Endocrine System & Hormones — the Gland-Hormone Master Table

Why This Chapter Matters

The gland-hormone table in this chapter alone is worth 2-3 direct marks in almost every SSC CGL, CHSL, MTS, and RRB NTPC General Awareness paper, and it comes back again in police and banking GA sections too. Questions here are blunt and factual: which gland secretes insulin, what does a deficiency of growth hormone in childhood cause, which is the "master gland." There is no reasoning required, only recall, which means this is pure, guaranteed score if you memorise the table properly.

The single biggest mistake aspirants make with this topic is mixing up the pituitary gland with the master gland it controls versus the thyroid, and confusing hormone deficiency diseases that sound similar (dwarfism vs cretinism, goitre vs Graves' disease). Another common trap is forgetting that some organs, like the pancreas and the ovaries/testes, do double duty as both digestive/reproductive organs and endocrine glands. You will see this exact confusion tested directly, so pay close attention to the "exam trap" notes as you go.

What Is the Endocrine System

Your body runs two communication networks side by side. The nervous system sends messages like a phone call: instant, wired, and short-lived. The endocrine system sends messages like a postal service: it releases chemical messengers called hormones into the bloodstream, and they travel slowly to reach target organs far away, producing effects that last minutes, hours, or even years.

Hormones are chemical substances produced by endocrine glands (also called ductless glands, because they release their secretion directly into blood rather than through a tube). This is different from exocrine glands like sweat glands and salivary glands, which release their product through a duct onto a surface.

Exam trap: Do not confuse endocrine (ductless, hormone into blood) with exocrine (has a duct, secretion onto a surface). SSC has directly asked "which of these is a ductless gland" more than once.

Think of the endocrine system as the body's WhatsApp broadcast list. One gland "posts" a hormone into the bloodstream, and only the organs that have the matching "receptor" (the ones who follow that broadcast) respond to it. Everyone else in the bloodstream just lets the message pass by unread.

The Master Table: Glands and Their Hormones

This is the table to know cold. Read it left to right multiple times until you can cover the right two columns and reconstruct them from the gland name alone.

Gland	Location	Key Hormone(s)	Main Function
Hypothalamus	Base of brain	Releasing & inhibiting hormones (e.g., TRH, GnRH)	Controls the pituitary; bridges nervous and endocrine systems
Pituitary (Master gland)	Base of brain, below hypothalamus	GH (growth hormone), TSH, ACTH, FSH, LH, Prolactin, Oxytocin, ADH (Vasopressin)	Controls growth and regulates most other endocrine glands
Pineal gland	Middle of brain	Melatonin	Regulates sleep-wake cycle (body clock)
Thyroid	Front of neck, near voice box	Thyroxine (T4), Triiodothyronine (T3), Calcitonin	Controls metabolic rate (T3/T4); calcitonin lowers blood calcium
Parathyroid (4 small glands)	Behind thyroid	Parathormone (PTH)	Raises blood calcium level
Thymus	Upper chest, behind sternum	Thymosin	Develops T-lymphocytes; active mainly in childhood
Adrenal (Suprarenal)	On top of each kidney	Cortex: Cortisol, Aldosterone — Medulla: Adrenaline (Epinephrine), Noradrenaline	Stress response, blood pressure and salt-water balance, metabolism
Pancreas (Islets of Langerhans)	Behind stomach	Insulin (beta cells), Glucagon (alpha cells)	Insulin lowers blood sugar, glucagon raises it
Testes	Scrotum (male)	Testosterone	Male secondary sexual characteristics, sperm production
Ovaries	Pelvis (female)	Estrogen, Progesterone	Female secondary sexual characteristics, menstrual cycle, pregnancy support

Exam trap: The pancreas is both an exocrine gland (secretes digestive enzymes through a duct into the small intestine) and an endocrine gland (Islets of Langerhans secrete insulin and glucagon directly into blood). SSC loves asking "which gland is both exocrine and endocrine" — the answer is always pancreas.

Memory hook: For the pituitary's hormone list, picture it as the "government secretariat" of the body, issuing orders to every department: Growth department (GH), Thyroid department (TSH), Adrenal department (ACTH), reproductive departments (FSH, LH), milk department (Prolactin), and its own direct action staff for water (ADH) and childbirth (Oxytocin) — a secretariat that both manages other departments and runs a couple of its own.

The Pituitary: Why It Is Called the Master Gland

The pituitary gland, roughly the size of a pea, sits at the base of your brain and is called the master gland because most of its hormones control other endocrine glands rather than acting directly. TSH tells the thyroid how much thyroxine to make. ACTH tells the adrenal cortex how much cortisol to produce. FSH and LH direct the ovaries and testes.

But the pituitary itself takes orders from the hypothalamus, a small region of the brain just above it, which releases its own hormones to switch pituitary hormones on or off. So the real chain of command is hypothalamus, then pituitary, then the target gland. Think of the hypothalamus as the CEO, the pituitary as the general manager who is called "master gland" because everyone below reports to them, and the individual glands (thyroid, adrenal, gonads) as the department heads who actually do the work.

Exam trap: Students often think the pituitary is the "boss of the boss" with nobody controlling it. It is not. The hypothalamus sits above the pituitary in the chain of command, even though the pituitary is the one labelled "master gland" in textbooks because of how many other glands it directs.

The pituitary has two lobes with genuinely different jobs. The anterior pituitary makes GH, TSH, ACTH, FSH, LH, and prolactin on its own. The posterior pituitary does not manufacture hormones itself; it only stores and releases oxytocin and ADH (antidiuretic hormone), which are actually made in the hypothalamus and travel down a short nerve tract to be released from the posterior pituitary.

Growth Hormone and the Height Story

Growth hormone (GH), from the anterior pituitary, controls the growth of bones and muscles, mainly during childhood and adolescence. Exams test its abnormal levels heavily, because the resulting conditions are visually memorable and easy to confuse with each other.

• Dwarfism: GH deficiency in childhood, before the growth plates in long bones close. Result: abnormally short stature with normal body proportions.
• Gigantism: GH excess in childhood. Result: abnormally tall stature.
• Acromegaly: GH excess in adulthood, after growth plates have already closed, so the person cannot grow taller. Instead, bones in the hands, feet, and face thicken and enlarge.

Exam trap: Gigantism and acromegaly are both caused by too much growth hormone, but the timing decides the outcome. Too much GH before growth plates close gives you a giant. Too much GH after they close gives you acromegaly, not extra height. This exact "before vs after growth plates close" distinction is a favourite SSC question.

Memory hook: Picture growth plates in long bones like a shop that shuts its shutters at closing time. If the shutters (growth plates) are still open when extra GH arrives, the whole shop (skeleton) expands, giving you a giant. If the shutters have already come down (adulthood), the extra GH can only push at the door frame and window edges, thickening the hands, feet, and jaw. That is acromegaly.

Thyroid, Iodine, and Metabolism

The thyroid gland wraps around your windpipe in the front of the neck and produces thyroxine (T4) and triiodothyronine (T3), both built using iodine from your diet. These hormones set your basal metabolic rate, essentially how fast your body burns energy at rest. Too little thyroxine and everything slows down: low energy, weight gain, sluggish thinking. Too much and everything speeds up: high energy, weight loss, restlessness, a racing heart.

Iodine deficiency is the classic exam story here. Without enough dietary iodine, the thyroid cannot make enough thyroxine. The pituitary senses low thyroxine and pumps out more TSH to compel the thyroid to work harder, and this overstimulation causes the thyroid tissue itself to swell. That visible swelling in the neck is called goitre.

Exam trap: Do not confuse goitre (a swelling caused by iodine-deficiency hypothyroidism, treatable with iodised salt) with Graves' disease (an autoimmune condition causing hyperthyroidism, i.e., excess thyroid hormone, sometimes with bulging eyes). Goitre is linked to too little iodine and low thyroid output; Graves' disease is linked to an overactive thyroid.

Real-world grounding: This is exactly why Indian government policy mandates iodised salt; you have almost certainly seen "iodised" printed on your kitchen salt packet. That single word on a salt packet single-handedly reduced goitre cases across India, and it is a genuinely good example of a public-health fact you might see in a GS question tied to biology.

If thyroxine deficiency happens in a newborn or young child rather than an adult, the result is far more serious: cretinism, marked by stunted physical growth and impaired mental development. In adults, severe long-term hypothyroidism instead causes myxoedema, marked by dry skin, puffiness, weight gain, and mental slowness, without the developmental damage seen in cretinism.

The thyroid's third hormone, calcitonin, is often forgotten by aspirants who only remember T3/T4. Calcitonin lowers blood calcium levels by pushing calcium into bones, working in balance against the parathyroid hormone described next.

Parathyroid and Calcium Balance

Behind the thyroid sit four tiny parathyroid glands, easy to overlook but a frequent exam topic because their job pairs neatly with the thyroid's calcitonin in a classic "opposite hormones" question. Parathormone (PTH) raises blood calcium levels, pulling calcium out of bone and into blood when levels run low, which is the opposite direction to calcitonin.

Memory hook: Para-thormone pumps calcium up; calci-tonin tones calcium down. Same letters "para" sound like "pa-raise," and "calci-tonin" rhymes with "tone it down."

Adrenal Glands: Your Body's Emergency Response Team

Sitting like little caps on top of each kidney, the adrenal glands have two distinct regions doing two very different jobs, and exams test both separately.

The adrenal medulla (inner region) releases adrenaline (epinephrine) and noradrenaline (norepinephrine) during sudden stress. This is the classic "fight or flight" response: heart rate shoots up, blood pressure rises, pupils dilate, blood is diverted to muscles, and blood sugar is released for quick energy.

Real-world grounding: You have felt this yourself, the jolt when a bus suddenly brakes hard in front of you, or the second before you walk into an exam hall. That immediate racing heartbeat and alertness is adrenaline at work, released within seconds.

The adrenal cortex (outer region) releases steroid hormones on a slower, longer timescale. Cortisol manages the body's response to prolonged stress and regulates metabolism of glucose, fat, and protein. Aldosterone manages salt and water balance by controlling how much sodium the kidneys retain, which directly affects blood pressure.

Exam trap: Adrenaline acts in seconds for an immediate physical threat; cortisol acts over hours or days for sustained stress. If a question describes a slow, chronic response involving blood sugar and immune suppression, it points to cortisol, not adrenaline.

Pancreas: Insulin, Glucagon, and Diabetes

The pancreas contains clusters of hormone-producing cells called the Islets of Langerhans, named after the scientist who discovered them. Within these islets, beta cells secrete insulin and alpha cells secrete glucagon, and the two work like a seesaw to keep blood glucose steady.

After you eat and blood sugar rises, insulin signals cells to absorb glucose from the blood and store the extra as glycogen in the liver, bringing blood sugar back down. Between meals, when blood sugar drops, glucagon signals the liver to break glycogen back down into glucose and release it into blood, bringing sugar back up.

Analogy: Think of blood glucose like water level in an overhead tank. Insulin is the outlet valve that drains excess water into a storage tank (glycogen in the liver) when the level runs high. Glucagon is the pump that refills the overhead tank from storage when the level runs low. A healthy pancreas keeps adjusting both valve and pump automatically so the tank never overflows or runs dry.

Diabetes mellitus results when this system fails. Type 1 diabetes happens when the pancreas produces too little or no insulin, usually starting in childhood, and requires insulin injections for life. Type 2 diabetes, far more common and linked to lifestyle and obesity, happens when the body's cells stop responding properly to insulin even though the pancreas still makes it, a state called insulin resistance.

Exam trap: "Diabetes insipidus" and "diabetes mellitus" sound alike but are unrelated conditions. Diabetes mellitus is a blood-sugar/insulin disorder from the pancreas. Diabetes insipidus is caused by a deficiency of ADH from the pituitary and causes excessive dilute urination without affecting blood sugar at all. SSC has tested this exact word trap.

Reproductive Hormones in Brief

The testes produce testosterone, responsible for male secondary sexual characteristics such as facial hair, deepened voice, and muscle development, along with sperm production. The ovaries produce estrogen and progesterone, which drive female secondary sexual characteristics, regulate the menstrual cycle, and maintain pregnancy. This chapter covers them only at the hormone-naming level; the reproductive system itself, including the menstrual cycle in detail, is covered in Chapter 8.

Other Hormones Worth Knowing

A few smaller glands round out the picture and occasionally show up as standalone questions.

The pineal gland, deep in the brain, secretes melatonin, which regulates your sleep-wake cycle in response to light and darkness. Melatonin rises in the dark, which is why bright screens at night (which suppress it) make falling asleep harder, a genuinely useful fact beyond the exam too.

The thymus, located behind the breastbone, secretes thymosin and is where T-lymphocytes (a key immune cell) mature. It is largest and most active in childhood and shrinks with age, an unusual pattern worth remembering since most glands do not shrink as you grow up.

The Feedback Loop Concept

Almost every hormone in the body is controlled by a negative feedback loop, the single most important concept-level idea in this chapter, and it explains why the system rarely stays "stuck" at too high or too low a level. In simple terms, when a hormone's effect reaches the desired level, that outcome itself signals the gland to stop producing more, the same way a room thermostat cuts off the heater once the target temperature is reached.

Take thyroxine as the clearest example. Low blood thyroxine is detected by the hypothalamus and pituitary, which respond by releasing TRH and TSH to push the thyroid to make more thyroxine. As thyroxine levels climb back to normal, that rise itself signals the hypothalamus and pituitary to reduce TRH and TSH output, so thyroxine production slows down again. This loop runs continuously and automatically, without you ever consciously noticing it, which is exactly why a permanent malfunction anywhere in the loop (not enough iodine to make thyroxine, a damaged pituitary, or a diseased thyroid) can throw the whole system off for years.

Exam trap: This is called negative feedback specifically because the response opposes (negates) the original change, not because it is a "bad" or "harmful" loop. Some students wrongly assume "negative" means something has gone wrong.

Quick Revision — One-Line Facts

• The pituitary gland is called the master gland because it controls most other endocrine glands.
• The hypothalamus controls the pituitary itself, sitting above it in the chain of command.
• Insulin is secreted by the beta cells of the Islets of Langerhans in the pancreas.
• Glucagon, from alpha cells of the pancreas, raises blood glucose; insulin lowers it.
• The pancreas is both an exocrine and endocrine gland.
• Thyroxine (T3/T4) from the thyroid requires iodine and controls metabolic rate.
• Goitre results from iodine-deficiency hypothyroidism causing thyroid gland swelling.
• Cretinism is childhood thyroxine deficiency; it stunts both physical and mental growth.
• Myxoedema is severe hypothyroidism in adults.
• Graves' disease is autoimmune hyperthyroidism, unrelated to iodine deficiency.
• Calcitonin, from the thyroid, lowers blood calcium.
• Parathormone (PTH), from the parathyroid glands, raises blood calcium.
• Growth hormone (GH) deficiency in childhood causes dwarfism.
• GH excess in childhood causes gigantism; excess in adulthood causes acromegaly.
• Adrenaline and noradrenaline, from the adrenal medulla, drive the "fight or flight" response.
• Cortisol, from the adrenal cortex, manages long-term stress and metabolism.
• Aldosterone, from the adrenal cortex, regulates sodium and water balance, affecting blood pressure.
• Diabetes mellitus is caused by insulin deficiency or resistance; diabetes insipidus is caused by ADH deficiency.
• Type 1 diabetes: little or no insulin production, usually from childhood.
• Type 2 diabetes: insulin resistance, linked to lifestyle and obesity.
• Testosterone is secreted by the testes; estrogen and progesterone by the ovaries.
• Melatonin, from the pineal gland, regulates the sleep-wake cycle.
• Thymosin, from the thymus, helps develop T-lymphocytes and is most active in childhood.
• Oxytocin and ADH are released by the posterior pituitary but manufactured in the hypothalamus.
• Prolactin stimulates milk production in mammary glands.
• FSH and LH regulate the reproductive glands (testes and ovaries).
• ACTH from the pituitary stimulates the adrenal cortex to release cortisol.
• TSH from the pituitary stimulates the thyroid to release thyroxine.
• Endocrine glands are ductless; exocrine glands release secretions through a duct.
• Hormone regulation mostly runs through negative feedback loops.
• Excess ADH deficiency causes diabetes insipidus, marked by excessive dilute urination.

Memory Tables

Table 1: Deficiency and Excess Disease Pairs

Hormone	Deficiency Condition	Excess Condition
Growth hormone (childhood)	Dwarfism	Gigantism
Growth hormone (adulthood)	—	Acromegaly
Thyroxine (childhood)	Cretinism	—
Thyroxine (adulthood)	Myxoedema	Graves' disease (hyperthyroidism)
Insulin	Diabetes mellitus	—
ADH	Diabetes insipidus	—
Parathormone	Low blood calcium (tetany)	High blood calcium

Table 2: Gland Location and Nickname Quick-Match

Gland	One-word location cue	Common nickname/identity
Pituitary	Base of brain	Master gland
Hypothalamus	Above pituitary	Controller of the master gland
Thyroid	Neck (front)	Metabolism regulator, needs iodine
Parathyroid	Behind thyroid	Calcium raiser
Adrenal	Atop kidneys	Stress response glands
Pancreas	Behind stomach	Blood sugar regulator, dual gland
Pineal	Deep in brain	Body clock gland
Thymus	Behind breastbone	Childhood immunity gland
Testes/Ovaries	Reproductive organs	Sex hormone glands

Practice MCQs

Q1. Which gland is known as the "master gland" of the human body? (a) Thyroid (b) Pituitary (c) Adrenal (d) Pancreas

Q2. Insulin is secreted by which cells of the pancreas? (a) Alpha cells (b) Beta cells (c) Delta cells (d) Acinar cells

Q3. Which mineral is essential for the synthesis of thyroxine? (a) Iron (b) Calcium (c) Iodine (d) Zinc

Q4. Adrenaline is secreted by which part of the adrenal gland? (a) Adrenal cortex (b) Adrenal medulla (c) Both equally (d) Neither

Q5. Which hormone regulates the sleep-wake cycle? (a) Melatonin (b) Thymosin (c) Prolactin (d) Cortisol

Q6. Which gland is both an exocrine and an endocrine gland? (a) Thyroid (b) Adrenal (c) Pancreas (d) Pituitary

Q7. Growth hormone deficiency in childhood leads to which condition? (a) Gigantism (b) Acromegaly (c) Dwarfism (d) Goitre

Q8. Which condition results from iodine deficiency causing thyroid gland enlargement? (a) Cretinism (b) Goitre (c) Myxoedema (d) Graves' disease

Q9. Which pituitary hormone directly stimulates the adrenal cortex? (a) TSH (b) FSH (c) ACTH (d) LH

Q10. Which hormone raises blood calcium levels by acting on bone? (a) Calcitonin (b) Parathormone (c) Insulin (d) Cortisol

Q11. Excess growth hormone in an adult, after bone growth plates have closed, causes which condition? (a) Gigantism (b) Acromegaly (c) Dwarfism (d) Cretinism

Q12. Which gland releases oxytocin and ADH, although they are actually produced in the hypothalamus? (a) Anterior pituitary (b) Posterior pituitary (c) Thyroid (d) Pineal gland

Q13. Diabetes insipidus is primarily caused by a deficiency of which hormone? (a) Insulin (b) Glucagon (c) ADH (d) Cortisol

Q14. Which gland is largest and most active during childhood and shrinks with age? (a) Thyroid (b) Thymus (c) Pineal (d) Pancreas

Q15. Thyroxine deficiency from birth, causing stunted physical and mental growth, is called: (a) Myxoedema (b) Goitre (c) Cretinism (d) Acromegaly

Answer Key

Q	Answer	Reason
1	(b)	The pituitary is called the master gland because most of its hormones control other endocrine glands.
2	(b)	Beta cells of the Islets of Langerhans secrete insulin; alpha cells secrete glucagon instead.
3	(c)	Iodine is the essential building block of both T3 and T4; its lack causes goitre.
4	(b)	The adrenal medulla, the inner region, releases adrenaline and noradrenaline for fight-or-flight response.
5	(a)	Melatonin from the pineal gland rises in darkness and governs the sleep-wake cycle.
6	(c)	The pancreas secretes digestive enzymes via a duct (exocrine) and insulin/glucagon into blood (endocrine).
7	(c)	GH deficiency before growth plates close in childhood results in dwarfism with normal body proportions.
8	(b)	Low iodine forces the pituitary to raise TSH, overstimulating and enlarging the thyroid, seen as goitre.
9	(c)	ACTH (adrenocorticotropic hormone) specifically targets the adrenal cortex to release cortisol.
10	(b)	Parathormone pulls calcium from bone into blood, raising blood calcium; calcitonin does the opposite.
11	(b)	After growth plates close, extra GH cannot increase height, so it thickens hands, feet, and jaw instead: acromegaly.
12	(b)	The posterior pituitary stores and releases oxytocin and ADH, which are actually made in the hypothalamus.
13	(c)	Diabetes insipidus comes from ADH deficiency, causing excessive dilute urination, unrelated to blood sugar.
14	(b)	The thymus is most active in childhood, developing T-lymphocytes, and shrinks with age, unlike most glands.
15	(c)	Cretinism is childhood-onset thyroxine deficiency, damaging both physical and mental development; myxoedema is the adult version.