Endocrine · Year 2 · from Endocrine
Case 2: Adrenal Incidentaloma - Subclinical Cortisol Secretion
Patient Demographics
- Age: 58 years
- Sex: Female
- Occupation: Real estate agent
Chief Complaint
"A mass was found on my adrenal gland during a CT scan."
History of Present Illness
A 58-year-old woman had a CT scan of her abdomen performed for evaluation of kidney stones, which incidentally revealed a 2.5 cm left adrenal mass. She is asymptomatic with no classic features of Cushing syndrome. However, on detailed questioning, she reports mild weight gain over the past 2 years, poorly controlled type 2 diabetes despite multiple medications, and recently diagnosed hypertension. She bruises more easily than before. She has no symptoms of pheochromocytoma (headaches, palpitations, sweating episodes).
Physical Examination
- Vital Signs: BP 152/92 mmHg, HR 78 bpm
- General: Mildly overweight, no buffalo hump or moon facies
- Skin: A few bruises on arms, no striae, no hyperpigmentation
- Abdomen: No masses palpable
- Extremities: Mild proximal weakness if tested carefully
Workup
- Imaging:
- CT Abdomen: 2.5 cm left adrenal mass, 8 Hounsfield units (lipid-rich, benign appearance), homogeneous, well-circumscribed
- Washout characteristics: >50% (consistent with adenoma)
- Biochemical Evaluation:
- 1 mg overnight dexamethasone suppression test (DST): Cortisol 3.8 μg/dL (fails to suppress <1.8)
- Repeat DST: Cortisol 2.9 μg/dL (confirms non-suppression)
- ACTH: 4 pg/mL (suppressed, indicating autonomous cortisol)
- 24-hour urine free cortisol: 42 μg (normal <50)
- DHEA-S: Low-normal
- Late-night salivary cortisol: 0.12 μg/dL (borderline elevated)
- Plasma metanephrines: Normal
- Aldosterone/renin ratio: Normal
Diagnosis
Adrenal adenoma with autonomous cortisol secretion (previously "subclinical Cushing syndrome," now termed "mild autonomous cortisol secretion" - MACS)
Treatment Options
- Adrenalectomy (laparoscopic):
- Indicated given: diabetes poorly controlled, hypertension, autonomous cortisol secretion
- May improve metabolic parameters
- Will need peri-operative glucocorticoid coverage (suppressed contralateral adrenal)
- Taper steroids post-operatively as HPA axis recovers
- Conservative management (if surgery declined):
- Aggressive management of cardiometabolic risk factors
- Annual reassessment of hormonal status and imaging
- Consider bone density screening
- Post-surgical monitoring:
- Morning cortisol to assess adrenal recovery
- Taper hydrocortisone replacement over months
- Monitor glucose and blood pressure (may improve)
Clinical Pearl
Adrenal incidentalomas are found in ~5% of abdominal CT scans. All require biochemical evaluation for hormone excess: (1) 1 mg overnight DST for cortisol, (2) plasma or urine metanephrines for pheochromocytoma, and (3) aldosterone/renin ratio if hypertensive. MACS (mild autonomous cortisol secretion) is present in 5-30% of adrenal incidentalomas and is associated with increased cardiovascular risk, diabetes, and osteoporosis even without classic Cushing features. CT characteristics help distinguish benign from malignant lesions: <10 HU (lipid-rich adenoma), >50% washout (adenoma), while >4 cm size, irregular borders, or high density raise concern for carcinoma.
Clinical Image
CT scan showing a well-circumscribed, homogeneous left adrenal mass with low Hounsfield units consistent with a lipid-rich adrenal adenoma.
Image Source: Radiopaedia - "Adrenal adenoma" License: CC BY-NC-SA 3.0 URL: https://radiopaedia.org/cases/adrenal-adenoma-3