taking ghk cu Copper Peptide (GHK-Cu): Clinical Uses, Stability & Compounding Tips USA Copper Peptide GHK-Cu Powder,

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Inadequate secretion of intrinsic factor, resulting from lesions that destroy the gastric mucosa (which can be caused by ingestion of corrosives, extensive tumors, and conditions associated with gastric atrophy, such as multiple sclerosis, certain endocrine disorders, iron deficiency, and subtotal gastrectomy) Structural lesions leading to vitamin B 12 deficiency, including regional ileitis, ileal reactions, and malignancies Competition for vitamin B 12 by intestinal parasites or bacteria

(2019) ( Nature Publishing Group )

It's not always the case but it does come to mind