Cushing's Disease Management

Introduction to Treatment

• Cushing's disease treatment aims to normalize cortisol levels, with the Endocrine Society recommending a multi-faceted approach including surgery, medical therapy, and radiotherapy 1, 2
• The American College of Endocrinology and the Pediatric Endocrine Society also provide guidelines for the management of Cushing's disease, emphasizing the importance of individualized treatment plans 3, 2

Medical Therapy

• Ketoconazole is a first-line medical therapy for Cushing's disease, with an initial dose of 400-600 mg/day in 2-3 divided doses, increased to 800-1,200 mg/day until cortisol normalization, and a maintenance dose of 400-800 mg/day, as recommended by the Endocrine Society 1, 2
• Metyrapone is also a first-line medical therapy, with rapid cortisol reduction, but potential side effects include hirsutism, dizziness, and hypokalaemia 2
• Other medical therapies include osilodrostat, pasireotide, cabergoline, and mifepristone, each with varying efficacy and safety profiles, as summarized in the following table:

• Treatment adjustment should be considered if cortisol levels remain elevated after 2-3 months on maximum tolerated doses, as suggested by the Endocrine Society 1

Surgical Therapy

• Selective transsphenoidal adenomectomy is the first-line treatment of choice for patients with Cushing's disease caused by a pituitary microadenoma, with a strong recommendation and moderate-quality evidence, according to the Endocrine Society 2
• The endoscopic approach is preferred over microscopic transsphenoidal surgery, particularly in children and adolescents, as it potentially better preserves pituitary function, according to the American College of Endocrinology 3
• Surgery should be performed by experienced pituitary surgeons, defined as those performing at least 50 pituitary operations per year, as recommended by the American College of Endocrinology 3
• Strict fluid and electrolyte balance monitoring is essential peri-operatively and post-operatively, as emphasized by the American College of Endocrinology 3
• Complications of transsphenoidal surgery include changes in water metabolism and AVP regulation, resulting in diabetes insipidus in 26% and SIADH in 14% of patients, according to the American College of Endocrinology 3

Radiotherapy

• Radiotherapy is offered to patients with recurrent disease not amenable to curative surgery, with a strong recommendation and moderate-quality evidence, according to the Endocrine Society 2
• Options include focal external beam radiotherapy, stereotactic radiotherapy, fractionated proton beam radiotherapy, and gamma knife radiosurgery 2
• Approximately 80% of patients achieve biochemical remission during years after treatment with fractionated radiotherapy, which typically consists of 45 Gy in 25 fractions over 35 days 1
• A distance of at least 3-5 mm between tumor and optic chiasm and chiasm dose <8 Gy is recommended for stereotactic radiosurgery to limit damage 1

Monitoring and Follow-up

• The Endocrine Society recommends 6-monthly clinical examination, 24h UFC, electrolytes, and morning serum cortisol for at least 2 years, and annual clinical assessment thereafter for patients in remission 2
• Monitoring for pituitary hormone deficiencies, such as GH deficiency, is essential, as well as consideration for monitoring psychiatric and neurocognitive co-morbidities 2
• Efficacy monitoring should include 24-hour UFC, morning cortisol, and late-night salivary cortisol, as recommended by the Endocrine Society 1

Important Considerations

• Ketoconazole carries an FDA black box warning for hepatotoxicity, and regular liver function test (LFT) monitoring is essential to prevent severe liver damage, as emphasized by the Endocrine Society 1
• Drug interactions are numerous, and a careful review of the patient's medication list is essential to avoid adverse interactions, as recommended by the Endocrine Society 1
• Overtreatment causing adrenal insufficiency, undertreatment leading to persistent hypercortisolism, and misinterpreting insufficient disease control due to under-dosing as treatment resistance are potential pitfalls, as warned by the Endocrine Society 1
• Failing to monitor for drug-specific side effects and not recognizing drug-drug interactions, particularly with mifepristone, are also potential pitfalls, as recommended by the Endocrine Society 1
• Failing to recognize cyclical Cushing's syndrome is a potential pitfall, as highlighted by The Lancet Diabetes and Endocrinology 1