Endocrine Abstracts

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Introduction: Insulinoma is a rare endocrine tumor originating from the beta cells of the pancreas, characterized by excessive insulin secretion and resultant hypoglycemia. While most insulinomas are benign and localized, approximately 10% progress to metastatic disease. The management of insulinoma often involves a multimodal approach. Surgical resection remains the first-line treatment, however, for metastatic cases, somatostatin analogs such as lanreotide and pasireotide are increasingly employed to control insulin secretion and tumor progression

Case: We present a case of a 58-year-old woman with MEN1 syndrome, diagnosed in 1994. The patient underwent repeated parathyroidectomy for parathyroid hyperplasia. In 1994, two-thirds of the pancreas were resected, and in 2012, an adenoma in the head of pancreas was enucleated due to the discovery of an insulinoma. The prolactinoma of the pituitary gland was managed with conservative treatment. In 2020, multiple liver lesions were found, along with recurring episodes of hypoglycemia. The presumed diagnosis was insulinoma metastases, but the lesions were not detected on the Octreoscan, which seemed to contradict the presumed diagnosis. Histological analysis of a biopsy from the dominant liver lesion confirmed a neuroendocrine tumor. Receptor testing revealed positivity for SSTR5 but negativity for SSTR2, explaining the negative Octreoscan findings. In 2022, microwave ablation was performed on the largest liver lesion. After that, the treatment with somatostatin analogues was initiated. The patient was first treated with lanreotide (pasireotide was not approved by insurance company). However, it did not adequately control the insulin secretion and episodes of hypoglycemia still occurred. Subsequently, therapy was switched to pasireotide, which effectively resolved the hypoglycemia. Pasireotide, with its high affinity for SSTR5, exerts potent antisecretory and antiproliferative effects, aligning well with the tumor’s receptor profile.

Conclusion: This case highlights the complexities of managing metastatic insulinoma in the context of MEN1 syndrome. It underscores the importance of individualized treatment strategies, including receptor profiling, to guide therapy selection. While lanreotide proved ineffective, the use of pasireotide successfully controlled the patient’s hypoglycemia, emphasizing the value of alternative somatostatin analogs for SSTR5-positive tumors. The multidisciplinary approach, including surgical interventions, receptor testing, and tailored medical therapy, was crucial in achieving symptom control and improving the patient’s quality of life.