A Diagnostic Trap: Ectopic ACTH Cushing Syndrome With Incidental Pituitary Microadenoma
https://doi.org/10.15605/jafes.041.S1
- Author:
Khai Seong Khor
1
;
Ying Jie Tan
1
;
Lay Ang Lim
1
Author Information
1. Endocrinology Unit, Department of Medicine, Hospital Seberang Jaya
- Publication Type:Journal Article
- MeSH:
Cushing Syndrome;
Adrenocorticotropic Hormone
- From:
Journal of the ASEAN Federation of Endocrine Societies
2026;41(S1):25-
- CountryPhilippines
- Language:English
-
Abstract:
Introduction:Ectopic adrenocorticotropic hormone (ACTH)-dependent
Cushing syndrome is a rare but important cause of
hypercortisolism and can be difficult to diagnose,
particularly in the presence of incidental pituitary lesions.
Case:A 21-year-old patient presented with recurrent severe
hypokalemia, normotension, and rapid weight gain. The
hypokalemia was persistent, requiring multiple hospital
admissions and ongoing potassium supplementation.
Biochemical evaluation confirmed ACTH-dependent
Cushing syndrome with elevated ACTH (27.4 pmol/L),
elevated late-night salivary cortisol, and failure of
suppression on low-dose dexamethasone suppression
testing (cortisol 875 nmol/L). Pituitary magnetic resonance
imaging demonstrated a 0.5 × 0.3 cm microadenoma, raising
suspicion for a pituitary source. However, inferior petrosal
sinus sampling (IPSS) showed no central-to-peripheral
ACTH gradient, excluding Cushing disease. Computed
tomography of the thorax revealed a 0.6 cm right middle
lobe pulmonary nodule. Gallium-68 DOTATATE PET-CT
demonstrated increased somatostatin receptor uptake,
confirming the lesion as the likely ectopic ACTH source.
The lesion was not amenable to bronchoscopic resection,
and the patient was referred for cardiothoracic surgical
excision.
During the course of illness, the patient developed
resistant hypertension and worsening hypokalemia
requiring high-dose potassium supplementation and
multiple antihypertensive agents. Medical therapy with
ketoconazole and metyrapone was initiated for cortisol
control while awaiting definitive surgical resection.
Conclusion:This case highlights an aggressive and atypical presentation
of ectopic ACTH syndrome in a young patient, initially
presenting with isolated hypokalemia but rapidly
progressing to severe hypercortisolism. It underscores the
importance of early recognition, appropriate localization
with IPSS, and timely initiation of medical therapy to
control cortisol excess prior to definitive surgery.
- Full text:2026072813422207614EP_A013.pdf
