A Case of Improvement of Insulinoma Symptoms in Pregnancy

Background: Insulinomas are rare tumors with an incidence of approximately 4 cases per million person per year. Only 39 cases of pancreatic neuroendocrine tumors have been reported in pregnancy. We report a case of pregnancy protecting the mother from manifesting the symptoms of insulinoma. Clinical Case: This case describes a 25-year old female who initially noticed symptoms of generalized weakness and oral tingling sensation in Fall 2018. She became pregnant in March 2019. She noticed an immediate reduction of the intensity of her symptoms during pregnancy. Her pregnancy was uneventful, and she delivered a healthy newborn in November 2019. Two months postpartum, she had worsening symptoms including syncopal episodes, confusion, difficulty ambulating and visual changes that improved with PO intake specifically carbohydrate intake. She was evaluated in March 2020 and labs showed the following: venous glucose 32 mg/dL, C-peptide 1.7 nmol/L, BOHB 0.4 mmol/L, Insulin 6.1 microU/ml, Proinsulin 25.8 pmol/L, IGF-2 354 ng/mL, negative insulin antibodies and negative oral hypoglycemic agent screen. TSH was unremarkable and AM cortisol was 16.1 mcg/dL. She was started on diazoxide twice a day. She underwent MRI of abdomen, which was negative followed by an EUS which was also negative. She had run out of her diazoxide and became severely symptomatic resulting in an ER visit where she was found to be hypoglycemic. Further evaluation was done with a Triple Phase spiral CT which showed a 1 cm arterial enhancing focal lesion within the pancreatic neck compatible with insulinoma. This was further evaluated with EUS FNA which confirmed the diagnosis of insulinoma on pathology. Her chromogranin A was 46.5 ng/mL. She is scheduled for surgical removal of the lesion. Conclusion: Pregnancy leads to an increased insulin resistance through hormonal changes with increased expression of placental growth hormone, human placental lactogen and the placental variant of corticotrophin‐releasing hormone (via ACTH and cortisol production), TNF-alpha and leptin. These changes that increase the insulin resistance act as a protective mechanism against the detrimental effects of an insulinoma. Pregnancy most likely also delayed the diagnosis of the insulinoma in this patient. Further research is warranted to evaluate the effects of an insulinoma on the mother and fetus. References: 1) Lowy AJ, Chisholm DJ. Insulinoma masked by pregnancy. Intern Med J. 2001 Mar;31(2):128-9. doi: 10.1046/j.1445-5994.2001.00017.x. PMID: 11480477.