Discuss the hormonal regulation of carbohydrate, protein and fat metabolism.

1. 1 · Open in two lines. Hormones keep blood glucose and fuel supply steady between meals. Insulin builds stores in the fed state; glucagon and the stress hormones release them in fasting and stress.
2. 2 · Draw the see-saw. [Diagram: blood glucose in the centre; insulin lowers it; glucagon, epinephrine, cortisol, growth hormone and thyroid hormones raise it]
3. 3 · Insulin.
   • Carbohydrate: ↑ glucose uptake, glycogen synthesis, glycolysis; ↓ gluconeogenesis.
   • Protein: ↑ amino acid uptake and protein synthesis.
   • Fat: ↑ lipogenesis; ↓ lipolysis.
4. 4 · Glucagon and epinephrine.
   • Glucagon (liver): glycogenolysis, gluconeogenesis, lipolysis, ketogenesis.
   • Epinephrine: glycogenolysis in liver and muscle, lipolysis; quick stress response.
5. 5 · Cortisol, growth hormone and thyroid hormones.
   • Cortisol: gluconeogenesis, muscle protein breakdown.
   • Growth hormone: protein synthesis, lipolysis, anti-insulin effect on glucose.
   • Thyroid: raises BMR; more glucose use, lipolysis, lower cholesterol.
6. 6 · Significance. Insulin is anabolic; the rest are mostly catabolic. Failure of insulin action causes diabetes mellitus with hyperglycaemia, weight loss and ketosis.
7. 7 · Nutrition link. Low-GI foods and regular meals reduce insulin swings; iodine for thyroid hormones; zinc supports insulin storage.
8. 8 · Close in one line. Sum up the insulin–glucagon balance as the main switch between storing and releasing fuel.

Scoring tip: A four-column table (hormone against carbohydrate, protein and fat) is the fastest way to score here.