Endocrine Abstracts

Dexamethasone is used to reduce cerebral oedema thus relieve symptoms of raised intracranial pressure. Long-term use causes suppression of the hypothalamic–pituitary–adrenal axis, which can lead to adrenal insufficiency. Undiagnosed, significant morbidity and mortality can occur from Addisonian crisis. The aim of this audit was to discover the relationship between adrenal insufficiency and long-term steroid use, in order to make recommendations for the use and withdrawal of dexamethasone in patients with solid brain tumours.

Patients who had a Short Synacthen test (SST) who also attended brain tumour clinic at the University Hospital Birmingham formed the basis of the study sample. This sample was divided into two groups depending on whether they passed the SST or failed it (i.e. have adrenal insufficiency). A retrospective evaluation of patient records was carried out and an area under the curve was calculated for each patient.

Results showed a significant difference between those who passed and failed their SST, but no differences within the groups. A significant negative correlation existed between baseline cortisol and both steroid duration and exposure, as well as between 30 min cortisol and duration, dose and exposure. Within the pass group subjects with no exposure were then excluded, statistically the group was still the same. A significant difference still existed between pass and fail groups. Results suggested a threshold point for failing the SST. Values at which failing the SST are most likely and significant are 2 mg mean dose, 150 day duration and 450 mg days exposure.

Therefore, steroid use above these threshold levels are most likely to cause adrenal insufficiency. With these findings, it can be recommended that such patients don’t need an SST; they are high risk of adrenal insufficiency, so should have hydrocortisone therapy to facilitate withdrawal of dexamethasone.