Endocrine Abstracts

JOINT1712

Introduction: Hypoglycemia in non-diabetic patients is a rare metabolic emergency that can arise from various causes. Non-islet cell tumor hypoglycemia is a rare but serious cause of hypoglycemia characterized by a paraneoplastic syndrome caused by a tumor that secretes high molecular weight IGF-2. Herein, we report a case of severe recurrent non-islet cell tumor hypoglycemia secondary to a large pulmonary tumor.

Observation: A 91-year-old woman was referred to the Endocrinology Department for hypoglycemia. Her medical history included hypertension, dyslipidemia, thyroid nodule, and a non-functional adrenal adenoma. In 2016, she presented with severe hypoglycemia and dyspnea. Laboratory investigations revealed low insulin and C-peptide levels during the hypoglycemic event. Although IGF1 and IGF2 levels were normal, the IGF2/IGF1 ratio was greater than 10, raising suspicion of a non-islet cell tumor secreting IGF2. A chest computed tomography (CT) scan showed a large right lung tumor measuring 150 mm. A PET-scan showed no significant hyper-metabolism in the lung mass. The patient was treated with corticosteroids and subsequently underwent a right pulmonary lobectomy. Anatomopathological examination revealed a benign fibrous tumor. Long-term follow-up was marked by the resolution of hypoglycemia. Eight years later, the patient presented with recurrent severe hypoglycemia, asthenia, and weight loss. On physical examination, she had a good state of hydration, a body weight of 44.2 kg, a height of 147 cm, a body mass index of 20.45 kg/m², a blood pressure of 128/59 mmHg, a heart rate of 69 beats per minute. Biological investigations showed a fasting blood glucose level of 0.36 g/l, an insulin level of less than 7 nmol/l, a C-peptide level of 0.03 nmol/l, an IGF1 level of 27 ng/ml, an IGF2 level of 485 ng/ml, and an IGF2/IGF1 ratio of 18. The CT scan revealed a necrotic and heterogeneous lung parenchymal mass measuring 111 mm in the right upper lobe. The patient was treated with corticosteroids and referred to the department of Thoracic Surgery.

Discussion: In this case, hypoglycemia was secondary to a fibrous pulmonary tumor that secretes IGF-2. IGF-2 interacts with insulin receptors, leading to the inhibition of gluconeogenesis, glycogenolysis, and ketogenesis. Generally, the diagnosis of non-islet cell tumor hypoglycemia is suggested when low insulin and C-peptide levels are observed during a hypoglycemic episode, along with a high IGF2/IGF1 ratio (> 3). Most fibrous tumors are benign. However, late tumor recurrence with aggressive features has been reported, even in the absence of prior evidence of malignancy.