Abstract Disclosure: A. Lorin: None. M.C. Pranger: None. J. Park: None. C.A. Clutter: None. Background: Secondary adrenal insufficiency is well described in the literature with various offending agents implicated. Superior laryngeal nerve (SLN) glucocorticoid injections, however, have rarely been recorded as causal agents of secondary adrenal insufficiency. We present a case of a generally healthy man with secondary adrenal insufficiency after chronic administration ofsuperior laryngeal nerve glucocorticoid injections without other identifiable etiologies. Clinical Case: A 68-year-old man with no significant medical history presented to endocrinology clinic due to persistent nausea and severe fatigue. His initial labs were notable for morning cortisol of 1.66 mcg/dL (5-25) and an undetectable ACTH (<3.2 pg/mL, 10-60) suggestive of adrenal insufficiency. FSH/LH, testosterone, FT4, and IGF-1 were otherwise normal. On initial review of his medication history, the only glucocorticoid exposure appeared to be intranasal beclomethasone, with remote courses of oral prednisone. Further history revealed that the patient was receiving superior laryngeal nerve glucocorticoid injections for chronic cough every three weeks for over a year. The injection consisted of 1:1 mixture of 1 mL of triamcinolone acetonide 200 mg/5 mL and local anesthetic, which is equivalent to triamcinolone 40 mg or hydrocortisone 200 mg. Given the volume and chronicity of the glucocorticoid injections, the patient developed secondary adrenal insufficiency as above. Since the diagnosis, the patient discontinued SLN glucocorticoid injections and was placed on physiologic hydrocortisone replacement, with gradual recovery of his HPA axis. Conclusions: Sequelae of percutaneous glucocorticoid injection into the superior laryngeal nerve for treatment of chronic cough are not well documented in terms of their effects on the HPA axis. While an effective and increasingly common treatment for chronic cough, SLN glucocorticoid injection has the potential to cause suppression of the HPA axis and cause secondary adrenal insufficiency. Excess glucocorticoid appeared to solely inhibit ACTH production, as the other anterior pituitary hormones were not affected. Understanding consequences of glucocorticoid use in any formulation is important when considering such therapies, as these may alter normal HPA function with recurrent dosing. Recovery from a disrupted HPA axis may be achieved with the use of physiologic doses of hydrocortisone replacement in the case of secondary adrenal insufficiency. Presentation: 6/3/2024