Pituicytoma and isolated ACTH deficiency

Excerpt

A 55-year-old man was seen in the emergency room for abdominal pain, nausea, and vomiting. He did not have mental status changes. Serum sodium concentration was 111 mEq/l. Initial work up was consistent with hypovolemic hyponatremia. Normal saline infusion over the following 36 h brought up his serum sodium level to 129 mEq/l. He reported a 4-month history of fatigue and weight loss (5 lbs) and intermittent nausea, vomiting, anorexia, diarrhea, and lightheadedness. He denied headaches or visual disturbances. His medical history was remarkable for decreased libido and erectile dysfunction for 4 years. He had used sildenafil intermittently. Physical examination showed a 5′ 10′′ tall, 143 lb, white pale man with normal body hair distribution and no gynecomastia. After correction of his fluid imbalance, repeat test results showed that his hyponatremia was dilutional. He was on no diuretics. TSH was normal. Morning cortisol was 1.7 μg/dl and ACTH 13 pg/ml (7–69). The high-dose ACTH stimulation test was abnormal (serum cortisol levels were 14.2 and 9.7 μg/dl at 30 and 60 min, respectively). Central adrenal insufficiency was diagnosed and hydrocortisone begun with subsequent normalization of all his symptoms and serum sodium concentration. MR imaging after gadolinium administration revealed a 2.0 by 1.5 by 1.3-cm homogeneously enhancing mass in the suprasellar cistern that was abutting the optic chiasm (Fig. 1). The mass was isointense on T1-weighted images (Fig. 2). The pituitary stalk was not apparent (Figs. 1, 2). Further pituitary function studies were within normal limits except for a slightly elevated prolactin concentration of 37.4 ng/ml (2.1–17.7). Neuro-opthalmologic evaluation revealed mild bitemporal hemianopsia. He underwent transphenoidal surgery and partial resection of a presumed non-secreting pituitary macroadenoma. Pathology report revealed a benign spindle cell neoplasm most consistent with pituicytoma, WHO grade 1. Pituicytomas are rare hypervascular tumors originated in the posterior pituitary and/or its stalk, composed of spindle cells and presumably derived from pituicytes (glial cells that sustain the axons of vasopressin and ocytocin-secreting hypothalamic neurons). Pituicytomas are considered low-grade astrocytomas and histologically benign [1]. Presenting symptoms are usually due to tumor mass effects. Local recurrence after subtotal excision is not uncommon. Approximately 31 cases have been reported in the literature [2, 3]. Isolated ACTH deficiency has not been previously described to be the initial manifestation. Although he had symptoms of hypogonadism, his testosterone level was within normal limits on two different occasions.

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