Endocrine Abstracts

Background: Following pituitary surgery, dynamic testing with insulin tolerance (ITT) or glucagon stimulation testing (GST) is used to identify patients with secondary hypocortisolism who require glucocorticoids. High glucocorticoid replacement doses are associated with adverse effects, and the optimal replacement dose is unknown.

Aim: We aimed to assess the interpretation of dynamic testing post pituitary surgery in clinical practice and its relation with the hydrocortisone replacement doses used.

Methods: Retrospective review of all dynamic testing results post pituitary surgery between 2004 and 2014 in a tertiary centre, and of the medical notes.

Results: 101 patients fulfilled the inclusion criteria, out of which 61 (60.4%) were tested with an ITT and 40 (39.6%) with a GST. 27 patients were prescribed glucocorticoids following ITT testing, and 26 following GST. The decision regarding the hydrocortisone dose was made by the trainee or Consultant who had requested the test from clinic. Patients that were prescribed hydrocortisone 20 mg/day had significantly lower peak cortisol levels on dynamic testing compared to patients prescribed 10 mg/day (252±142 nmol/l vs 356±95 nmol/l, P<0.05) or emergency steroids only (484±45 nmol/l, P<0.005), but no different peak cortisol levels compared to patients prescribed 15 mg/day (313±149 nmol/l). Similarly, patients prescribed 10 mg/day or 15 mg/day had significantly lower dynamic testing peak cortisol compared to patients prescribed emergency hydrocortisone only (P<0.005 and <0.05 respectively). There was a trend to treat patients who had with radiotherapy with higher doses of hydrocortisone. Most patients continued the steroid dose recommended post dynamic testing and did not require dose changes in stable conditions with a follow-up of 4.4±3 years. On the day of dynamic testing, patients that failed an ITT or a GST had baseline cortisol of 205±112 nmol/l.

Conclusion: Patients diagnosed with hypocortisolism on dynamic testing post-pituitary surgery require variable dose or emergency only glucocorticoid replacement. The peak cortisol level on dynamic testing is useful when deciding the glucocorticoid replacement scheme.