Isolated adrenocorticotropic hormone deficiency manifested after COVID-19.

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 and long COVID can present with nonspecific symptoms resembling adrenal insufficiency. This similarity of symptoms means that adrenal insufficiency hidden among nonspecific manifestations of COVID-19 may pass underrecognized. We present the case of a 53-year-old Japanese man who developed isolated adrenocorticotrophic hormone (ACTH) deficiency (IAD) and acute adrenal insufficiency after COVID-19, thus mimicking prolonged symptoms of COVID-19. The patient developed fever, cough, and sore throat and was diagnosed with COVID-19. After anti-viral treatment, fever, loss of appetite, and general fatigue persisted, and hyponatremia was observed. Endocrinological testing on admission showed baseline concentrations of 3.5 μg/dL for cortisol and <1.5 pg/mL for ACTH. No abnormalities of other pituitary hormones were evident. Standard ACTH stimulation tests showed a decreased peak serum cortisol concentration and corticotropin-releasing hormone stimulation tests revealed no ACTH secretory response. Magnetic resonance imaging of the pituitary revealed no abnormalities. Adrenal insufficiency due to IAD was diagnosed based on the results of endocrinological testing. Intravenous and oral hydrocortisone improved symptoms and hyponatremia. The patient has experienced no recurrence of adrenal insufficiency under hydrocortisone treatment. COVID-19 can mimic adrenal insufficiency. IAD should be considered when nonspecific symptoms persist after treatment for COVID-19.