Central Diabetes Insipidus and Hypothalamic Type of Hypopituitarism Associated with Atypical Location of Rathke's Cleft Cyst

A 68-year-old woman was admitted to determine the pathogenesis of weight loss and polyuria. Physical findings on admission showed BMI of 20.9, blood pressure of 147/69 mmHg, and that she had ciliac, axillar and pubic hair loss. Laboratory findings showed that plasma adrenocorticotropic hormone (ACTH) was 4.6 pg/mL with serum cortisol of 1.2 μg/dL. Serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were markedly reduced. Serum growth hormone (GH) and insulin growth factor (IGF)-1 were 0.054 ng/mL and 25 ng/mL, respectively. Serum prolactin was as high as 85.6 ng/mL. The levels of all the pituitary hormones were elevated in response to a mixture of exogenous corticotrophin-releasing hormone (CRH), luteinizing hormone-releasing hormone (LH-RH), thyrotropin-releasing hormone (TRH), and growth hormone-releasing hormone (GRH). However, there was no response of ACTH and GH release to insulin-induced hypoglycemia and no response of LH and FSH release to clomiphene. Urine volume was more than 4,000 mL, with low urine osmolality of 134 mmol/kg. Plasma arginine vasopressin (AVP) was 0.8 pg/mL. There was no increase in urine osmolality and plasma AVP in response to 5% hypertonic saline load. Magnetic resonance imaging revealed Rathke's cleft cyst at the pituitary stalk level, but there was no abnormal finding in the hypothalamus. These findings indicate central diabetes insipidus and hypothalamic type of hypopituitarism, resulting from the atypical location of Rathke's cleft cyst.