SUN-021 - The Illusion of Remission in Cushing’s Disease : a Diagnostic Challenge in the Presence of Bipolar Disorder

Introduction
Cushing’s Disease (CD) is characterized by excessive production of adrenocorticotropic hormone (ACTH) by a pituitary adenoma. Spontaneous remission of CD is a rare phenomenon. Several possible mechanisms eg. tumor apoplexy, changing phenotype, senescence theory, cyclic CD have been proposed. We present a case of spontaneous remission of CD.
Case Presentation
A 26-years old woman patient with diagnoses of bipolar disorder admitted to endocrinology clinic with complaints of rapid weight gain, muscle weakness, menstrual irregularities and hirsutism. After cessation oral medications affecting dynamic tests for CD, a 1 mg dexamethasone suppression test (DST) yielded a result of 7.8. ACTH values were 18.4, 35.7, 43.8 pg/ml (7.2-63.3 ). Liddle test (2 days and 2 mg DST) yielded 10.07. 24-hour urinary cortisol levels were 346, 169 and 602 mcg/24 hours ( 3.5-45). Midnight plasma cortisol was 3.61. Midnight salivary cortisol couldn’t be measured due to unavailability of a kit. Contrast enhanced pituitary magnetic resonance imaging (MRI) revealed a 5 mm hypointense area in the right half of the pituitary gland, consistent wit a microadenoma. Due to diagnosis of bipolar disorder, the patient underwent a dexamethasone+ CRH test to rule out pseudo-Cushing’s. Fifteen minutes later after CRH administration, the cortisol level was measured at 5.9 mcg/dl and ruled out pseudo-Cushing’s. Because of the presence of overt Cushing’s symptoms the patient was scheduled for surgery, and an inferior petrosal sinüs sampling (IPSS) was performed. The IPSS showed a central/peripheral ACTH ratio of 2.7 (right) and 3.3 (left). Prolactin results from the IPSS confirmed the procedure was performed correctly . Pituitary MRI demonstrated a right sided lesion, whereas the IPSS showed clear left-sided lateralization suggesting a discrepancy between imaging and functional testing. Surgey was planned, but the patient refused and she gone under close observation. The patient’s cortisol response to 1mg DST was 0.75 mcg/dl and 24-hours urine cortisol was 100.3 mcg/24 hrs (20.9-292.3) two years after diagnosis. Cortisol responses to 1 mg DST were 1.61 mcg/dl after 3 years; 0.48 mc/dl and 24-hour urine cortisol 12 mcg/day ( 3.5-45) after four years. The last pituitary MRI showed no lesion in the pituitary gland. The diagnosis of the patient as a bipolar disorder was confirmed by a psychiatrist and she was in remission. For the past four years, the patient had no Cushing’s stigmas, except obesity .
Conclusion
Psychiatric comorbidities, such as bipolar disorder may obscure the clinical presentation and may delay the diagnosis of CD. However, patients with CD should be followed up carefully even if they undergo remission.

Key Words: Cushing’s disease, spontaneous remission, bipolar disorder

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