Background: Adrenal insufficiency is a common complication of pituitary surgery. We screen for hypoadrenalism with a day 4 morning cortisol. If < 400 nmol/l the patient is prescribed steroid replacement. Patients have a follow up short synacthen test at 6 weeks to assess the hypothalamic-pituitary-adrenal axis. We wanted to ensure the threshold of 400 nmol/l stopped patients with/or developing hypoadrenalism being discharged without glucocorticoid replacement. We also wanted to establish if patients who didnt develop long term hypoadrenalism although given steroid were appropriately picked up with the 6 week SST. Methods Retrospective study of 48 patients who had hypophysectomy (Cushings excluded). We correlated the result of day 4 cortisol with patients long term need for glucocorticoid replacement. We examined the efficacy of the 6 week SST for preventing further unnecessary glucocorticoid treatment.
Results: 31 of 48 patients required steroid replacement at least one year post op. All 31 of these patients had a day 4 cortisol less than 400 nmol/l. Therefore day 4 cortisol had 100% sensitivity. 28 of the 31 had day 4 cortisol less than 300 nmol/l. Highest day 4 value was 381 nmol/l. Of the 17 patients not needing long term steroids, 11 had a day 4 cortisol less than 400 nmol/l. Therefore the specificity of the test was low at 35.3%. Out of the 11 false positive cases, 11 out of 11 had adequate cortisol response to synacthen.
Conclusions: We conclude that a day 4 post hypophysectomy cortisol value <400 nmol/l is a very reliable screening test. The threshold of 400 does lead to low specificity, therefore high rate of unnecessary short term use of glucocorticoid post op. However, the 6 week follow up short synacthen test reliably clarifies this issue and prevents unnecessary long term steroid treatment.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.