MON-179 Association Between Long-Term Prednisolone Induced Adrenal Insufficiency and Polymorphisms in the Glucocorticoid Receptor Gene

OBJECTIVE: Several biomarkers for glucocorticoid (GC) sensitivity have been proposed relevant for the inter-individual variation seen in treatment response and side effects to GC treatment. Four single nucleotide polymorphisms (SNPs) of the GC receptor (GR) gene have been associated with increased (Bcl1 and N363S) or decreased (9β and ER23/23EK) GC sensitivity. We investigated the influence of these proposed biomarkers for GC sensitivity on GC-induced adrenal insufficiency. SUBJECTS AND METHODS: We included 239 patients receiving long-term prednisolone treatment for rheumatoid arthritis (RA), polymyalgia rheumatica (PMR) / giant cell arteritis (GCA), or after renal transplantation (RTx). Four GR gene SNPs (Bcl1 rs41423247; 9β rs6198; N363S rs56149945; ER22/23EK rs6189 + rs6190) were sequenced by Sanger sequencing. Adrenal function was evaluated by a 250 µg corticotropin stimulation test. To compare allele frequencies with background population, two control groups were generated from two regional whole-genome databases. We downscaled each genome dataset to 239 individuals/group to balance statistical analysis. RESULTS: In total 239 patients were genotyped and 178 of these (RA n=103, PMR/GCA n=47, RTx n=28) treated with a median current dose of 5 mg prednisolone/day (interquartile range 5-7 mg) and a median treatment duration of 48 months (interquartile range 22-111 months) completed the corticotropin test. Seventy-three (41%, CI95%: 34-48%) patients had an insufficient response to the corticotropin test. Neither the risk of adrenal insufficiency, unstimulated nor stimulated P-cortisol levels were directly associated with any of the GR SNPs. However, for both insensitive SNPs 9β and ER23/23EK the effect of current prednisolone dose on stimulated P-cortisol was smaller (higher dose did not suppress the cortisol level as much) in carriers vs. non-carriers (p=0.035 and p=0.0075). The same sensitivity-associated tendency was seen for the N363S, but not the Bcl1 SNP. The Bcl1 SNP occurred more frequently in our cohort compared with control groups (63% vs. 40%, p<0.0001). The same trend was seen for the other sensitive but less frequent SNP N363S. The 9β SNP also occurred more frequently in our cohort (18% vs. 13%, p=0.029), but depending on regional sub cohorts in one control group. CONCLUSION: The GR SNPs did not directly associate to the risk of adrenal insufficiency, unstimulated nor stimulated cortisol levels, respectively. However, the effect of prednisolone dose on stimulated cortisol depended on the GR SNPs: Cortisol was less suppressed with higher current prednisolone dose in patients carrying the insensitive SNPs. The substantially higher frequency of the Bcl1 SNP is remarkable even with modest n=239. It questions whether there is an association between carrying the sensitive GR SNPs and inability to taper GC treatment ending up in this cohort of long-term treated patients.

Evaluation of Random Plasma Cortisol and the Low Dose Corticotropin Test as Indicators of Adrenal Secretory Capacity in Critically Ill Patients: A Prospective Study

It is unclear whether a random plasma cortisol measurement and the corticotropin (ACTH) test adequately reflect glucocorticoid secretory capacity in critical illness. This study aimed to determine whether these tests provide information representative of the 24 hour period. Plasma cortisol was measured hourly for 24 hours in 21 critically ill septic patients followed by a corticotropin test with 1 μg dose administered intravenously. Serum and urine were analysed for ACTH and free cortisol respectively. Marked hourly variability in plasma cortisol was evident (coefficient of variation 8–30%) with no demonstrable circadian rhythm. The individual mean plasma cortisol concentrations ranged from 286±59 nmol/l to 796± 83 nmol/l. The 24 hour mean plasma cortisol was strongly correlated with both random plasma cortisol (r2 0.9, P<0.0001) and the cortisol response to corticotropin (r2 0.72, P<0.001). Only nine percent of patients increased their plasma cortisol by 250 nmol/l after corticotropin (euadrenal response). However, 35% of non-responders had spontaneous hourly rises >250 nmol/l thus highlighting the limitations of a single point corticotropin test. Urinary free cortisol was elevated (865±937 nmol) in both corticotropin responders and non-responders suggesting elevated plasma free cortisol. No significant relationship was demonstrable between plasma cortisol and ACTH. We conclude that although random cortisol measurements and the low dose corticotropin tests reliably reflect the 24 hour mean cortisol in critical illness, they do not take into account the pulsatile nature of cortisol secretion. Consequently, there is the potential for erroneous conclusions about adrenal function based on a single measurement. We suggest that caution be exercised when drawing conclusions on the adequacy of adrenal function based on a single random plasma cortisol or the corticotropin test.