Endocrine System: Hormones, Glands and Their Functions
Your body is like a busy school. Different organs have different jobs, and they must work together at the right time. The endocrine system is like the school announcement system. It sends chemical messages that tell the body when to grow, use food for energy, sleep, respond to danger, and prepare for reproduction.
These chemical messages are called hormones. They are tiny, but their effects are huge.
This guide is written as simple Biology notes for Classes 6 to 10. It explains the main hormones and glands, their functions, important diagrams to practise, common disorders, exam tips, solved questions, and practice questions.
This article is for learning only. For any health concern, always speak to a doctor or a qualified health professional.
What is the endocrine system?
The endocrine system is a group of glands that make hormones and release them directly into the blood.
These hormones travel through the bloodstream and reach specific organs or cells. The organs or cells that respond to a hormone are called target organs or target cells.
For example:
The pancreas releases insulin.
Insulin travels in the blood.
It acts on body cells, liver cells, and muscle cells.
These cells take in glucose from the blood.
Blood sugar level becomes normal.
The endocrine system controls many body activities, such as:
Growth and development
Metabolism, or how the body uses food for energy
Blood sugar balance
Stress response
Sleep cycle
Reproduction
Water and salt balance
Mood and body temperature
The endocrine system works more slowly than the nervous system, but its effects usually last longer.
What are hormones and how do they work?
Hormones are chemical messengers made by endocrine glands. They are released in very small amounts, but they can cause powerful changes in the body.
Think of hormones like letters sent through the blood. Each letter has a message, but only the correct receiver can understand it.
How hormones work
Most hormones work in these steps:
An endocrine gland receives a signal.
The gland makes and releases a hormone.
The hormone enters the blood.
It travels to target cells.
Target cells have special receptors.
The hormone fits into the receptor.
The cell responds.
A simple example is adrenaline.
When a dog suddenly barks near you:
Your brain senses danger.
Your adrenal glands release adrenaline.
Your heart beats faster.
Breathing becomes quicker.
More blood goes to muscles.
You become ready to run or react.
This is called the fight or flight response.
Endocrine glands and exocrine glands are different
Glands are organs that produce useful substances. There are two main types: endocrine glands and exocrine glands.
Feature | Endocrine glands | Exocrine glands |
Ducts | Do not have ducts | Have ducts |
Where secretion goes | Directly into blood | Through ducts to a surface or cavity |
Main secretion | Hormones | Sweat, saliva, enzymes, oil, mucus |
Speed of action | Usually slower | Usually faster at the place of release |
Example | Pituitary gland, thyroid gland, adrenal gland | Sweat glands, salivary glands, sebaceous glands |
Function | Control body activities through hormones | Help in digestion, cooling, lubrication, and protection |
The pancreas is special because it works as both an endocrine and an exocrine gland.
As an endocrine gland, it releases insulin and glucagon into the blood.
As an exocrine gland, it releases digestive enzymes into the small intestine.
Major endocrine glands and their hormones
Here is a student-friendly chart of the major endocrine glands and the hormones they produce.
Endocrine gland | Location | Main hormones | Main functions |
Pituitary gland | Below the brain | Growth hormone, TSH, ACTH, FSH, LH, ADH | Growth, control of other glands, water balance |
Thyroid gland | Front of neck | Thyroxine | Metabolism, growth, body temperature |
Parathyroid glands | Behind thyroid | Parathyroid hormone | Calcium balance |
Adrenal glands | Above kidneys | Adrenaline, cortisol, aldosterone | Stress response, salt balance, blood pressure |
Pancreas | Behind stomach | Insulin, glucagon | Blood sugar control |
Pineal gland | Brain | Melatonin | Sleep and wake cycle |
Thymus gland | Upper chest | Thymosin | Immune system development |
Ovaries | Lower abdomen in females | Oestrogen, progesterone | Female reproductive changes, menstrual cycle |
Testes | Scrotum in males | Testosterone | Male reproductive changes, sperm production |
Diagram suggestion for students
Draw a simple outline of the human body and mark:
Pituitary and pineal glands in the brain
Thyroid and parathyroid glands in the neck
Thymus in the upper chest
Adrenal glands above the kidneys
Pancreas near the stomach
Ovaries or testes in the reproductive region
The pituitary gland is called the master gland
The pituitary gland is a small gland found at the base of the brain. It is about the size of a pea, but it controls many other endocrine glands.
It is called the master gland because it releases hormones that control other glands, such as:
Thyroid gland
Adrenal glands
Ovaries
Testes
The pituitary gland is controlled by a part of the brain called the hypothalamus. So, the pituitary is the master gland, but the hypothalamus acts like its manager.
Important pituitary hormones
Pituitary hormone | Main function |
Growth hormone | Helps bones and muscles grow |
TSH | Stimulates the thyroid gland |
ACTH | Stimulates the adrenal glands |
FSH | Helps in egg and sperm formation |
LH | Helps in reproductive hormone production |
ADH | Helps kidneys save water |
Prolactin | Helps in milk production after childbirth |
Growth hormone disorders
Growth hormone helps normal body growth during childhood.
If too little growth hormone is produced in childhood, it may lead to very short height. If too much growth hormone is produced in childhood, it may lead to unusual excessive growth.
In adults, too much growth hormone may cause enlargement of hands, feet, and facial bones. This condition is known as acromegaly.
Thyroid and parathyroid glands
The thyroid gland is a butterfly-shaped gland in the front of the neck. It produces thyroxine, a hormone that controls metabolism.
Metabolism means all the chemical activities by which the body gets and uses energy.
Functions of thyroxine
Thyroxine helps to control:
How fast the body uses food
Body temperature
Heartbeat
Growth and brain development in children
Energy levels
The thyroid gland needs iodine to make thyroxine. Iodine is found in iodised salt, seafood, dairy products, and some other foods.
Hypothyroidism
Hypothyroidism happens when the thyroid gland produces too little thyroxine.
Common signs may include:
Feeling tired
Weight gain
Feeling cold
Slow heartbeat
Dry skin
Slow growth in children
Hyperthyroidism
Hyperthyroidism happens when the thyroid gland produces too much thyroxine.
Common signs may include:
Weight loss
Fast heartbeat
Feeling hot
Sweating
Nervousness
Shaky hands
Parathyroid glands
The parathyroid glands are four tiny glands behind the thyroid gland. They produce parathyroid hormone.
Parathyroid hormone controls calcium levels in the blood. Calcium is needed for:
Strong bones and teeth
Muscle contraction
Nerve function
Blood clotting
Adrenal glands help the body face stress
The adrenal gland is found on top of each kidney. There are two adrenal glands, one above each kidney.
The adrenal glands produce hormones such as adrenaline, cortisol, and aldosterone.
Adrenaline
Adrenaline prepares the body for emergency action.
When you are scared before going on stage or when a fast ball comes towards you in cricket, adrenaline may increase.
It causes:
Faster heartbeat
Faster breathing
More glucose release into blood
More blood flow to muscles
Wider pupils
Cortisol
Cortisol helps the body respond to longer periods of stress. It also helps control metabolism and inflammation.
Aldosterone
Aldosterone helps maintain salt and water balance. This supports normal blood pressure.
Pancreas and blood sugar regulation
The pancreas lies behind the stomach. It plays a key role in digestion and blood sugar control.
As an endocrine gland, it has special cell groups called islets. These cells release two important hormones:
Insulin
Glucagon
Insulin lowers blood sugar
After eating rice, chapati, fruits, or sweets, glucose enters the blood. When blood sugar rises, the pancreas releases insulin.
Insulin helps:
Body cells take in glucose
Liver store glucose as glycogen
Blood sugar return to normal
Glucagon raises blood sugar
When you have not eaten for some time, blood sugar may fall. The pancreas releases glucagon.
Glucagon helps:
Liver break down glycogen into glucose
Glucose enter the blood
Blood sugar return to normal
Blood sugar balance in simple words
Situation | Hormone released | What happens |
Blood sugar is high after a meal | Insulin | Cells take in glucose and blood sugar falls |
Blood sugar is low between meals | Glucagon | Liver releases glucose and blood sugar rises |
Diabetes
Diabetes is a common hormonal disorder related to insulin.
In diabetes, the body either does not make enough insulin or cannot use insulin properly. This causes high blood sugar.
Common signs may include:
Frequent urination
Feeling very thirsty
Feeling tired
Slow wound healing
Unexplained weight changes
A doctor can diagnose and manage diabetes through tests, medicines, food planning, and lifestyle support.
Pineal gland and sleep
The pineal gland is a small gland in the brain. It produces melatonin.
Melatonin helps control the sleep and wake cycle.
When it becomes dark, melatonin level usually increases. This makes the body feel sleepy. Bright light, especially from screens at night, can disturb melatonin release and affect sleep.
Good sleep habits help the pineal gland work well:
Sleep and wake up at regular times
Avoid screens close to bedtime
Keep the room dark and quiet
Avoid too much caffeine from tea, coffee, or cola
Thymus gland and immunity
The thymus gland is found in the upper chest, behind the breastbone. It is more active in children and becomes smaller after puberty.
The thymus produces thymosin. This hormone helps certain white blood cells, called T-cells, develop properly.
T-cells are important for immunity. They help the body fight infections.
Ovaries and testes as endocrine glands
The ovaries and testes are reproductive organs, but they also work as endocrine glands because they produce hormones.
Ovaries
Ovaries are found in the lower abdomen in females. They produce oestrogen and progesterone.
These hormones help in:
Development of female secondary sexual characters
Menstrual cycle
Preparation of the uterus for pregnancy
Breast development
Wider hips during puberty
Testes
Testes are found in the scrotum in males. They produce testosterone.
Testosterone helps in:
Development of male secondary sexual characters
Growth of facial and body hair
Deepening of voice
Muscle development
Sperm production
Puberty changes happen because of human hormones released by endocrine glands.
Hormones and their functions
The table below gives a quick view of important hormones and their functions.
Hormone | Gland | Main function |
Growth hormone | Pituitary | Helps body growth |
Thyroxine | Thyroid | Controls metabolism |
Parathyroid hormone | Parathyroid | Controls calcium level |
Adrenaline | Adrenal | Prepares body for emergency |
Cortisol | Adrenal | Helps in stress response |
Aldosterone | Adrenal | Controls salt and water balance |
Insulin | Pancreas | Lowers blood sugar |
Glucagon | Pancreas | Raises blood sugar |
Melatonin | Pineal | Controls sleep cycle |
Thymosin | Thymus | Helps immune cell development |
Oestrogen | Ovaries | Controls female reproductive changes |
Progesterone | Ovaries | Helps menstrual cycle and pregnancy preparation |
Testosterone | Testes | Controls male reproductive changes |
ADH | Pituitary | Helps kidneys retain water |
Role of hormones in body functions
Hormones affect many everyday activities. You may not see them, but they are working all the time.
Growth
Growth hormone, thyroxine, insulin, and sex hormones all support growth.
For example, during puberty, hormones cause:
Increase in height
Growth of body hair
Change in voice
Development of reproductive organs
Metabolism
Thyroxine controls how quickly the body uses energy.
If thyroxine is too low, a person may feel tired and gain weight. If it is too high, a person may lose weight and feel restless.
Stress
Adrenaline and cortisol help the body respond to stress.
Short-term stress can help during emergencies. Long-term stress can disturb sleep, appetite, mood, and health.
Sleep
Melatonin helps the body know when to sleep and wake up. Too much screen time at night can confuse the body’s sleep signals.
Blood sugar
Insulin and glucagon work like opposite partners. One lowers blood sugar, and the other raises it.
Reproduction
Oestrogen, progesterone, testosterone, FSH, and LH control puberty, reproductive development, menstrual cycle, sperm production, and pregnancy-related changes.
How the nervous and endocrine systems work together
The nervous system and endocrine system both help the body respond to changes.
Feature | Nervous system | Endocrine system |
Message type | Electrical impulses and chemicals | Hormones |
Pathway | Nerves | Blood |
Speed | Very fast | Slower |
Effect duration | Usually short | Usually longer |
Example | Pulling hand away from hot object | Growth during puberty |
These two systems often work together.
For example, when you see a snake:
Eyes send information to the brain.
Brain recognises danger.
Nervous system sends quick signals.
Adrenal glands release adrenaline.
Heartbeat and breathing increase.
The nervous system gives a fast response. The endocrine system supports the response through hormones.
Feedback mechanisms keep hormones balanced
The body must keep hormone levels balanced. Too much or too little hormone can cause problems.
A feedback mechanism is a control system that checks hormone levels and adjusts them.
The most common type is negative feedback.
Example of blood sugar feedback
Blood sugar rises after food.
Pancreas releases insulin.
Blood sugar falls to normal.
Pancreas reduces insulin release.
If blood sugar becomes low:
Pancreas releases glucagon.
Liver releases glucose.
Blood sugar rises to normal.
Pancreas reduces glucagon release.
Example of thyroid feedback
Pituitary gland releases TSH.
TSH stimulates thyroid gland.
Thyroid releases thyroxine.
When thyroxine is enough, the brain and pituitary reduce TSH release.
This helps maintain hormonal balance.
Common hormonal disorders
Hormonal disorders happen when glands produce too much or too little hormone, or when the body cannot respond properly to a hormone.
Disorder | Main hormone or gland involved | Simple explanation |
Diabetes | Insulin, pancreas | Blood sugar stays too high |
Hypothyroidism | Thyroxine, thyroid | Metabolism becomes slow |
Hyperthyroidism | Thyroxine, thyroid | Metabolism becomes too fast |
Growth hormone deficiency | Growth hormone, pituitary | Slow or reduced growth in children |
Excess growth hormone | Growth hormone, pituitary | Unusual excessive growth in children |
Calcium imbalance | Parathyroid hormone | Calcium level becomes too high or too low |
Many disorders can be managed well with medical care. Never self-diagnose based only on symptoms.
Healthy habits that support the endocrine system
Healthy habits cannot prevent every hormonal disorder, but they support normal body functions.
Helpful habits include:
Eat a balanced diet with cereals, pulses, vegetables, fruits, milk or curd, nuts, and enough protein.
Use iodised salt in normal amounts.
Stay physically active through walking, cycling, sports, yoga, or play.
Sleep for enough hours and keep a regular sleep routine.
Drink enough water.
Manage stress with breathing exercises, hobbies, prayer, music, or talking to trusted people.
Avoid tobacco, alcohol, and harmful substances.
Limit junk food, sugary drinks, and too much packaged food.
Follow medical advice for thyroid problems, diabetes, or growth concerns.
Did you know facts
The pituitary gland is tiny, but it controls many other glands.
Hormones travel in the blood, but they act only on cells with the correct receptors.
The pancreas can work as both an endocrine and exocrine gland.
Adrenaline can make your heart beat faster within seconds.
The thymus is larger and more active in children than in adults.
Melatonin is linked with darkness and sleep.
Thyroxine needs iodine for its production.
Insulin and glucagon work in opposite ways to balance blood sugar.
Common misconceptions about hormones
Misconception | Correct idea |
Hormones are only related to puberty | Hormones control growth, sleep, stress, blood sugar, metabolism, and more |
All glands are endocrine glands | Some glands are exocrine, such as sweat and salivary glands |
The pituitary gland works alone | It is controlled by the hypothalamus |
Insulin gives energy directly | Insulin helps cells take in glucose, which is used for energy |
Adrenaline is always harmful | It is useful in emergencies, but long-term stress can be harmful |
Only adults get hormonal disorders | Children and teenagers can also have hormonal problems |
Exam tips for endocrine system questions
Use these tips while preparing endocrine system for students topics:
Learn gland, hormone, and function together.
Practise labelled diagrams of endocrine glands.
Remember that endocrine glands are ductless.
Write insulin and glucagon as opposite hormones.
Mention that the pituitary is called the master gland because it controls other glands.
For thyroid answers, include metabolism and iodine.
For adrenal glands, connect adrenaline with fight or flight.
In long answers, use examples from daily life.
Quick revision notes
The endocrine system is made of ductless glands.
Endocrine glands release hormones directly into the blood.
Hormones are chemical messengers.
The pituitary gland is called the master gland.
Thyroxine controls metabolism.
Parathyroid hormone controls calcium level.
Adrenaline prepares the body for emergencies.
Insulin lowers blood sugar.
Glucagon raises blood sugar.
Melatonin controls sleep cycle.
Thymosin helps immune system development.
Oestrogen, progesterone, and testosterone control reproductive changes.
Negative feedback helps maintain hormonal balance.
Frequently asked questions
1. What is the endocrine system?
The endocrine system is a group of glands that produce hormones and release them directly into the blood.
2. What are hormones?
Hormones are chemical messengers that control body activities such as growth, metabolism, stress, sleep, and reproduction.
3. Why is the pituitary gland called the master gland?
The pituitary gland is called the master gland because it releases hormones that control other endocrine glands.
4. Which hormone controls blood sugar?
Insulin and glucagon control blood sugar. Insulin lowers blood sugar, while glucagon raises it.
5. Which gland produces thyroxine?
The thyroid gland produces thyroxine.
6. What is the function of adrenaline?
Adrenaline prepares the body for emergency action by increasing heartbeat, breathing, and energy release.
7. What is the difference between endocrine and exocrine glands?
Endocrine glands release hormones into blood. Exocrine glands release substances through ducts.
8. Which hormone helps us sleep?
Melatonin, produced by the pineal gland, helps control the sleep and wake cycle.
9. What happens in diabetes?
In diabetes, the body does not make enough insulin or cannot use insulin properly, so blood sugar remains high.
10. Which hormones are related to puberty?
Oestrogen, progesterone, testosterone, FSH, and LH are important during puberty.
20 solved questions
1. Define endocrine gland.
An endocrine gland is a ductless gland that releases hormones directly into the blood.
2. What are hormones?
Hormones are chemical messengers that regulate body activities.
3. Name the master gland.
The pituitary gland is called the master gland.
4. Why is the pituitary gland important?
It controls growth and also controls other glands such as the thyroid, adrenal glands, ovaries, and testes.
5. Name the hormone produced by the thyroid gland.
The thyroid gland produces thyroxine.
6. What is the role of thyroxine?
Thyroxine controls metabolism, growth, and body temperature.
7. Which mineral is needed to make thyroxine?
Iodine is needed to make thyroxine.
8. Name two hormones produced by the pancreas.
The pancreas produces insulin and glucagon.
9. What is the function of insulin?
Insulin lowers blood sugar by helping cells take in glucose.
10. What is the function of glucagon?
Glucagon raises blood sugar by helping the liver release glucose.
11. Where are adrenal glands located?
Adrenal glands are located above the kidneys.
12. What does adrenaline do?
Adrenaline prepares the body for emergencies.
13. Name the hormone of the pineal gland.
The pineal gland produces melatonin.
14. What is the function of melatonin?
Melatonin controls the sleep and wake cycle.
15. What does the thymus gland do?
The thymus gland produces thymosin, which helps immune cells develop.
16. Name two hormones produced by ovaries.
Ovaries produce oestrogen and progesterone.
17. Name the hormone produced by testes.
Testes produce testosterone.
18. What is negative feedback?
Negative feedback is a control method in which the body reduces or increases hormone release to keep levels normal.
19. Give one example of an exocrine gland.
A salivary gland is an exocrine gland.
20. What is diabetes?
Diabetes is a condition in which blood sugar remains high due to problems with insulin production or insulin action.
25 practice questions
What is the endocrine system?
What are target cells?
Why are endocrine glands called ductless glands?
Give two examples of endocrine glands.
Give two examples of exocrine glands.
Which gland is called the master gland?
Name one hormone released by the pituitary gland.
What is the function of growth hormone?
Where is the thyroid gland located?
10. What is hypothyroidism?
11. What is hyperthyroidism?
12. What do parathyroid glands control?
13. Where are adrenal glands found?
14. What is fight or flight response?
15. Name two hormones of the pancreas.
16. How does insulin affect blood sugar?
17. How does glucagon affect blood sugar?
18. What is the function of melatonin?
19. Why is the thymus important in children?
20. Name two hormones produced by ovaries.
21. What is the main hormone produced by testes?
22. How do the nervous and endocrine systems differ in speed?
23. What is negative feedback?
24. Write any two healthy habits that support the endocrine system.
25. Draw and label the major endocrine glands in the human body.
Answer key
A system of glands that release hormones into blood.
Cells that have receptors for a particular hormone.
Because they do not have ducts.
Pituitary gland and thyroid gland.
Sweat gland and salivary gland.
Pituitary gland.
Growth hormone, TSH, ACTH, FSH, LH, ADH, or prolactin.
It helps bones and muscles grow.
In the front of the neck.
10. A condition with too little thyroxine.
11. A condition with too much thyroxine.
12. Calcium level in blood.
13. Above the kidneys.
14. The body’s emergency response to danger.
15. Insulin and glucagon.
16. It lowers blood sugar.
17. It raises blood sugar.
18. It controls the sleep and wake cycle.
19. It helps T-cells develop for immunity.
20. Oestrogen and progesterone.
21. Testosterone.
22. The nervous system is faster, while the endocrine system is slower but longer-lasting.
23. A control system that keeps hormone levels balanced.
24. Balanced diet, regular exercise, good sleep, stress control, enough water, or avoiding harmful substances.
25. The diagram should include pituitary, thyroid, parathyroid, thymus, adrenal glands, pancreas, ovaries or testes, and pineal gland.
Conclusion
The endocrine system may seem difficult at first because it includes many glands and hormones. The easiest way to learn it is to connect each gland with its hormone and function.
Remember these key ideas:
Endocrine glands are ductless glands.
Hormones are chemical messengers.
The pituitary gland controls many other glands.
Thyroid hormone controls metabolism.
Adrenaline helps during emergencies.
Insulin and glucagon balance blood sugar.
Hormones help in growth, sleep, stress response, and reproduction.
Feedback mechanisms keep hormone levels balanced.
If you can explain these points with examples and diagrams, you will be well prepared for school exams and class discussions on human hormones.
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