Suppression of the HPA axis and resulting adrenal insufficiency (AI) have been associated with exposure to exogenous GCs for almost as long as GCs have been in therapeutic use.

2 However, GCs are associated with a range of serious and non-serious side effects, 3 4 one of which is suppression of the hypothalamic–pituitary–adrenal (HPA) axis. In UK primary care, around half of patients with RA are prescribed oral GCs 1 and 13% of patients receive prescriptions of at least 3 months’ duration. Many patients with rheumatoid arthritis (RA) will be exposed to oral glucocorticoids (GCs) as part of their RA treatment. 7 NIHR Manchester Biomedical Research Centre, Manchester University NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK.6 Rheumatology Department, Salford Royal NHS Foundation Trust, Salford, UK.5 Faculty of Science, Division of Pharmacoepidemiology and Clinical Pharmacology, Utrecht University, Utrecht, The Netherlands.4 Health eResearch Centre, Centre for Health Informatics, School of Health Sciences, Manchester Academic Health Science Centre, The University of Manchester, Manchester, UK.3 Department of Clinical Biochemistry, Wythenshawe Hospital, Manchester University NHS Foundation Trust, Manchester, UK.

2 Division of Diabetes, Endocrinology and Gastroenterology, School of Medical Sciences, Manchester Academic Health Science Centre, The University of Manchester, Manchester, UK.

1 Arthritis Research UK Centre for Epidemiology, Centre for Musculoskeletal Research, School of Biological Sciences, Manchester Academic Health Science Centre, The University of Manchester, Manchester, UK.

Low cortisol