Insulin & Diabetic Emergencies

Introduction

• Insulin — A 51-amino-acid two-chain (A 21 + B 30) polypeptide hormone of pancreatic islet β cells, joined by two disulfide bonds; the anchor drug of all type 1 diabetes and of advanced/decompensated type 2, and the only agent that reverses the acute hyperglycaemic emergencies.
• Biosynthesis — Preproinsulin → proinsulin → insulin + C-peptide (co-secreted equimolar); because C-peptide escapes hepatic first-pass (t½ ~30 min vs insulin ~5 min), peripheral C-peptide is the marker of endogenous β-cell secretion and separates endogenous from factitious hyperinsulinaemia.
• Unit & strength — 1 IU ≈ 34.7 µg crystalline insulin; most preparations are U-100 (100 U/mL); concentrated U-200/U-300/U-500 forms exist for insulin-resistant patients needing large volumes.
• Scope of emergencies — Three acute decompensations — diabetic ketoacidosis (DKA) and hyperosmolar hyperglycaemic state (HHS) from insulin lack, and hypoglycaemia as the iatrogenic mirror image from insulin/secretagogue excess. Oral antidiabetics & SGLT2 inhibitors are covered in the sibling LAQ "Newer Oral Antidiabetics & SGLT2 Inhibitors".