Reliability of Cortrosyn Test


Question

I did a CST on a young male, aged 16, because he had been given some compounded steroids by a "fibromyalgia clinic" because of diagnoses adrenal insufficiency. The early AM cortisol level was low at 2.1 ug/dl and the one hour was normal at 25.9 ug/dl. What is the significance of the low 8 AM value and do I need to do anything else? Clinically, he had hyperthyroidism due to compounded T3 from the same clinic and, of course, the T3 has been discontinued and further evaluation will be done in a few weeks after being off of the T3. Thanks for your help with this. Ann Ward, MD Taylorsville, GA

Response

Dear Dr. Ward, regardless of the basal value, a post cortrosyn test of greater than 20 mc per dL at 60 min suggests that you do not need to cover this patient with glucocorticoids. Single am measurements of cortisol can be misleading, granted that cortisol is secreted in a pulsatile fashion.Best regards!

GP Chrousos, MD