Endocrine System ICSE Class 10: Pituitary, Thyroid, Adrenal and Pancreas

What Endocrine System is about

Weightage: CISCE publishes no chapter or unit weightage for ICSE Biology. Endocrine System is in the 3. Human Anatomy and Physiology (iv) part of the 2027 syllabus and can be asked in both Section A and Section B of the 80-mark paper.Source: CISCE ICSE Biology (Science Paper 3) syllabus, examination year 2027

Key concepts

Endocrine and exocrine glands

Endocrine glands	Exocrine glands
ductless	have ducts
secretion (hormone) poured directly into blood	secretion carried by ducts to a surface or cavity
act on distant target organs	act locally
e.g. thyroid, pituitary, adrenal	e.g. salivary, sweat, gastric glands

The pancreas is both: its exocrine part makes pancreatic juice (sent by a duct to the duodenum), and its endocrine part, the islets of Langerhans, makes hormones. Such a gland is called a mixed (heterocrine) gland.

Worked example

Why is the pancreas called a mixed gland?

Try it first, then show the solutionSolution

1. Its acini secrete pancreatic juice through a duct (exocrine).
2. Its islets of Langerhans secrete insulin and glucagon into the blood (endocrine).

Answer: It has both exocrine and endocrine parts.

Pituitary gland

Location and shape: a small, pea-sized gland at the base of the brain, attached to the hypothalamus by a stalk. It is called the master gland because its tropic hormones control other glands.

Hormones:

• Growth hormone (GH): growth of bones and muscles.
• Hypo in childhood: dwarfism (short but proportionate, normal intelligence).
• Hyper in childhood: gigantism (abnormally tall).
• Hyper in adults: acromegaly (enlarged hands, feet, jaw and face).
• Tropic hormones: stimulate other endocrine glands: TSH (thyroid), ACTH (adrenal cortex), FSH and LH (gonads).
• ADH (antidiuretic hormone, vasopressin): increases reabsorption of water in kidney tubules. Hypo: diabetes insipidus (large volumes of dilute urine, thirst).
• Oxytocin: causes contraction of the uterus during childbirth and the release (ejection) of milk.

Worked example

Which pituitary hormone (a) affects urination, (b) causes strong uterine contractions at childbirth?

Try it first, then show the solutionSolution

1. (a) ADH controls water reabsorption, so it affects the volume of urine.
2. (b) Oxytocin.

Answer: (a) ADH (vasopressin) (b) Oxytocin

Thyroid gland

Location and shape: in the neck, butterfly-shaped (H-shaped), with two lobes on either side of the trachea, just below the larynx, joined by a narrow isthmus.

Hormone: thyroxine, which contains iodine. It controls the basal metabolic rate (BMR), growth and mental development.

• Hypo in children: cretinism (stunted growth, mental retardation).
• Hypo in adults: myxoedema (low BMR, puffy face, lethargy, weight gain).
• Iodine deficiency: simple goitre, an enlarged thyroid seen as a swelling in the neck.
• Hyper: exophthalmic goitre (bulging eyes, high BMR, nervousness, weight loss).

Worked example

Why is iodised salt recommended in hilly areas far from the sea?

Try it first, then show the solutionSolution

1. Thyroxine needs iodine.
2. Soil and food in such areas may lack iodine.
3. Iodine deficiency causes simple goitre; iodised salt prevents it.

Answer: To supply iodine for thyroxine and prevent goitre.

Adrenal glands

Location and shape: a pair of cap-like (triangular) glands, one on top of each kidney. Each has an outer cortex and inner medulla.

Cortical hormones (from the cortex): regulate salt and water balance (for example, aldosterone keeps sodium in the body), help carbohydrate metabolism, and include small amounts of sex hormones. Hyposecretion of the cortex lowers salt and water retention and blood sugar (Addison's disease).

Adrenaline (from the medulla): the emergency ('fight or flight') hormone. It increases heart rate and blood pressure, raises blood glucose (glycogen → glucose), increases breathing rate, dilates pupils, diverts blood to muscles and slows digestion. Its effects resemble those of the sympathetic nervous system.

Worked example

Why is adrenaline called the emergency hormone? Give two of its effects.

Try it first, then show the solutionSolution

1. It is released in fear, anger or excitement, preparing the body to fight or run.
2. Effects: faster heartbeat; more glucose in the blood (also faster breathing, dilated pupils).

Answer: It prepares the body for emergencies; faster heartbeat and raised blood sugar.

Pancreas: insulin and glucagon

Location and shape: a leaf-like (elongated) gland lying behind the stomach, in the loop of the duodenum.

Islets of Langerhans:

• Beta cells secrete insulin, which lowers blood glucose: it helps cells take up glucose and makes the liver and muscles convert glucose to glycogen.
• Hypo: diabetes mellitus: high blood sugar, glucose in urine, frequent urination, thirst, tiredness.
• Hyper: hypoglycaemia: blood sugar too low; weakness, fainting.
• Alpha cells secrete glucagon, which raises blood glucose by converting liver glycogen back to glucose.

Insulin and glucagon work in opposite directions to keep blood glucose steady.

Worked example

Distinguish between diabetes mellitus and diabetes insipidus on the basis of the gland concerned.

Try it first, then show the solutionSolution

1. Diabetes mellitus: pancreas (islets of Langerhans), insufficient insulin.
2. Diabetes insipidus: pituitary, insufficient ADH.

Answer: Pancreas versus pituitary.

Feedback control: TSH and thyroxine

The amount of a hormone is kept steady by feedback: the level of the hormone in the blood controls its own production.

1. When thyroxine in the blood is low, the pituitary releases more TSH (thyroid-stimulating hormone).
2. TSH stimulates the thyroid to secrete more thyroxine.
3. When thyroxine rises above normal, it inhibits TSH secretion by the pituitary.
4. Less TSH → less thyroxine, and the level falls back to normal.

This is negative feedback: the response reverses the change, like a thermostat.

Worked example

What happens to TSH secretion when the blood level of thyroxine is high?

Try it first, then show the solutionSolution

1. High thyroxine acts on the pituitary.
2. TSH secretion is reduced.
3. The thyroid then secretes less thyroxine.

Answer: TSH secretion decreases.

Endocrine System in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Pituitary Gland and Feedback Control
• Thyroid and Adrenal Glands
• Pancreas: Insulin and Glucagon

Endocrine System: key facts

Negative feedback loop

$\text{low thyroxine}\to \text{more TSH}\to \text{more thyroxine}\to \text{less TSH}$

Keeps thyroxine steady.

Blood glucose control

$\text{insulin: glucose}\to \text{glycogen};\text{glucagon: glycogen}\to \text{glucose}$

Opposite actions.

Too little vs too much growth hormone

$\text{hypo (child): dwarfism};\text{hyper (child): gigantism};\text{hyper (adult): acromegaly}$

Pituitary.

Thyroxine disorders

$\text{hypo: cretinism (child), myxoedema (adult)};\text{hyper: exophthalmic goitre}$

Iodine lack: simple goitre.

Endocrine System: diagrams to practise

Practise each one on paper: draw it from the checklist, then tick off every label.

How the board asks Endocrine System

The question patterns to expect, and the method that works for each.

Tricks to remember Endocrine System

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Insulin puts sugar IN (to cells)

  INsulin pushes glucose INto cells and INto glycogen; glucaGON makes glycogen GO back to glucose.

  Use it when: Insulin vs glucagon.

• Mellitus = Mellow (sweet)

  Diabetes MELLitus: honey-sweet urine (glucose), pancreas. INsipidus: tasteless urine, pituitary ADH.

  Use it when: The two diabetes types.

• Oxytocin = Ox-strength push

  Oxytocin gives the strong push of uterine contractions at birth.

  Use it when: Oxytocin's role.

• Ad-renal sits on the renal

  AD-RENAL = on (ad) the kidney (renal).

  Use it when: Location of adrenals.

Endocrine System: board-level solved questions

Ordered from board level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section B style)

Read the situation, then answer every part. In the board paper this is a 6-mark question split into 1 + 2 + 2 + 1 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Endocrine System

The slips examiners see most often, and what to write instead.

• ✗Mistake: Adrenaline for vasopressin

  CISCE examiners' comments, 2024: for the hormone that affects urination, candidates confused adrenaline and vasopressin.

  Wrong working

  Adrenaline controls urination.

  Right working

  ADH (vasopressin) controls water reabsorption and hence urine volume.

  ✓Do this: Anti-DIURETIC = against urine.

  Usually costs: 1 mark.

• ✗Mistake: Hormones named instead of glands

  CISCE examiners' comments, 2024: distinguishing diabetes mellitus and insipidus by gland, candidates wrote hormone names.

  Wrong working

  Mellitus: insulin; insipidus: ADH.

  Right working

  Mellitus: pancreas; insipidus: pituitary.

  ✓Do this: Answer exactly what is asked (gland).

  Usually costs: 1-2 marks.

• ✗Mistake: Incomplete hormone definition

  CISCE examiners' comments, 2024: candidates did not mention secretion by endocrine glands or transport by blood.

  Wrong working

  A hormone is a chemical messenger.

  Right working

  A chemical secreted by an endocrine gland directly into the blood and carried to a target organ.

  ✓Do this: Gland + blood + target.

  Usually costs: 1 mark.

• ✗Mistake: Oxytocin confused with sex hormones

  CISCE examiners' comments, 2025: for the hormone causing uterine contractions in childbirth, candidates chose oestrogen or progesterone.

  Wrong working

  Progesterone causes uterine contractions.

  Right working

  Oxytocin (pituitary) causes them; progesterone keeps the uterus calm during pregnancy.

  ✓Do this: Birth push = oxytocin.

  Usually costs: 1 mark.

• ✗Mistake: Disorder not linked to hormone level

  CISCE examiners' comments, 2025: shown a picture of a defect, candidates failed to relate it to a specific hormone and to over- or under-secretion.

  Wrong working

  The person has a thyroid problem.

  Right working

  Exophthalmic goitre: hypersecretion of thyroxine.

  ✓Do this: Always give gland, hormone and hypo/hyper.

  Usually costs: 1 mark.

Practice questions on Endocrine System

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQBoard level

   The gland called the master gland is the:
   (a) thyroid
   (b) adrenal
   (c) pituitary
   (d) pancreas

   Hint

   Tropic hormones.

   Answer

   (c)

2. Q2 · 1 mark · MCQBoard level

   A swelling in the neck due to lack of iodine is:
   (a) exophthalmic goitre
   (b) simple goitre
   (c) myxoedema
   (d) cretinism

   Hint

   Iodine deficiency.

   Answer

   (b)

3. Q3 · 1 mark · Assertion-reasonHarder board level

   Assertion (A): Insulin deficiency causes glucose to appear in urine.
   Reason (R): Without insulin, blood glucose rises beyond what the kidneys can reabsorb.
   (a) Both (A) and (R) are true, and (R) is the correct explanation for (A).
   (b) Both (A) and (R) are true, but (R) is not the correct explanation for (A).
   (c) (A) is true and (R) is false.
   (d) (A) is false and (R) is true.

   Hint

   Reabsorption limit.

   Answer

   (a)

4. Q4 · 3 marks · Very short answerBoard level

   Name the hormone: (a) the emergency hormone; (b) that stimulates the adrenal cortex; (c) that causes milk ejection.

   Hint

   Adrenal, pituitary, pituitary.

   Answer

   (a) Adrenaline (b) ACTH (c) Oxytocin

5. Q5 · 2 marks · Short answerHarder board level

   Give two effects of adrenaline on the body.

   Hint

   Heart and sugar.

   Answer

   Increases heart rate and blood pressure; raises blood glucose (also dilates pupils, faster breathing).

6. Q6 · 2 marks · Short answerHarder board level

   Why do the effects of adrenaline resemble those of the sympathetic nervous system?

   Hint

   Both for emergencies.

   Answer

   Both prepare the body for emergencies ('fight or flight'): faster heartbeat and breathing, dilated pupils, more blood to muscles.

7. Q7 · 2 marks · Short answerHarder board level

   Give one function of cortical hormones of the adrenal gland and one effect of their hyposecretion.

   Hint

   Salt and water.

   Answer

   Function: regulating salt and water balance (or carbohydrate metabolism). Hyposecretion: loss of salt and water, low blood sugar and weakness (Addison's disease).

8. Q8 · 3 marks · Case-basedHarder board level

   A child is unusually short but well-proportioned and of normal intelligence; another child is short, with poor mental development. Identify the likely hormone problem in each.

   Hint

   GH vs thyroxine.

   Answer

   First: dwarfism, hyposecretion of growth hormone (pituitary). Second: cretinism, hyposecretion of thyroxine (thyroid).

9. Q9 · 2 marks · Short answerHOTS / competency

   Why is a hormone needed only in very small amounts, yet its absence has major effects? Use insulin as the example.

   Hint

   Regulators, not raw materials.

   Answer

   Hormones act as chemical signals that switch processes on or off in target cells; a tiny amount of insulin controls glucose uptake and storage by the whole body, so its absence disturbs blood sugar regulation completely.

10. Q10 · 3 marks · Short answerHOTS / competency

    A person has high TSH and low thyroxine. Suggest a likely cause and a symptom.

    Hint

    Thyroid not responding.

    Answer

    The thyroid is underactive (for example, lack of iodine), so thyroxine is low and the pituitary keeps secreting TSH. Symptoms: low BMR, lethargy, weight gain or a goitre.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.Why is the pituitary called the master gland?Show answer

   Its tropic hormones control other endocrine glands.

2. 2.Element needed for thyroxine?Show answer

   Iodine.

3. 3.Hormone that lowers blood glucose?Show answer

   Insulin.

4. 4.Hormone that raises blood glucose from liver glycogen?Show answer

   Glucagon (adrenaline also does this in emergencies).

5. 5.Disorder from hypersecretion of growth hormone in adults?Show answer

   Acromegaly.

6. 6.Disorder from thyroxine deficiency in children?Show answer

   Cretinism.

7. 7.Location of the adrenal glands?Show answer

   On top of the kidneys.

8. 8.Which tropic hormone stimulates the thyroid?Show answer

   TSH (thyroid-stimulating hormone).

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Can you define a hormone with three key points?
• ☐Can you locate the four glands on a body outline?
• ☐Can you name the disorders of GH, thyroxine and insulin imbalance?
• ☐Can you distinguish the two types of diabetes?
• ☐Can you explain the TSH feedback loop?

Endocrine System: frequently asked questions