SFEBES2025 Poster Presentations Neuroendocrinology and Pituitary (48 abstracts)
Proinsulin secreting neuroendocrine tumour: diagnostic challenge
Khaled Ahmed 1 , David Bawden 1 , Hameed Rafiee 1 , Vidya Srinivas 1 , Mike Sampson 1 , Allison Chipchase 1 , Richard Kay 2 , David Halsall 2 , Robert Semple 3 & Khin Swe Myint 1,4
1Norfolk and Norwich University Hospital, Norwich, United Kingdom; 2Cambridge University Hospital, Cambridge, United Kingdom; 3University of Edinburgh, Edinburgh, United Kingdom; 4School of Medicine, University East Anglia, Norwich, United Kingdom
Background: Proinsulinoma is a rare neuroendocrine tumour (NET). Diagnosis is frequently challenging.
Presentation: A 79-year-old female presented with 2-year history of hypoglycaemia symptoms after morning exercise. A diagnosis of reactive hypoglycaemia was made after five-hour glucose tolerance testing (peak glucose 12.3mmol/l; nadir 2.7mmol/L at 210min). Complex carbohydrate supplements and acarbose were commenced but over 18 months symptoms progressed.
Further investigations: A 72h fast was carried out, soliciting spontaneous hypoglycaemia (Table). Concomitant insulin concentration was not consistent with insulin-driven hypoglycaemia, but C-peptide and proinsulin were elevated with a high proinsulin to insulin ratio. HbA1c was low (31mmol/l). Sulphonylurea screen, IGF2 and IGFBP3 were normal. Further fast again provoked hypoglycaemia, high insulin, C-peptide and proinsulin concentration (table) with a low fatty acid (0.8mmol/l) and capillary blood ketone concentration (0.6mmol/l), consistent with insulin-driven hypoglycaemia. Peptidomic analysis (mass spectrometry) identified Chromogranin B and neuroendocrine protein (7B2). Collectively, the biochemistry was most consistent with proinsulinoma.
Localisation studies: CT pancreas (Non-contrast due to contrast allergy), MRI, Tc99m HYNIC-TOC SPECT CT, and endoscopic ultrasound were inconclusive. DOTATATE PET-MR reported a potential lesion at the pancreatic head. All old scans were reviewed, revealing a 5mm hypervascular lesion in the pancreatic tail on post-contrast CT done 7 years ago. Revisiting DOTATATE PET-MR suggested a corresponding lesion. This was confirmed on repeat CT with contrast (with antihistamine cover).
Management: She required diazoxide therapy, followed by laparotomy and enucleation of the NET, with a resolution of hypoglycemia. Histology confirmed grade 1 well-differentiated NET.
| Hours into fast(h) | Plasma glucose (mmol/l) | Insulin (pmol/l) | C-Peptide (pmol/l) | Pro-insulin (0-7 pmol/l) | C-Peptide: Insulin | Proinsulin: Insulin | ||
| 14 Jun 23 | 20 | 2 | 5* <18# | 294 | 8.2 | 58.8 | 1.6 | |
| 14 Sep 23 | 15 | 1.9 | 17 | 569 | 13.3 | 42.7 | 0.78 | |
| *DiaSorin Liaison; # Mercodia | ||||||||
Conclusion: A strong clinical suspicion and persistent MDT approach was crucial for identification and management of a slowly evolving proinsulinoma.
Volume 109
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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