Chapter 11 — Key Takeaways

Insulin

The core claims

Insulin was established without a randomized trial, because reversing a uniformly fatal condition in front of you leaves no alternative explanation standing. The general principle: the strength of evidence required scales with the plausibility of alternative explanations. For insulin in 1922 there were none. For essentially everything else in this book there are several — which is why Chapter 5 exists, and why insulin is an exception rather than a precedent.

51 amino acids, two chains (A = 21, B = 30), three disulfide bonds, ~5,800 Da. The bonds are the structure — which made recombinant production a folding problem and makes storage a real constraint.

The insulin receptor is a tyrosine kinase, not a GPCR. Insulin operates switches rather than amplifying a signal — which is why it has no glucose-dependence and therefore no built-in safety property.

Hypoglycemia is unavoidable in principle. Natural regulation has two levers — stop insulin and release glucagon. Injected insulin removes the first, leaving counter-regulation pushing against a fixed input. Every innovation since 1922 is an attempt to close the gap between delivered dose and actual need.

The asymmetry that shapes everything: too much insulin kills in an hour; too little kills over years. Glycemic targets are therefore a negotiated position, and the right position genuinely differs by person.

Type 1 is replacement; type 2 is overriding resistance. Which explains the chapter's central observation:

Insulin never stops working.

Fifty years of use, no tolerance. There is no intact system being overridden, no feedback loop measuring exogenous insulin, no set point being defended. The therapy is not fighting anything.

Compare Chapter 8: GLP-1 agonists override an intact appetite system, and weight returns on stopping. One rule (Ch 2 §2.8), opposite outcomes, and it predicts both.

1982: recombinant human insulin, the first recombinant drug. Decoupled supply from agriculture, removed animal-sequence immunogenicity, and — because you now build from a DNA sequence — opened the door to the analogs.

Each analog solves a timing problem: rapid-acting discourage hexamer formation; NPH uses protamine; glargine shifts the isoelectric point; detemir uses a fatty acid for albumin binding — the same strategy as semaglutide; degludec forms multihexamer chains.

Evidence ratings issued in this chapter

The pricing story, accurately

True: the 1923 patent was sold for a dollar; U.S. list prices rose far beyond manufacturing cost; people have rationed insulin and died doing so; U.S. prices exceed those elsewhere for identical products.

Complications the simple version omits:

• The 1923 patent covered the 1923 product. Modern analogs are separately developed and patented.
• List price is not net price. Rebates lower net prices for insurers and leave the uninsured paying near list.
• Biosimilar competition was slow for real regulatory reasons — demonstrating biological comparability is much harder than proving chemical identity.
• Prices have moved. Caps and competition have helped; the situation is better and unresolved.

The analytically decisive observation: type 1 diabetes is identical in every country. The rationing deaths are not. That locates the cause in health-system structure rather than in biology or manufacturing.

Key terms

type 1 diabetes · type 2 diabetes · insulin receptor · GLUT4 · hypoglycemia · hypoglycemia unawareness · diabetic ketoacidosis · basal insulin · bolus insulin · insulin analog · hexamer · isoelectric point · recombinant DNA · biosimilar · continuous glucose monitor · closed-loop system · smart insulin

What you can now evaluate

• ✅ when randomization is necessary and when a result speaks for itself
• ✅ why hypoglycemia is structural rather than a dosing failure
• ✅ whether any therapy is a replacement or an override — and what that predicts about discontinuation
• ✅ what each insulin analog was built to solve
• ✅ the pricing controversy, without defending anyone or overstating
• ❌ not yet: whether the same story is running again. Chapter 12.

The one-sentence version

Insulin is the most certainly effective drug in this book and the one whose hundred-year history says the least about pharmacology and the most about everything else — dosing, delivery, and who can afford it.

Next: Chapter 12 — cost, access, shortage, compounding, and the argument about what obesity is.