cushing's states. The lowest 24.00-h cortisol measured in a patient with Cushing's syndrome was 11.9 μg/dl and there were no differences between values obtained on either the second or the third day of hospital admission. In the pseudo-Cushing's group three cases showed unsuppressed midnight cortisol on the second day of hospitalisation (6.1–10.2 μg/dl), while cortisol concentrations were clearly blunted (< 5 (μg/dl) in all eight subjects when assessed 24 hours later. These data indicate that the measurement of midnight cortisol could require admission for at least 48 hours when patients with pseudo-Cushing syndrome are assessed.