BiologyICSE Class 10 · Endocrine System

Thyroid and Adrenal Glands: Thyroxine, Cortical Hormones and Adrenaline (ICSE Class 10 Biology)

Updated 16 October 2026 · Fact-checked

The butterfly-shaped thyroid in the neck secretes iodine-containing thyroxine, which controls the basal metabolic rate, growth and mental development. Too little causes cretinism in children and myxoedema in adults; too much causes exophthalmic goitre. The cap-like adrenals on the kidneys secrete cortical hormones for salt and water balance, and adrenaline for emergencies.

Understand Thyroid and Adrenal Glands

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

Thyroxine (the only thyroid hormone in the syllabus).

Contains iodine.
Controls the basal metabolic rate (BMR): the rate at which cells use oxygen and food to release energy.
Needed for normal physical growth and mental development.

Thyroid disorders.

Condition	Cause	Features
Cretinism	hyposecretion in children	stunted growth, mental retardation
Myxoedema	hyposecretion in adults	low BMR, puffy face and skin, lethargy, weight gain
Simple goitre	iodine deficiency in diet	enlarged thyroid seen as a neck swelling
Exophthalmic goitre	hypersecretion	bulging eyes, high BMR, nervousness, weight loss, fast heartbeat

Iodised salt prevents simple 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 an inner medulla, which secrete different hormones.

Cortical hormones (adrenal cortex).

Regulate salt and water balance: for example, aldosterone keeps sodium (and water) in the body.
Help in carbohydrate metabolism and in coping with long-term stress.
Small amounts of sex hormones.
Hyposecretion lowers salt and water retention and blood sugar (Addison's disease).

Adrenaline (adrenal medulla): the emergency hormone. Released in fear, anger or excitement ('fight or flight'):

Faster heartbeat and higher blood pressure.
Faster, deeper breathing.
Raises blood glucose (liver glycogen → glucose).
Dilates pupils; diverts blood to skeletal muscles; slows digestion.

These effects resemble those of the sympathetic nervous system, which works with it.

Comparison.

Feature	Thyroid	Adrenal
Location	neck, on the trachea	on top of each kidney
Shape	butterfly (H)	cap-like
Hormones	thyroxine	cortical hormones; adrenaline
Key role	metabolic rate, growth	salt-water balance; emergency response

Flow chart: emergency. Danger seen → brain → sympathetic nerves → adrenal medulla → adrenaline into blood → heart, lungs, liver, muscles → faster heartbeat and breathing, more glucose → ready to fight or run.

Draw-and-label checklist: positions. Neck outline with trachea; thyroid as two lobes joined by an isthmus across the trachea. Kidneys with a cap-shaped adrenal on each; label cortex and medulla in a section if asked.

Thyroid and Adrenal Glands: key facts

Thyroxine: Contains iodine
Controls BMR
Needed for growth and mental development; Only thyroxine is in the syllabus.
Thyroid disorders: Child hypo cretinism
Adult hypo myxoedema
Iodine lack simple goitre
Hyper exophthalmic goitre; Give hypo or hyper each time.
Adrenal hormones: Cortex: cortical hormones, salt and water balance, carbohydrate metabolism | Medulla: adrenaline, emergency hormone, raises heart rate and blood glucose; Adrenaline acts like the sympathetic system.

Child hypo	cretinism
Adult hypo	myxoedema
Iodine lack	simple goitre
Hyper	exophthalmic goitre

How to answer Thyroid and Adrenal Glands questions

ICSE shows a picture of a disorder, gives a stress case, or labels glands on a body outline, and asks for the gland, hormone, disorder and whether it is hypo- or hypersecretion.

1Identify the gland from the location: neck = thyroid; above kidneys = adrenal.
2For a disorder picture, give the name, the hormone and hypo or hyper (and age group).
3For stress or fear cases, name adrenaline and list two effects.
4Link iodine to thyroxine and simple goitre.
5Use full numbering exactly as the question sets it out.

Thyroid and Adrenal Glands in real life

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

Iodised salt

Suppose a family switches from iodised table salt to an expensive uniodised rock salt for several years, and the mother slowly develops a swelling at the front of her neck.

Explain the cause and a simple remedy.

Try it first, then show the solutionSolution

The thyroid needs iodine to make thyroxine.
Without enough iodine, thyroxine is low and the pituitary keeps sending TSH.
Constant stimulation enlarges the thyroid: simple goitre.
Using iodised salt supplies the missing iodine.

Answer: Iodine-deficiency goitre; prevented by iodised salt.

Memory hook: No iodine, big thyroid.

A dog chases you

Suppose a stray dog suddenly chases you on the way home, and you sprint faster than you thought you could, heart pounding.

Which hormone helped, and how?

Try it first, then show the solutionSolution

Fear triggers the adrenal medulla through sympathetic nerves.
Adrenaline is released into the blood.
It raises heartbeat and breathing, and releases glucose from liver glycogen.
More oxygen and glucose reach the leg muscles for the sprint.

Answer: Adrenaline, which raises heart rate, breathing and blood glucose for extra energy.

Memory hook: Adrenaline = adrenaline rush.

Tricks to remember Thyroid and Adrenal Glands

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

Cretin Child, Myxo Mature
C for Child = cretinism; M for Mature = myxoedema.
Use it when: Age-based thyroid disorders.
Eyes Exit = Exophthalmic
Too much thyroxine makes the eyes bulge out (ex = out, ophthalmos = eye).
Use it when: Hypersecretion disorder.
3 Fs for adrenaline
Fight, Flight, Fright.
Use it when: When adrenaline is released.

Thyroid and Adrenal Glands: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Mineral for thyroxine · 1 mark · MCQBoard level

The mineral needed to make thyroxine is:
(a) calcium (b) iron (c) iodine (d) sodium

Try it first, then show the solutionSolution

Thyroxine contains iodine.

Answer: (c) iodine.

Example 2: Fast heart, weight loss · 2 marks · Short answerBoard level

A woman has a fast heartbeat, feels hot all the time and loses weight although she eats well. (a) Is her thyroxine level likely to be high or low? Explain using BMR. (b) Name the disorder if her eyes also bulge. (A thyroid defect picture was asked in 2025.)

Try it first, then show the solutionSolution

(a) High: excess thyroxine raises the basal metabolic rate, so food is used up fast, extra heat is produced and weight falls (1 mark).
(b) Exophthalmic goitre, due to hypersecretion of thyroxine (1 mark).

Answer: (a) High; raised BMR burns food fast and produces heat. (b) Exophthalmic goitre (hypersecretion).

Example 3: Why childhood matters · 2 marks · Short answerHarder board level

Explain why a lack of thyroxine in early childhood has more serious, lasting effects than the same lack in an adult.

Try it first, then show the solutionSolution

In childhood thyroxine is needed for normal physical growth and mental development; its lack causes cretinism, with stunted growth and mental retardation that cannot be fully reversed (1 mark).
In an adult, growth and brain development are complete, so the lack (myxoedema) mainly lowers the BMR, causing lethargy and puffiness, which treatment with thyroxine can correct (1 mark).

Answer: Children need thyroxine for growth and brain development (cretinism is lasting); adults mainly suffer a low BMR (myxoedema), which is treatable.

Example 4: How adrenaline helps escape · 3 marks · Short answerHarder board level

Explain how each of these effects of adrenaline helps a person escape from danger: (a) faster, deeper breathing; (b) higher blood glucose; (c) blood diverted from the gut to skeletal muscles.

Try it first, then show the solutionSolution

(a) More oxygen enters the blood for respiration in the muscles (1 mark).
(b) More glucose is available as fuel for respiration, releasing more energy for running or fighting (1 mark).
(c) Working muscles receive more oxygen and glucose, while digestion, which is not urgent, is slowed (1 mark).

Answer: (a) More oxygen; (b) more fuel; (c) more blood to working muscles; all give extra energy for fight or flight.

Example 5: Salt and water · 3 marks · Case-basedHOTS / competency

Suppose a patient's adrenal cortex is damaged and he loses a lot of salt in urine and feels weak and dizzy. (a) Which hormones are lacking? (b) Explain the salt loss. (c) Would his response to sudden fright be affected? Explain.

Try it first, then show the solutionSolution

(a) Cortical hormones (such as aldosterone) (1 mark).
(b) These hormones keep sodium and water in the body; without them salt and water are lost in urine (1 mark).
(c) Not necessarily, because adrenaline comes from the medulla, which may still work (1 mark).

Answer: (a) Cortical hormones. (b) Sodium not retained. (c) Adrenaline from the medulla may still be released.

Example 6: Always feeling cold · 3 marks · Case-basedHOTS / competency

Suppose a 40-year-old woman feels tired, gains weight, has a puffy face and always feels cold. (a) Name the likely condition and the hormone problem. (b) Explain why she feels cold, using BMR. (c) Why does the doctor prescribe a thyroxine tablet every day rather than a single large dose?

Try it first, then show the solutionSolution

(a) Myxoedema: hyposecretion of thyroxine in an adult (1 mark).
(b) Low thyroxine lowers the basal metabolic rate, so cells respire more slowly and produce less heat (1 mark).
(c) Hormones are used up and broken down in the body all the time, so a steady daily supply is needed to keep the level normal (1 mark).

Answer: (a) Myxoedema (adult hypothyroidism). (b) Low BMR, less heat produced. (c) Thyroxine is used up continually, so it must be replaced daily.

Where students lose marks in Thyroid and Adrenal Glands

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

Mistake: Disorder not linked to the hormone
CISCE examiners' comments (2025): shown a picture, candidates failed to relate the defect to the specific hormone and its over- or under-secretion.
Do this: Name the disorder, hormone and hypo or hyper.
Usually costs: 1 mark.
Mistake: Glands not matched to hormones
CISCE examiners' comments (2025): on a body outline of endocrine glands, candidates were unable to correlate glands with their hormones and did not follow the numbering pattern.
Do this: Learn gland-location-hormone as a set; follow the question's numbering.
Usually costs: 1-2 marks.
Mistake: Vitamin K for a mineral
CISCE examiners' comments (2024): asked for mineral elements, candidates wrote vitamin K instead of calcium for clotting; the same question needed iodine for thyroxine.
Do this: Iodine for thyroxine; calcium for clotting.
Usually costs: 1 mark.

Exam tips

Thyroid: neck, butterfly, thyroxine with iodine.
Cretinism (child), myxoedema (adult), exophthalmic goitre (excess).
Adrenal: cortex for salt and water, medulla for adrenaline.
Adrenaline = emergency hormone.

Practice questions on Thyroid and Adrenal Glands

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

Q1 · 1 mark · MCQBoard level
The hormone called the 'emergency hormone' is:
(a) insulin (b) thyroxine (c) adrenaline (d) oxytocin
Hint
Fight or flight.
Answer
(c) adrenaline.
Q2 · 1 mark · Very short answerBoard level
Name the disorder caused by lack of iodine in the diet.
Hint
Neck swelling.
Answer
Simple goitre.
Q3 · 1 mark · Assertion-reasonHarder board level
Assertion (A): Adrenaline raises the level of glucose in blood.
Reason (R): Adrenaline converts liver glycogen into glucose.
(a) (A) is true and (R) is false.
(b) (A) is false and (R) is true.
(c) Both (A) and (R) are true, and (R) is the correct explanation of (A).
(d) Both (A) and (R) are true, but (R) is not the correct explanation of (A).
Hint
Energy in emergency.
Answer
(c).
Q4 · 2 marks · Short answerHarder board level
Describe the location and shape of the thyroid gland.
Hint
Neck, two lobes.
Answer
In the neck, below the larynx; butterfly (H)-shaped with two lobes on either side of the trachea joined by an isthmus.
Q5 · 2 marks · Short answerHarder board level
State two functions of thyroxine.
Hint
BMR.
Answer
Regulates the basal metabolic rate; promotes normal physical growth and mental development.
Q6 · 2 marks · Short answerHarder board level
Name the two parts of the adrenal gland and one hormone or group of hormones from each.
Hint
Outer and inner.
Answer
Cortex: cortical hormones (such as aldosterone). Medulla: adrenaline.
Q7 · 2 marks · Short answerHarder board level
Adrenaline takes effect more slowly than the sympathetic nerves but its effects last longer. Explain why, in terms of how each message travels.
Hint
Blood versus nerve.
Answer
Adrenaline is carried by the blood, so it takes some seconds to reach its targets and stays in the blood until it is broken down; sympathetic messages travel as fast nerve impulses that stop as soon as the nerve stops firing.
Q8 · 3 marks · Case-basedHOTS / competency
Read and answer.
Suppose a newborn in a remote area, whose mother's diet lacked iodine, grows slowly and shows delayed mental development by age three.
(a) Name the disorder. (1)
(b) Which hormone and gland are involved? (1)
(c) Suggest one public-health measure to prevent it. (1)
Hint
Child, low thyroxine.
Answer
(a) Cretinism. (b) Thyroxine; thyroid. (c) Use of iodised salt (iodine supplements for pregnant mothers).

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.What does BMR stand for?Show answer
Basal metabolic rate.
2.Where are the adrenal glands?Show answer
On top of each kidney.
3.Which disorder causes bulging eyes?Show answer
Exophthalmic goitre.
4.What does aldosterone regulate?Show answer
Salt (sodium) and water balance.
5.Which part of the adrenal makes adrenaline?Show answer
Medulla.

Thyroid and Adrenal Glands: frequently asked questions

Do I need calcitonin or T3?

No. The syllabus specifies only thyroxine for the thyroid.

Is adrenaline the same as epinephrine?

Yes. Epinephrine is another name for adrenaline.

Can goitre be due to too much or too little thyroxine?

Simple goitre comes with low thyroxine from iodine lack; exophthalmic goitre comes with too much thyroxine.

How many cortical hormones should I name?

Their roles matter most: salt and water balance and carbohydrate metabolism; naming aldosterone as an example is enough.