Severely Fluctuating Blood Glucose Levels Associated with a Somatostatin-Producing Ovarian Neuroendocrine Tumor

Abstract

Somatostatin-producing tumors are a rare type of neuroendocrine tumor. Their effects on blood glucose levels have been variously reported, and detailed reports have been scarce. The aim of this study was to identify the reasons for the extraordinary blood glucose fluctuations in a case with no previous history of diabetes. A 68-yr-old nondiabetic woman with an ovarian tumor was suffering from hyper- and hypoglycemia. Based on the results of an oral glucose tolerance test and continuous glucose monitoring, we speculated that the fluctuating blood glucose level was accompanied not only by a low insulin level but also by low counter-regulatory hormones levels, and that those broad hormonal suppressions were caused by a high somatostatin level produced in the ovarian tumor. We performed an oophorectomy and assessed the pathology of the tumor and changes in the blood glucose profile as well as hormonal levels postoperatively. The blood glucose level was completely normalized after the oophorectomy. Insulin secretion was also normalized. Histological examination showed that the tumor comprised a mature cystic teratoma and a stromal carcinoid. Immunohistochemically, the stromal carcinoid component was positive for somatostatin. The somatostatin level was 8505 pmol/liter preoperatively, which dropped down to 71.5 pmol/liter postoperatively. We found two previous reports of somatostatin-producing ovarian neuroendocrine tumors. Somatostatin levels among cases of ovarian origin were much higher than those among cases of gastrointestinal origins, and cases of ovarian origin all experienced blood glucose fluctuations. Extremely high somatostatin levels and blood glucose fluctuations may be characteristics of somatostatin-producing ovarian neuroendocrine tumors.