Oral Presentation ESA-SRB Conference 2015

The role of a day 5 metyrapone test in assessing the HPA axis post pituitary surgery, a prospective trial (#190)

Katherine English 1 , Zara Weedon 1 , Jane Sorbello 1 , Warrick J Inder 1 2 , Anthony Russell 1 2 , Emma L Duncan 2 3 , Ross Cuneo 1
  1. Department of Diabetes and Endocrinology, Princess Alexandra Hospital, Brisbane, Queensland, Australia
  2. School of Medicine, University of Queensland, Brisbane, Queensland, Australia
  3. Department of Endocrinology and Diabetes, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia

Introduction: Pituitary surgery may result in new deficits in hypothalamic-pituitary-adrenal (HPA) axis function, but protocols for administering peri-operative glucocorticoids and assessing post-operative function differ widely. The objective of this prospective trial was to compare the performance of a Day 5 metyrapone test, postoperative morning cortisol levels, delayed metyrapone, short Synacthen test (SST) and insulin tolerance test (ITT) at 6-7 weeks post pituitary surgery as predictors of glucocorticoid replacement at 6 months.

Methods: The cohort consisted of 33 participants (16 women, 17 men),  who had undergone 30 trans-sphenoidal surgeries and 3 craniotomies - 24 non-functioning macroadenomas, 1 meningioma, 3 Rathke’s cysts, 4 GH-secreting and 1 GH and prolactin-secreting adenomas.

Morning cortisol (before 0900h) levels taken day 3 and 4 postoperatively (normal response: defined as >400nmol/L), metyrapone testing (30mg/kg) on day 5 and week 6 (normal response: 11 deoxycortisol >200nmol/L), SST week 6 and an ITT week 7 (normal response: cortisol >500nmol/L for both).  Post-operative glucocorticoid replacement was administered strictly per protocol. If morning cortisol was <400nmol/L and/or 11 deoxycortisol <200 nmol/L after metyrapone at day 5, hydrocortisone was given at <20mg daily until later testing.

Results: Mean tumour maximal diameter was 23mm (range 3mm-49mm). The prevalence of glucocorticoid requirement at 6 months was 55%.  The table illustrates sensitivity and specificity of each test as predictors of glucocorticoid replacement at 6 months.

Conclusions: These data suggest that both morning cortisol and day 5 metyrapone testing have good sensitivity in predicting glucocorticoid replacement at 6 months.  However, the sensitivities of morning cortisol, metyrapone testing at both 5 days and 6 weeks and STT were all lower than ITT. Interestingly in our study, the “gold standard” ITT had low specificity for predicting glucocorticoid replacement at 6 months. 

Table 1: HPA axis tests as predictors of glucocorticoid replacement at 6 months

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