Endocrine Abstracts

Background: An insulinoma is a rare pancreatic neuroendocrine tumour. The incidence is about four cases per million individuals per year. The most common presentation of insulinoma is fasting hypoglycaemia with associated neuroglycopenic symptoms. They are commonly sporadic, usually small in size and majority are benign in nature. A few cases have been associated with genetic mutations.

Clinical Case: A 26-year-old man presented to the endocrine clinic with episodes of symptomatic hypoglycaemia for the last two years. His hypoglycaemic symptoms consisted of intermittent pins and needles sensations in his limbs, blurred vision and occasionally change in behaviour. These episodes were relieved by intake of sugary drinks or snacks. He was not known to have any family history to suggest MEN1 syndrome. He attended emergency department on one occasion with severe hypoglycaemia and a laboratory glucose of 0.6 mol/l. His cortisol, bone, thyroid and renal profile were all within normal values. His systemic examination was unremarkable. Further evaluation of his biochemistry showed low fasting glucose (1.9 mmol/l), raised insulin (78 pmol/l), raised c-peptide (530 pmol/l), low beta-hydroxybutyrate (64 micromol/l), in keeping with insulin-mediated hypoglycaemia. His IGF-2: IGF-I ratio was not in keeping with IGF-2 mediated hypoglycaemia. He had an initial CT triple phase scan done that showed a small hypervascular focus on the head of pancreas. A follow up MRI of his pancreas showed a 15 mm exophytic focus adjacent to the head of the pancreas which was consistent with a primitive neuroectodermal tumour (PNET). He had a DOTATATE PET CT which revealed increased DOTATATE avidity in the pancreatic head mass consistent with neuroendocrine tumour but no evidence of metastatic disease. EUS was suggestive of three lesions on the pancreatic head. He subsequently underwent surgical resection of the tumour (open Whipples’s procedure). Histopathology confirmed the diagnosis of a Grade 1 insulinoma, a 22 mm well differentiated neuroendocrine tumour, pT2pN0, Ki-67 <1%, MMR proficient with no nodal metastasis. He had good post-operative recovery with resolution of symptoms.

Conclusion: Insulinomas are rare neuroendocrine tumours. The treatment of choice is usually that of surgical excision of the tumour. After surgical treatment, the majority of patients are cured from the disease. For patients who are not candidates for surgical resection, medical treatment could be explored as an alternative option. Clinicians should have a high index of suspicion in patients who present with recurrent episodes of symptomatic hypoglycaemia particularly if they are resolved after eating.