Endocrine Abstracts

The cortisol day curve has been advocated in the assessment of glucocorticoid replacement therapy in adrenal failure but remains controversial.
Objective: To determine the validity of this test within our practice.
Method: A retrospective analysis using endocrine laboratory dataset.
Results: 102 inpatient cortisol day curves from 76 patients were analysed. The serum cortisol was checked at 5 time points (pre and 1 hour post morning dose, before midday dose, pre and post evening dose). Mean age was 56 range 16-84years. 56 percent were male. There were 31 tests on a hydrocortisone 10/5/5milligrams dosing regimen and 25 tests on 20/10milligrams. The remainder were on varying regimen with a total dose of 10-50milligrams per day.
The pre-dose 1 cortisol concentration varied from undetectable (48percent) to 451nanomoles per litre. The post dose 1 level ranged from 123 to >1342nanomoles per litre (11 percent <500nanomoles per litre and 26 percent >900nanomoles per litre). Females had a significantly higher cortisol level 843+/-40 versus 738+/-29 (p=0.032) despite no significant difference in the dosage. There was no significant correlation between the dosage and the post dose 1 cortisol level. Pre dose 2 levels varied from 37-1086nanomoles per litre. 2 tests were <100nanomoles per litre and 15 percent of tests had values >600nanomoles per litre. Dose one correlates with the pre dose 2 level (r=0.378 p=<0.001). Pre dose 3 levels varied from 29-1178nanomoles per litre (27 percent <100nanomoles per litre and 5 percent >600nanomoles per litre). Dose 2 correlates with pre dose 3 level (r=0.342, p=0.012). 1 hour post dose 3 correlates with dose 3 (r=0.283, p=0.01)
Conclusion: The cortisol day curve is a useful tool and able to distinguish between varying doses of hydrocortisone. This test, although useful, must be interpreted with caution because of the great variability in the measured response.