Related Subjects:
|Adrenal Physiology
|Addisons Disease
|Phaeochromocytoma
|Adrenal Adenomas
|Adrenal Cancer
|Cushing Syndrome
|Cushing Disease
|Congenital Adrenal hyperplasia
|Primary hyperaldosteronism (Conn's syndrome)
|ACTH
|McCune Albright syndrome
🟡 Adrenal adenomas are the most common benign adrenal neoplasm, found in up to 5% of patients undergoing CT imaging.
Most are incidentalomas, but some are hormonally active, producing cortisol, aldosterone, or sex steroids.
📍 About
- Adrenal adenomas may be non-functioning or secrete cortisol, aldosterone, or sex hormones.
- They may be unilateral, bilateral, or occur simultaneously with other adrenal pathologies.
- A small, homogenous adrenal nodule is most likely to represent an adenoma.
🧬 Aetiology & Pathogenesis
- Linked to mutations or activation of the cAMP-dependent pathway.
- Mutations described in: ACTH receptor (MC2R), PRKAR1A, and PDE11A.
- Hormone-producing adenomas arise from dysregulated steroidogenesis in adrenal cortical cells.
🩺 Clinical Features
- 🌱 Asymptomatic (majority – “adrenal incidentalomas”).
- 🌡️ Cortisol-producing → Cushing’s syndrome (weight gain, skin thinning, proximal myopathy).
- 💉 Aldosterone-producing → Primary hyperaldosteronism (hypertension, hypokalaemia, metabolic alkalosis).
- ⚧ Rare: virilisation or feminisation due to androgen/estrogen secretion.
🔬 Investigations
- 🧪 Hormonal testing:
- Urinary free cortisol (screen for Cushing’s).
- Plasma aldosterone/renin ratio (if hypertension + hypokalaemia).
- 🖥️ Imaging:
- CT Abdomen: adenomas typically <3 cm, homogeneous, lipid-rich.
- Unenhanced CT: Hounsfield Units (HU) <10 → lipid-rich adenoma (highly specific).
- Indeterminate nodules: consider MRI (chemical shift) or FDG PET (adenomas usually non-avid; FDG-avid lesions → suspect malignancy).
- 🩸 Adrenal vein sampling: if high cortisol and low ACTH (to lateralise source).
- 📉 U&E: hypokalaemia in aldosterone excess.
🧫 Pathology
- Usually <5 cm and <50 g.
- 🌕 Aldosterone-secreting adenomas: often <2 cm, yellow-orange; may be multiple/bilateral.
- 💊 Spironolactone therapy → “spironolactone bodies” (eosinophilic globules in cells).
- ☀️ Glucocorticoid-secreting adenomas: larger, bright yellow/orange (lipid-rich).
- ⚫ Black adenomas: diffusely pigmented, often functional, usually associated with Cushing’s.
⚖️ Differentials
- Adrenal pseudocyst.
- Phaeochromocytoma (always exclude before adrenalectomy!).
- Adrenocortical carcinoma.
💊 Management
- 📋 Discuss at Endocrinology/Oncology MDT for risk stratification.
- 💊 Spironolactone for aldosterone-producing adenomas or hyperplasia (medical therapy).
- 🩺 Adrenalectomy → curative in functional adenomas; not effective for carcinoma.
- ⚠️ If carcinoma: consider mitotane (adrenolytic) ± radiotherapy.
- 🖥️ Follow-up imaging for incidentalomas if >1 cm, especially if indeterminate.
📚 Teaching Pearls
- Adrenal incidentalomas are found in ~5% of abdominal CTs — most are benign adenomas.
- Key imaging discriminator = unenhanced CT HU <10 → lipid-rich adenoma.
- Always exclude pheochromocytoma with plasma metanephrines before adrenal surgery.
- Spironolactone bodies are a pathognomonic histological clue in aldosterone-producing adenomas.
🔗 References
