Instructor Notes — Chapter 7
Teaching notes
What this chapter is actually for
Three things students must be able to do afterward:
- Explain glucose-dependence and use it to predict which drugs cause hypoglycemia and which do not. This single concept explains a large fraction of the class's clinical behavior.
- Name the four actions and say which one is load-bearing for a given claim. This is the habit that makes Chapters 8–13 legible, and it generalizes to any multi-action molecule.
- State honestly that the drug and the endogenous hormone may not be the same signal. This is the chapter's most sophisticated point and the one most likely to be lost.
The chapter is also the last in Part II with no drugs in it, and students will be impatient. Tell them at the start that three questions they came with — why the nausea, why no hypoglycemia, why the weight returns — are all answered here, and that the drug chapters make no sense without it.
Common misconceptions
"GLP-1 causes insulin release." It amplifies release that glucose is already driving. Students who miss this cannot explain why hypoglycemia is uncommon, and will get exercise 7.10 wrong in both halves.
"These drugs restore natural signaling." The chapter's most important correction, and it is subtle because the sentence sounds both accurate and generous. §7.6 and §7.7 dismantle it: different routes, different concentrations, different temporal pattern, and no established prior deficiency. Quiz Q22 is the item that tests it.
"The nausea is a side effect." It is one of the four intended actions overshooting. Reframing this changes how students think about the whole class — and it is genuinely useful clinically, because a patient who understands that the nausea and the benefit share a mechanism responds differently to it.
"GIP is the bad one." The straightforward story (blunted in diabetes, promotes fat storage) is the one most sources tell, and tirzepatide contradicts it. §7.5 is where students learn that a field can have a confident consensus that a drug then embarrasses.
"The incretin system explains obesity." §7.9 exists for this. A drug acting on a system is not evidence the system caused the disease — the CAST lesson, in a new setting. This misconception is common in students who have just been impressed by Part II's opening and it should be caught early.
The hardest point to teach
That endogenous GLP-1 and an injected agonist may be different signals.
Students find this counterintuitive because the molecule is described as an "analog" and the receptor is the same. The argument requires holding four facts at once: DPP-4 destroys most endogenous GLP-1 before it circulates; endogenous action is therefore probably substantially local and vagal; injected agonists produce sustained systemic exposure; and some brain regions have an incomplete blood-brain barrier.
What works: draw §7.7's three-routes diagram and ask which routes the endogenous hormone uses and which the drug uses. Students arrive at the answer themselves and it holds better.
Then ask the payoff question: if the drug produces weight loss that endogenous GLP-1 never produces, is that surprising? Once they see that the signals differ, the magnitude stops being mysterious — and the phrase "restores natural signaling" becomes visibly wrong rather than merely imprecise.
Demonstrations that work
The incretin experiment, drawn. Draw two glucose curves matched, then two insulin curves that are not. Ask what could account for the difference. Students propose things; eventually someone suggests the gut. Five minutes, and the whole chapter has a motivating question.
Glucose-dependence by contrast. Put three drugs on the board — insulin, a sulfonylurea, a GLP-1 agonist — and ask which cause hypoglycemia and why. The answer falls out of one property, and students remember it because it predicts something.
The four actions as a table students fill in. Give them the four tissues and have them predict the action at each. They get insulin and appetite quickly; glucagon and gastric emptying require thinking. Then ask which action produces the nausea, and which produces the weight loss. The realization that one action produces both a benefit and the main side effect is the useful moment.
Read a label's Clinical Pharmacology section. Project one from DailyMed. It states the mechanism in regulatory language — noticeably more careful than any marketing copy. Ask students to find what the label does not claim.
Timing
For a 75-minute session:
| Minutes | Content |
|---|---|
| 0–10 | §7.1 — the incretin experiment, drawn. Motivating question. |
| 10–18 | §7.2 — the L cell. Emphasize distal concentration; it pays off in CS2. |
| 18–32 | §7.3 — the four actions. Table exercise. |
| 32–44 | §7.4 — glucose-dependence. The three-drug contrast. |
| 44–54 | §7.5 — GIP and the paradox. Do not resolve it. |
| 54–62 | §7.6 — DPP-4 and the two-minute problem. |
| 62–72 | §7.7 — the three routes. The chapter's hardest and best section. |
| 72–75 | §7.9 — what it does not explain. Assign the deepened Field 3. |
If short on time, compress §7.5 and assign it. Do not compress §7.4 or §7.7.
Assessment notes
Discriminating items: 7.10, 7.13, 7.15, 7.21, 7.26.
7.26 (identify claims the routes-may-differ argument should make you cautious about) is the best summative item — it requires students to apply a mechanistic subtlety to a communication claim, which is what the whole book is training.
7.21 ("food noise" on the evidence ladder) is worth grading carefully. The correct answer holds two positions: the report is genuine, consistent, unprompted, and mechanistically plausible; and the evidence is currently of a kind Chapter 5 rates cautiously. Students who resolve it in either direction have lost the point.