Incidence of Adrenal Insufficiency and Cushing’s Syndrome After Long-Term Epidural Steroid Injections Over Six Months or Longer: A Preliminary Study

Purpose Endocrinological complications of an epidural steroid injection (ESI) are rare but dangerous. Nevertheless, despite the associated risks, repeated long-term ESIs are indispensable in some clinical situations. However, only a few reports to date have assessed the safety of this procedure. In this study, we evaluate the incidence of adrenal insufficiency (AI) and Cushing's syndrome after long-term ESIs. Methods This clinical observational study enrolled herniated nucleus pulposus or spinal stenosis patients who had received ESIs over a period of six months or longer. The adrenocorticotropic hormone (ACTH) stimulation test was performed to confirm AI and the late-night salivary cortisol (LNSC) test was performed to diagnose Cushing's syndrome. To evaluate the hypothalamus pituitary adrenal axis suppression, salivary cortisol (SC) levels were measured on days 0, 1, 7, 21, 28, 35, and 42. Results This study included 17 patients. Among these, two patients (11.8%) developed AI, but no cases of Cushing's syndrome were reported. There was no predictor for the development of AI. The SC levels tended to increase with time after an ESI (β = 0.003). The slope of the mixed effect model between the AI and non-AI groups showed a significant difference (p value = 0.015). However, the differences in mean SC levels at each time point between the two groups were not significant (adjusted p value = 0.053). Conclusion Long-term ESI use may be associated with AI development. An unexpected adrenal crisis due to AI could be life threatening. Therefore, regular monitoring of adrenal function in patients who have received long-term ESIs may be prudent.