USMLE Guide: Adrenal Disorders

Introduction

Adrenal disorders refer to a group of conditions that affect the adrenal glands, which are located on top of the kidneys. These disorders can have significant implications on various physiological processes, including hormone production and regulation. Understanding adrenal disorders is crucial for medical professionals preparing for the USMLE exams. This guide aims to provide valuable information on adrenal disorders to help you succeed in your USMLE preparations.

Anatomy and Function of Adrenal Glands

The adrenal glands are composed of two distinct parts: the outer cortex and the inner medulla.

• The adrenal cortex is responsible for producing corticosteroid hormones, including cortisol, aldosterone, and androgens.
• The adrenal medulla produces catecholamines, such as adrenaline and noradrenaline.

Classification of Adrenal Disorders

Adrenal disorders can be broadly classified into three categories:

1. Adrenal Cortex Disorders:

   • Cushing's Syndrome - excessive production of cortisol.
   • Adrenocortical Insufficiency (Addison's Disease) - inadequate production of cortisol and aldosterone.
   • Hyperaldosteronism - excessive production of aldosterone.
   • Congenital Adrenal Hyperplasia - genetic disorder affecting adrenal steroid synthesis.

2. Adrenal Medulla Disorders:

   • Pheochromocytoma - adrenal medulla tumor leading to excessive catecholamine release.

3. Other Adrenal Disorders:

   • Adrenal Incidentaloma - an incidental finding of an adrenal mass.
   • Adrenal Insufficiency Secondary to Exogenous Glucocorticoid Use - inadequate adrenal function due to prolonged glucocorticoid therapy.

Clinical Presentation and Diagnosis

The clinical presentation of adrenal disorders can vary depending on the specific condition. However, certain common features can aid in diagnosis.

• Cushing's Syndrome:

  • Clinical Features: Weight gain, moon facies, buffalo hump, muscle weakness, easy bruising, and hypertension.
  • Diagnostic Tests: 24-hour urine cortisol, late-night salivary cortisol, and dexamethasone suppression test.

• Adrenocortical Insufficiency (Addison's Disease):

  • Clinical Features: Fatigue, weight loss, hyperpigmentation, hypotension, and salt craving.
  • Diagnostic Tests: Morning serum cortisol, ACTH stimulation test, and electrolyte levels.

• Hyperaldosteronism:

  • Clinical Features: Hypertension, hypokalemia, muscle weakness, and polyuria.
  • Diagnostic Tests: Plasma aldosterone-to-renin ratio, saline infusion test, and adrenal vein sampling.

• Pheochromocytoma:

  • Clinical Features: Paroxysmal hypertension, palpitations, headache, sweating, and anxiety.
  • Diagnostic Tests: 24-hour urine metanephrines, plasma free metanephrines, and imaging studies (CT/MRI).

Treatment and Management

The treatment and management of adrenal disorders depend on the specific condition diagnosed.

• Cushing's Syndrome:

  • Surgery to remove the source of excessive cortisol production.
  • Medications (e.g., ketoconazole, metyrapone) to control cortisol levels.
  • Radiation therapy in some cases.

• Adrenocortical Insufficiency (Addison's Disease):

  • Hormone replacement therapy with glucocorticoids (e.g., hydrocortisone, prednisone) and mineralocorticoids (e.g., fludrocortisone).

• Hyperaldosteronism:

  • Surgical removal of adrenal tumors (aldosterone-producing adenoma).
  • Medications (e.g., spironolactone, eplerenone) to control blood pressure and aldosterone levels.

• Pheochromocytoma:

  • Surgical removal of the tumor.
  • Preoperative alpha-adrenergic blockade (e.g., phenoxybenzamine) to prevent hypertensive crisis.

Conclusion

Adrenal disorders encompass a range of conditions affecting the adrenal glands and their hormone production. Understanding the anatomy, classification, clinical presentation, diagnosis, and treatment of adrenal disorders is essential for medical professionals preparing for the USMLE exams. This guide provides a comprehensive overview to aid in your exam preparation.