Endocrine Abstracts

Hydrocortisone day curves, Salivary cortisols, timed urinary free cortisols and 24 hour urine cortisols have been used to estimate hydrocortisone replacement in hypoadrenal patients.

We looked at 39 patients who had hydrocortisone day curve estimations in our hospital. 35 of those patients had simultaneous 24 hour urine free cortisol estimation. All hypothyroid patients were on adequate replacement dose of thyroxine.

The commonest clinical indication for day curve estimation was weight gain. The mean total dose of hydrocortisone replacement was 21.0 mg (10–30 mg). The mean age was 55.1 years, and weight was 80.3 kg. 29 patients had hypopituitarism and 10 patients had Addisons disease.

There was significant co-relation between 24 hour urine cortisol and mean blood cortisol level (r=0.461 P=0.005) as well as peak cortisol (r=.358 P=0.03). The calculated area under the curve (AUC) for cortisol profile correlated well with 24 hour urine free cortisol (r=0.443, P=0.008). The correlation was stronger in patients with hypopituitarism rather than in those with Addisons disease. The peak cortisol level was higher in those with an abnormal 24 hour urine free cortisol (917 vs 762 nmol/L P=0.05).

Conclusion: There is considerable controversy regarding the ideal test to assess hydrocortisone replacement in hypoadrenal patients. There is good correlation between 24 hour urine free cortisol and the mean, peak and area under curve(AUC) of an 8 point hydrocortisone day curve. Both tests measure different aspects of the pharmacokinetics of hydrocortisone replacement and are both useful in assessing optimum steroid replacement.