Diagnosis and Treatment > Signs and Symptoms
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Summary
Ectopic adrenocorticotropic hormone (ACTH) production leading to ectopic ACTH syndrome accounts for a small proportion of all Cushing’s syndrome (CS) cases. Thymic neuroendocrine tumors are rare neoplasms that may secrete ACTH leading to rapid development of hypercortisolism causing electrolyte and metabolic abnormalities, uncontrolled hypertension and an increased risk for opportunistic infections. We present a unique case of a patient who presented with a mediastinal mass, revealed to be an ACTH-secreting thymic neuroendocrine tumor (NET) causing ectopic CS. As the diagnosis of CS from ectopic ACTH syndrome (EAS) remains challenging, we emphasize the necessity for high clinical suspicion in the appropriate setting, concordance between biochemical, imaging and pathology findings, along with continued vigilant monitoring for recurrence after definitive treatment.
Learning points:
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Functional thymic neuroendocrine tumors are exceedingly rare.
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Ectopic Cushing’s syndrome secondary to thymic neuroendocrine tumors secreting ACTH present with features of hypercortisolism including electrolyte and metabolic abnormalities, uncontrolled hypertension and hyperglycemia, and opportunistic infections.
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The ability to undergo surgery and completeness of resection are the strongest prognostic factors for improved overall survival; however, the recurrence rate remains high.
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A high degree of initial clinical suspicion followed by vigilant monitoring is required for patients with this challenging disease.
Faculty of Medicine, Westmead Hospital, University of Sydney, Sydney, 2145, Australia
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Department of Endocrinology, Royal North Shore Hospital, St Leonards, 2065, Australia
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Faculty of Medicine, Westmead Hospital, University of Sydney, Sydney, 2145, Australia
St Vincent's Clinical School, University of New South Wales, Sydney, 2010, Australia
Diabetes and Transcription Factors Group, Garvan Institute of Medical Research (GIMR), Sydney, 2010, Australia
Department of Diabetes, Obesity and Endocrinology, The Westmead Institute for Medical Research, The University of Sydney, Sydney, 2045, Australia
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Summary
Ketoconazole was a first-line agent for suppressing steroidogenesis in Cushing's disease. It now has limited availability. Fluconazole, another azole antifungal, is an alternative, although its in vivo efficacy is unclear. A 61-year-old female presented with weight gain, abdominal striae and worsening depression. HbA1c increased to 76 mmol/mol despite increasing insulin. Investigations confirmed cortisol excess; afternoon serum cortisol was 552 nmol/l with an inappropriate ACTH of 9.3 pmol/l. In total, 24-h urinary free cortisol (UFC):creatinine ratio was 150 nmol/mmol with failure to suppress after 48 h of low-dose dexamethasone. Pituitary MRI revealed a 4-mm microadenoma. Inferior petrosal sinus sampling confirmed Cushing's disease. Transsphenoidal resection was performed and symptoms improved. However, disease recurred 6 months later with elevated 24-h UFC >2200 nmol/day. Metyrapone was commenced at 750 mg tds. Ketoconazole was later added at 400 mg daily, with dose reduction in metyrapone. When ketoconazole became unavailable, fluconazole 200 mg daily was substituted. Urine cortisol:creatinine ratio rose, and the dose was increased to 400 mg daily with normalisation of urine hormone levels. Serum cortisol and urine cortisol:creatinine ratios remain normal on this regimen at 6 months. In conclusion, to our knowledge, this is the first case demonstrating prolonged in vivo efficacy of fluconazole in combination with low-dose metyrapone for the treatment of Cushing's disease. Fluconazole has a more favourable toxicity profile, and we suggest that it is a potential alternative for medical management of Cushing's disease.
Learning points
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Surgery remains first line for the management of Cushing's disease with pharmacotherapy used where surgery is unsuccessful or there is persistence of cortisol excess.
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Ketoconazole has previously been used to treat cortisol excess through inhibition of CYP450 enzymes 11-β-hydroxylase and 17-α-hydroxylase, though its availability is limited in many countries.
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Fluconazole shares similar properties to ketoconazole, although it has less associated toxicity.
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Fluconazole represents a suitable alternative for the medical management of Cushing's disease and proved an effective addition to metyrapone in the management of this case.
