BACKGROUND: Epidural steroids injections are often used for the treatment of low back pain but their effects on the endocrine system have not been determined. Few studies have quantified the degree or duration of the suppression of the hypothalamic-pituitary-adrenal (HPA) axis in humans given epidural triamcinolone injection (ETI) for low back pain. The evaluation of the blood adrenocorticotropic hormone (ACTH) and cortisol was undertaken to determine the extent of suppression of the HPA axis in patients given ETI. METHODS: Lumbar epidural triamcinolone injections were performed on the painful lumbar intervertebral space with patients in the lateral decubitus position. The injection consisted of 40 mg of triamcinolone acetonide diluted in 10 mL of 1% lidocaine. Patients remained in the lateral position for 10 min after the procedure. Basal blood sampling was performed at 30 min before ETI and tested blood sampling was obtained at 7 days, 10 days, and 14 days after ETI. RESULTS: The blood cortisol level was significantly decreased at 7 days and 10 days but at 14 days was not significantly decreased and the blood ACTH level was not significantly decreased at 7 days, 10 days, and 14 days. CONCLUSIONS: Above results demonstrate that blood ACTH and cortisol level normalize 7 days and 14 days, respectively, after epidural triamcinolone 40 mg injection.