Abstract
IntroductionThe diagnostic efficacy of biochemical and imaging modalities for investigating the causes of Cushing's syndrome are limited. We report a case demonstrating the limitations of these modalities, especially the inability of functional imaging to help localize the site of ectopic adrenocorticotropic hormone secretion.Case presentationA 37-year-old Arabian woman presented with 12 months of progressive Cushing's syndrome-like symptoms. Biochemical evaluation confirmed adrenocorticotropic hormone -dependent Cushing's syndrome. However, the anatomical site of her excess adrenocorticotropic hormone secretion was not clearly delineated by further investigations. Magnetic resonance imaging of our patient's pituitary gland failed to demonstrate the presence of an adenoma. Spiral computed tomography of her chest only revealed the presence of a non-specific 7 mm lesion in her left inferobasal lung segment. Functional imaging, including a positron emission tomography scan using 18-fluorodeoxyglucose and gallium-68-DOTA-D-Phe1-Tyr3-octreotide, also failed to show increased metabolic activity in the lung lesion or in her pituitary gland. Our patient was commenced on medical treatment with ketoconazole and metyrapone to control the clinical features associated with her excess cortisol secretion. Despite initial normalization of her urinary free cortisol excretion rate, levels began to rise eight months after commencement of medical treatment. Repeated imaging of her pituitary gland, chest and pelvis again failed to clearly localize a source of her excess adrenocorticotropic hormone secretion. The bronchial nodule was stable in size on serial imaging and repeatedly reported as having a nonspecific appearance of a small granuloma or lymph node. We re-explored the treatment options and endorsed our patient's favored choice of resection of the bronchial nodule, especially given that her symptoms of cortisol excess were difficult to control and refractory. Subsequently, our patient had the bronchial nodule resected. The histological appearance of the lesion was consistent with that of a carcinoid tumor and immunohistochemical analysis revealed that the tumor stained strongly positive for adrenocorticotropic hormone. Furthermore, removal of the lung lesion resulted in a normalization of our patient's 24-hour urinary free cortisol excretion rate and resolution of her symptoms and signs of hypercortisolemia.ConclusionThis case report demonstrates the complexities and challenges in diagnosing the causes of adrenocorticotropic hormone -dependent Cushing's syndrome. Functional imaging may not always localize the site of ectopic adrenocorticotropic hormone secretion.
Highlights
The diagnostic efficacy of biochemical and imaging modalities for investigating the causes of Cushing’s syndrome are limited
Magnetic resonance imaging (MRI) of her pituitary gland did not reveal the presence of an adenoma
Given the failure of biochemical or imaging techniques to localize the site of excess adrenocorticotropic hormone (ACTH) secretion, medical therapy was initiated with ketoconazole
Summary
The diagnostic efficacy of biochemical and imaging modalities for localizing the anatomical site of ectopic adrenocorticotropic hormone (ACTH) secretion are limited. Computed tomography (CT) of her chest, abdomen and pelvis only revealed a well circumscribed 7 mm left inferior basal lung segment lesion. Given the failure of biochemical or imaging techniques to localize the site of excess ACTH secretion, medical therapy was initiated with ketoconazole. Combination treatment with metyrapone was required after eight months due to rising 24-hour urinary free cortisol levels and progressive symptoms of weight gain, lethargy, depression and anxiety. Given the failure of medical therapy to control her symptoms, other potential treatment options were discussed with our patient These included progressing to bilateral adrenalectomy or resection of the lung lesion, which was the only possible anatomical site of ectopic ACTH secretion located so far. Her symptoms of Cushing’s syndrome slowly abated She achieved a normal 24-hour urinary free cortisol excretion off all treatment four months after surgery. Our patient remains well with no clinical or biochemical evidence of cortisol excess seven months after her surgery
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