Chapter 14 Exercises

Items marked † have worked solutions in the answers appendix. Everything else is for your own reasoning, your study group, or your instructor.

A reminder on the ground rules that apply to every item here: nothing in this chapter or these exercises constitutes dosing guidance, a protocol, or medical advice. Several items ask you to evaluate claims, marketing language, or a hypothetical patient's reasoning. None of them ask you to recommend a course of treatment, and an answer that supplies one has answered a different question.

Section A — Recall

A1. † Name the hypothalamic hormone that stimulates pituitary growth hormone release and the one that inhibits it. Say which is the accelerator and which is the brake, and state one reason it matters that the axis has both.

A2. What is IGF-1, roughly how long is it, where is most circulating IGF-1 produced, and what does it do to pituitary growth hormone release?

A3. Explain in two sentences why a single random blood growth hormone measurement is nearly uninterpretable.

A4. Name three effects of growth hormone that are direct and two that are mediated by IGF-1.

A5. Growth hormone is described as a counter-regulatory hormone. What does that mean, and what does it predict about blood glucose?

A6. State the Rudman finding in the exact form this book uses, including its final sentence.

A7. What is somatopause? Give the approximate rate of decline commonly cited and state the age after which it is usually described as beginning.

A8. Before recombinant production, what was the only source of human growth hormone, what disease was transmitted through some preparations, and in what year was distribution halted?

A9. † Write out this chapter's two ratings in full, each with its population and its endpoint.

Section B — Applied

B1. A 62-year-old man has an IGF-1 result at the low end of the reference range for his age. He has no history of pituitary disease, head injury, or cranial radiation. Using §14.3, explain why this result on its own does not establish adult growth hormone deficiency, and describe what a diagnostic workup would involve that a single result does not.

B2. † A user of exogenous growth hormone has bloodwork showing that his own pituitary growth hormone output has fallen. He concludes the drug has damaged his pituitary. Using the feedback loop in §14.1 and Chapter 3's account of feedback, explain what is actually happening and whether the observation is evidence of harm.

B3. A trial reports that participants receiving growth hormone gained lean mass and lost fat mass over 24 weeks, with no significant difference in grip strength or six-minute walk distance. Identify the surrogate endpoints and the outcome endpoints, and write one sentence describing what this trial supports and one describing what it does not.

B4. † Apply Chapter 5's replacement-versus-override distinction to three cases: (a) a 9-year-old with congenital growth hormone deficiency; (b) a 45-year-old who had a pituitary adenoma resected; (c) a healthy 58-year-old with an age-appropriate IGF-1. For each, say which frame applies and what that predicts about durability of benefit.

B5. Growth hormone and IGF-1 do not always push glucose in the same direction. Explain why, and say what that implies about describing the axis as "one dial."

B6. Using only §14.1, explain why a peptide that lifts the somatostatin brake and a peptide that presses the GHRH accelerator are different kinds of intervention, even if both raise measured growth hormone.

B7. † A systematic review of growth hormone in healthy older adults finds body composition changes but no convincing improvement in strength or function, plus more edema, arthralgia, and glucose impairment in treated participants. Write two sentences: one stating what this supports, and one stating what it does not — being careful not to convert "no evidence of effect" into "evidence of no effect."

Section C — Explain This to a Friend

Each item asks for a short, plain-language explanation. No jargon you have not defined in the same breath. Length limits are part of the exercise.

C1. In three sentences, explain to someone with no science background why doctors measure IGF-1 instead of growth hormone.

C2. In four sentences, explain why growth hormone works extremely well for one group of people and is not supported for another — without making it sound like a contradiction.

C3. Your friend read that "growth hormone reverses aging — there's a famous New England Journal study." In five sentences or fewer, explain what that study actually found, without dismissing it and without endorsing the conclusion.

C4. Explain to a friend, in three sentences, what acromegaly tells us about taking growth hormone — and one thing it does not tell us.

C5. † A friend asks: "Is growth hormone safe?" Answer in four sentences in a way that would be fair to a person with documented deficiency, a person considering it for anti-aging, and a person who has already started.

Section D — Identify the Red Flags

Each item contains a passage of the kind you would actually encounter. Identify every distinct problem you can find, name the reasoning error where one applies, and — this is the hard half — say what in the passage is true.

D1. † "hGH is the master hormone. Every system in your body depends on it, and it drops 14% per decade starting in your thirties. Restoring your levels to where they were at 25 is not experimental — it's replacement therapy, the same as thyroid or testosterone."

D2. "A landmark NEJM study showed growth hormone reversed 10 to 20 years of aging in men over 60. Nothing else in medicine comes close."

D3. "Our program uses bioidentical hGH, so there are no synthetic chemicals and no side effects. It's the exact molecule your body already makes."

D4. † "There's zero evidence that growth hormone causes cancer. That's a myth pushed by people who want to keep this away from you."

D5. "IGF-1 is the anti-aging biomarker. Ours is the only clinic that targets an optimal IGF-1, not just a 'normal' one for your age."

D6. † "Growth hormone is a peptide, and peptides break down into amino acids, so worst case nothing happens."

Section E — Judgment

These have no single right answer. They ask you to reason in public and defend a position.

E1. The chapter says whether the age-related decline in growth hormone is pathology or normal physiology is genuinely contested and declines to resolve it. Build the strongest case you can for each side, using only material from this chapter. Then say what evidence would move you, and how much.

E2. † Growth hormone is approved for idiopathic short stature — children who are simply short, with no identified pathology. Argue both sides. What does this indication have in common with the anti-aging claim, and what makes it different?

E3. The ❌ rating names a trial that would change it: long, randomized, blinded, with functional and clinical endpoints. That trial has not been run. List the reasons you can think of — scientific, economic, regulatory, ethical — and say which you find most persuasive as an explanation.

E4. † A person with no deficiency tells you they have been using growth hormone for two years, feel better, and have visibly less body fat. They are not asking your permission; they are asking what they should be paying attention to. Write what you would say. It must be honest about the evidence, useful, and free of moralizing — and it must not contain a protocol.

E5. Chapter 5's fourth frozen rule forbids downgrading a rating because you dislike a compound's associations. Is that rule ever wrong? Make the strongest case against it, then defend it.

Section F — Evidence Dossier Extension

F1. Complete Field 9 (all four parts: common/expected, serious/monitored, unknown/open, supply-chain) for every peptide currently in your dossier, including the ones you rate ✅.

F2. † For one compound in your dossier, find at least one item you had listed as a documented effect that is actually only a mechanistic concern, and move it to 9c. If you cannot find one, write a paragraph explaining how you verified each item's source — that is the harder and more useful outcome.

F3. Add a fifth line to your Field 9 template: 9e — what monitoring would detect it. Fill it in for growth hormone using §14.7 and §14.9, then for two other compounds in your dossier. Note where you cannot fill it in, and what that tells you.

F4. Date-stamp every entry in your dossier. Then, for each, write one sentence naming the finding that would most change your view. If any entry has no such sentence, that entry is currently a belief rather than an assessment.