Skip to content

Human Physiology · Endocrine and reproduction

The Endocrine Pancreas and Glucose Control

Insulin and glucagon keep blood glucose within a narrow range despite meals, fasting and exercise. This page explains how they work, how muscle takes up glucose, what goes wrong in diabetes, and why exercise is one of the most powerful treatments and preventions.

11Sections
5Figures
4Tables
10Questions

Part 8 · Endocrine and Reproduction · Chapter 37 of 47

Learning objectives

By the end of this page you should be able to:

  • Describe the endocrine cells of the pancreas and their hormones.
  • Explain the feedback control of blood glucose by insulin and glucagon.
  • Explain how insulin and muscle contraction increase glucose uptake.
  • Distinguish type 1 and type 2 diabetes and interpret common tests.
  • Summarise evidence on lifestyle prevention and exercise treatment of diabetes.
  • Exercise patients with diabetes safely.

Why it matters

Diabetes is one of the commonest conditions in rehabilitation, particularly in India and South Asia. It affects wound healing, nerves, circulation, eyes, kidneys and heart, and it changes how patients respond to exercise.

Exercise is also a central treatment for type 2 diabetes. Physiotherapists who understand glucose control can prescribe it confidently and avoid hypoglycaemia.

The islets of Langerhans

CellHormoneMain action
Beta (most cells)InsulinLowers blood glucose; promotes storage of fuel and protein synthesis
AlphaGlucagonRaises blood glucose by liver glycogen breakdown and glucose production
DeltaSomatostatinRestrains insulin and glucagon release

Figure 1 · Two hormones keep glucose in range

Insulin and glucagon feedback control of blood glucose When blood glucose rises, beta cells release insulin, which drives glucose into muscle, fat and liver and lowers it. When glucose falls, alpha cells release glucagon, which makes the liver release glucose and raises it. Blood glucoseabout 4–7 mmol/LBeta cells: insulinwhen glucose risesMuscle, fat, livertake up and store glucoseAlpha cells: glucagonwhen glucose fallsLiverreleases glucoselowersraises
A push–pull system. Insulin is the only hormone that lowers blood glucose; several raise it, including glucagon, adrenaline, cortisol and growth hormone.

How muscle takes up glucose

Skeletal muscle takes up most of the glucose after a meal. Glucose enters through the transporter GLUT4, which is normally stored inside the cell. Insulin binding its receptor moves GLUT4 to the surface.

Figure 2 · Two keys to the same door

Insulin and muscle contraction both move GLUT4 transporters to the muscle cell surface A muscle cell stores GLUT4 glucose transporters inside. Insulin binding its receptor and muscle contraction through a separate pathway both move GLUT4 to the cell surface, letting glucose enter. Contraction works even when the cell is resistant to insulin. Muscle cellGLUT4 stores inside the cellInsulinbinds receptorContractionworks even withinsulin resistanceglucose enters through GLUT4Both signals moveGLUT4 to the surface,letting glucose in
Why exercise lowers glucose in diabetes. Contracting muscle takes up glucose through an insulin-independent route, and training improves insulin sensitivity for hours to days.

Muscle contraction moves GLUT4 to the surface through a separate, insulin-independent pathway. That is why exercise lowers glucose even in people with insulin resistance, and why regular training improves insulin sensitivity.

Diabetes

FeatureType 1Type 2
CauseAutoimmune destruction of beta cellsInsulin resistance with failing beta cells
Typical onsetChildhood or young adulthoodAdulthood; increasingly younger
Risk factorsGenetic and immuneInactivity, excess weight, family history, ancestry
TreatmentInsulin alwaysLifestyle, tablets, sometimes insulin
Acute dangerKetoacidosisVery high glucose with dehydration

Figure 3 · Glucose tolerance

Blood glucose after a glucose drink in normal tolerance, prediabetes and diabetes Three curves after a 75 gram glucose drink. Normal glucose returns below 7.8 millimoles per litre by two hours; in prediabetes it stays between 7.8 and 11.0; in diabetes it starts higher and stays above 11.1. 11.17.80306090120481216Minutes after 75 g glucose drinkBlood glucose (mmol/L)NormalPrediabetesDiabetes2-hour value:under 7.8 normal7.8–11.0 impaired11.1 or more diabetes
Insulin resistance shows first after meals. Commonly used diagnostic thresholds are shown; HbA1c reflects average glucose over about three months. Schematic curves.

HbA1c measures the proportion of haemoglobin with glucose attached, reflecting average glucose over about three months. Long-term high glucose damages small vessels (eyes, kidneys, nerves) and large vessels (heart, brain, legs).

Preventing type 2 diabetes

The Diabetes Prevention Program randomised 3,234 adults with raised glucose to placebo, metformin or a lifestyle programme aiming for 7% weight loss and at least 150 minutes of activity a week [1].

Figure 4 · Lifestyle prevents diabetes

Incidence of type 2 diabetes with placebo, metformin and lifestyle intervention Three bars: 11.0 new cases per 100 person-years with placebo, 7.8 with metformin and 4.8 with the lifestyle programme, which reduced incidence by 58 per cent. 11.0Placebo7.8Metformin4.8LifestyleNew diabetes per 100 person-yearsLifestyle:58% fewer cases(7% weight loss,150 min/week activity)Metformin:31% fewer cases
Lifestyle beat the drug. About 7 people needed the lifestyle programme for three years to prevent one case of diabetes [1].

Over about three years, the lifestyle programme reduced new diabetes by 58%, and metformin by 31% [1]. Lifestyle change was significantly more effective than the drug [1].

Exercise as treatment

Umpierre and colleagues pooled 47 trials in 8,538 people with type 2 diabetes [2]. Structured exercise lowered HbA1c by about 0.67%, with larger effects above 150 minutes a week [2].

Figure 5 · Exercise lowers long-term glucose

Reductions in HbA1c with different exercise approaches in type 2 diabetes Horizontal bars of HbA1c reduction: 0.89 per cent with more than 150 minutes a week of structured exercise, 0.73 with aerobic, 0.67 overall, 0.57 with resistance, 0.58 with activity plus diet advice, 0.36 with 150 minutes or less, and no change with activity advice alone. Structured exercise, more than 150 min/week−0.89%Structured aerobic exercise−0.73%Structured exercise overall−0.67%Structured resistance training−0.57%Activity advice plus diet advice−0.58%Structured exercise, 150 min/week or less−0.36%Activity advice aloneno changeFall in HbA1c versus control; 47 trials, 8,538 people with type 2 diabetes [2]
Supervised, sufficient exercise works best. Structured training lowered HbA1c by amounts comparable to some drugs; advice alone did not [2].

Aerobic, resistance and combined training all helped [2]. Activity advice alone did not change HbA1c unless combined with dietary advice [2]. Supervised, structured programmes are therefore worth the effort.

Practical skill · exercising people with diabetes

Check glucose before exercise if the patient uses insulin or sulfonylureas. Have fast-acting carbohydrate available. Inspect feet if neuropathy is present and choose suitable footwear. Avoid heavy straining with untreated proliferative retinopathy. Watch for delayed low glucose after long sessions.

SituationTypical guidance
Glucose low before exercise (on insulin)Take carbohydrate and recheck before starting
Glucose very high with ketones (type 1)Do not exercise; seek advice
Symptoms during exercise: shaky, sweaty, confusedStop; give fast-acting glucose; recheck
Peripheral neuropathyDaily foot checks; non-weight-bearing options if ulcers

Clinical relevance for the physiotherapist

  • Prevention. Activity and weight loss prevent diabetes more effectively than a drug [1].
  • Treatment. Aim for structured exercise above 150 minutes a week where possible [2].
  • Hypoglycaemia. Know the signs and carry glucose.
  • Complications. Assess sensation, circulation and feet; adapt for retinopathy and kidney disease.
  • Contraction-driven uptake. Even short activity after meals lowers glucose.

Assessment and application

SituationInterpretationAction
Overweight adult with HbA1c in prediabetic rangeHigh risk [1]Activity programme with weight-loss support
Patient with type 2 diabetes, sedentary, HbA1c highExercise can lower HbA1c [2]Supervised aerobic and resistance training
Patient on insulin becomes sweaty and confused mid-sessionHypoglycaemiaStop; fast glucose; recheck
Numb feet and a small blisterNeuropathy with ulcer riskStop weight-bearing on it; refer to foot care

Common mistakes

  • Giving activity advice without structure or follow-up [2].
  • Assuming diabetes medication makes lifestyle change unnecessary [1].
  • Exercising a type 1 patient with high glucose and ketones.
  • Ignoring feet in patients with neuropathy.
  • Forgetting delayed hypoglycaemia after long sessions.

Exam preparation

Long answer

Describe the actions of insulin and the regulation of its secretion. Add a note on diabetes mellitus.

  • Islet cells and hormones (table).
  • Feedback with glucagon (Figure 1).
  • Actions on muscle, liver and fat; GLUT4 (Figure 2).
  • Diabetes types and tests (Figure 3).
  • Prevention and exercise treatment [1, 2].

Short notes

  • Glucagon.
  • GLUT4 and exercise.
  • HbA1c.
  • Diabetes Prevention Program [1].

Viva and practical

  • “Which hormone lowers glucose?” — insulin.
  • “How does exercise lower glucose without insulin?” — contraction moves GLUT4.
  • “How much exercise lowers HbA1c most?” — more than 150 min/week structured [2].
  • OSCE: screen a diabetic patient before exercise.

Current evidence

Exam and traditional teaching

Diabetes is managed mainly with drugs; exercise is general advice.

What the evidence adds

Lifestyle intervention prevents diabetes better than metformin [1].

Structured exercise lowers HbA1c meaningfully; advice alone does not [2].

What the student should understand

Muscle is the body’s largest glucose sink. Using it regularly is treatment, not just advice.

Check yourself

10 questions on this page. Tap one to see the answer and the reasoning.

Q1. In the Diabetes Prevention Program, the lifestyle intervention reduced the incidence of diabetes by about:
  1. (A) 10%
  2. (B) 31%
  3. (C) 58%
  4. (D) 90%

Answer: (C) Lifestyle reduced incidence by 58%, versus 31% with metformin [1].

Q2. The lifestyle programme aimed for at least how much physical activity per week?
  1. (A) 30 minutes
  2. (B) 75 minutes
  3. (C) 150 minutes
  4. (D) 500 minutes

Answer: (C) The goals were 7% weight loss and at least 150 minutes of activity per week [1].

Q3. How many people needed the lifestyle programme for three years to prevent one case of diabetes?
  1. (A) About 7
  2. (B) About 70
  3. (C) About 700
  4. (D) About 2

Answer: (A) The number needed to treat was 6.9 [1].

Q4. Diabetes incidence with placebo, metformin and lifestyle was:
  1. (A) 11.0, 7.8 and 4.8 per 100 person-years
  2. (B) 4.8, 7.8 and 11.0
  3. (C) All about 8
  4. (D) Not reported

Answer: (A) Incidence was 11.0, 7.8 and 4.8 cases per 100 person-years [1].

Q5. Structured exercise training in type 2 diabetes lowered HbA1c by about:
  1. (A) 0.07%
  2. (B) 0.67%
  3. (C) 6.7%
  4. (D) No change

Answer: (B) Overall reduction was about 0.67% [2].

Q6. Structured exercise of more than 150 minutes per week lowered HbA1c by about:
  1. (A) 0.36%
  2. (B) 0.89%
  3. (C) 2%
  4. (D) 0%

Answer: (B) More than 150 minutes was associated with about 0.89% reduction [2].

Q7. Physical activity advice alone, without diet advice:
  1. (A) Lowered HbA1c by 1%
  2. (B) Was not associated with HbA1c change
  3. (C) Raised HbA1c
  4. (D) Cured diabetes

Answer: (B) Advice alone was not associated with change [2].

Q8. Which types of structured exercise lowered HbA1c?
  1. (A) Only aerobic
  2. (B) Aerobic, resistance and combined
  3. (C) Only resistance
  4. (D) None

Answer: (B) All three types were associated with reductions [2].

Q9. Muscle contraction moves GLUT4 to the cell surface:
  1. (A) Only when insulin is present
  2. (B) Through a pathway independent of insulin
  3. (C) Never
  4. (D) Only in the liver

Answer: (B) This is why exercise lowers glucose even with insulin resistance; structured exercise improves HbA1c [2].

Q10. A practical message for people at high risk of diabetes is:
  1. (A) Medication is always better than lifestyle
  2. (B) Weight loss and regular activity substantially reduce risk
  3. (C) Activity has no effect
  4. (D) Only diet matters

Answer: (B) Lifestyle was more effective than metformin [1].

Quick review

Key takeaways

  • Beta cells: insulin; alpha: glucagon; delta: somatostatin.
  • Insulin lowers glucose; several hormones raise it.
  • Insulin and contraction both move GLUT4 to the muscle surface.
  • Lifestyle cut diabetes incidence by 58% [1].
  • Structured exercise lowers HbA1c about 0.67%; more with over 150 min/week [2].
  • Carry glucose; check feet; avoid exercise with ketones.

Further reading

SourceWhy it earns its place
Knowler WC et al. — NEJM, 2002The Diabetes Prevention Program [1]
Umpierre D et al. — JAMA, 2011Exercise and HbA1c [2]
Williams Textbook of EndocrinologyPancreatic hormones

References

  1. Knowler WC, Barrett-Connor E, Fowler SE, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. New England Journal of Medicine. 2002;346(6):393–403. doi:10.1056/NEJMoa012512 PMID 11832527 Randomised controlled trial
  2. Umpierre D, Ribeiro PAB, Kramer CK, et al. Physical activity advice only or structured exercise training and association with HbA1c levels in type 2 diabetes: a systematic review and meta-analysis. JAMA. 2011;305(17):1790–1799. doi:10.1001/jama.2011.576 PMID 21540423 Systematic review and meta-analysis

Related topics

Reviewed by the Physiotherapist India Team. · Human Physiology contents