A 30-year-old woman, presented 3 weeks postpartum, with episodes of sweating, dizziness and confusion, which occurred a few hours after eating and also on waking. At consultation she became vacant and lost consciousness. Her capillary blood glucose was found to be 1.2 mmol/l and she promptly responded to intravenous glucose administration. There was a history of several similar, but less severe episodes which required frequent feeding to avoid them. Her liver function and pituitary hormone profiles were normal. Four hours after admission for a supervised 72 hour fast, she developed neuroglycopaenic symptoms with plasma glucose of 1.9 mmol/l and inappropriately elevated levels of serum insulin 32 (normal; <5 mU/l), and c-peptide 409 (normal; 0.4 nmol/l). CT scan demonstrated a 2.5 cm tumour in the tail of the pancreas. Coeliac axis angiogram showed a single area of tumour blush in the tail of the pancreas, close to the spleen, corresponding to the lesion on CT scan. Serum gut hormones, calcium and parathyroid hormone (PTH) levels were normal and MEN-1 gene was not detected on genetic testing. She underwent a spleen-preserving distal pancreatectomy, with histopathology confirming 2 encapsulated islet cell tumours with positive immunostaining for insulin. She has remained euglycaemic following surgery.
Most cases of insulinoma associated with pregnancy have presented in the first trimester. Only a single case of post-partum insulinoma has been reported previously, which presented a few hours after delivery. Our case is unusual in presenting a few weeks post-partum. Later pregnancy is known to be an insulin resistance state. This may be due to placental counter-regulatory hormones like human placental lactogen, oestrogen, progesterone, and increase in free cortisol levels. These factors may have contributed to masking disease progression in later stages of pregnancy and patient presenting post-partum.