Session: MON 306-326-Neoplasia of Endocrine Tissues: Case Reports
Poster Board MON-311
A 42 year-old man with high blood pressure and type 2 DM treated with metformin, had trans-sphenoidal surgery to resect a non-functional pituitary macroadenoma (4.1x3.4x2.5cm) with optic chiasm displacement after complaining of blurred vision. With the exception of a suppressed GH, all other pituitary hormones were normal. All follow-up to 6 months post-op were unremarkable. 9 months later he presented with altered mental status, blood glucose of 25mg/dL and undetectable insulin and c-peptide levels. Pituitary-adrenal and pituitary-thyroid axes were preserved, GH and IGF-1 levels (0.1 and 16 ng/mL) were below lower limits of normal (<10 and 52-328). He responded to initial treatment with intravenous dextrose but continued to have hypoglycemic episodes despite continuous D10 water infusion, diazoxide 200mg PO three times a day, and prednisone 40mg PO daily. During the course of hospitalization, diffuse metastatic disease was uncovered and a diagnosis of metastatic HCC was made. IGF-2 levels were elevated at 379 ng/dL (38-267 ng/dL). Due to impaired liver function in the setting of HCC, prednisone was switched to hydrocortisone with subsequent tapering and discontinuation of D10 water infusion and resolution of hypoglycemia.
Though NICTH was first recognized as a cause of fasting hypoglycemia in 1929 in a patient with HCC, it continues to be a poorly understood entity(1). Many studies have described this phenomenon as occurring most frequently in tumors of mesenchymal or epithelial origin, other case series of have found hepatic tumors to be the most common cause(2). The mechanism of hypoglycemia has been attributed to so-called "big" IGF-2, a more bioavailable form of IGF-2, which binds to IGF1R insulin receptors, inducing hypoglycemia by insulin-like activity. When the liver is involved, whether by primary tumor or metastases, impaired hepatic gluconeogenesis causes further detriment. Therapy with diazoxide-chlorthiazide and glucocorticoids has been shown to improve symptoms, in the latter case, it can also produce tumor shrinkage(1). While NICTH is rare, it should be considered in patients with malignant tumors suffering with hypoglycemic episodes or altered consciousness.
Nothing to Disclose: AT, AB, ASS, GB
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