Discussion
NICE guidelines indicate that long-term glucocorticoids should only be used for rheumatoid arthritis when all other disease-modifying treatment options have been offered and long-term complications have been fully discussed [39]. Short-term treatment may be considered for rapid control of inflammation in newly diagnosed rheumatoid arthritis or disease flares. For this patient, her arthritis is now controlled on methotrexate and withdrawal of treatment should be attempted.
When she tries to withdraw glucocorticoids, she develops symptoms that could be due to adrenal insufficiency or glucocorticoid withdrawal syndrome. The long duration of treatment and symptoms at a prednisolone dose below daily endogenous glucocorticoid secretion (~7.5 mg prednisolone equivalent) increase the likelihood that she has hypothalamic-pituitary-adrenal (HPA) axis suppression and adrenal insufficiency. HPA axis testing is therefore indicated to determine her long-term management.
A reasonable approach for this patient would be to ask her to repeat the wean to prednisolone 5mg. She should then undergo measurement of 9am cortisol at least 24 hours after her last dose of prednisolone, which can otherwise interfere with the cortisol assay. If this test is equivocal (9am cortisol 100-449nmol/L), further testing with a short synacthen test will be required. Differentiating between adrenal insufficiency, which requires adrenal replacement, and glucocorticoid withdrawal syndrome, which may resolve if treatment is tapered very slowly, is important to direct therapy.