Table 2.

Causes of malnutrition and sarcopenia in gastro-entero-pancreatic neuroendocrine neoplasms (GEP-NENs)

Cause	Mechanism Impacting Nutritional Status
Direct effect of the tumor	Tumors can impair absorption of nutrients leading to macro- and micronutrient deficiencies.
Surgical Procedures	Surgeries for GEP-NENs may disrupt normal digestive functioning, exacerbating malabsorption (mainly intestinal surgery) or maldigestion (mainly pancreatic surgery).
Hormonal Releases	Hormonal disturbances due to NENs can impact metabolic processes and nutrient utilization.
Specific Functioning NEN Syndromes	Syndromes like Carcinoid Syndrome (CS), due to the release of serotonin, Zollinger-Ellison syndrome (due to gastrin release), Verner-Morrison syndrome (vasoactive intestinal peptide (VIP) release), and somatostatinoma cause severe nutritional impairments due to diarrhea and increased nutrient losses. Glucagonoma also leads to systemic effects including severe malnutrition, diabetes mellitus, weight loss, depression, necrolytic migratory erythema (a type of dermatitis), deep vein thrombosis, and anemia.
Changes in the Ghrelin System	Alterations in the ghrelin hormone due to NENs are linked to changes in appetite and metabolism, affecting nutritional status.
Therapeutic Side Effects	Treatments like somatostatin analogs (octreotide and lanreotide) may induce exocrine pancreatic insufficiency, contributing to malnutrition in up to 20% of cases. Regular monitoring and tests for fecal elastase-1 are recommended to manage these effects.