Makindo Medical Notes

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

• Adrenal Adenoma – overview articles