Which one of the following hormone is a steroid?

1. Introduction to the Endocrine System (basic)

The endocrine system is our body's internal chemical communication network. Unlike the nervous system, which sends rapid electrical signals through 'wires' (nerves), the endocrine system uses **hormones** — chemical messengers that travel through the bloodstream to reach distant organs. These hormones are produced by **endocrine glands**, which are often called 'ductless glands' because they release their secretions directly into the blood rather than through a tube Science, Class X (NCERT 2025 ed.), Control and Coordination, p. 111.
To understand how these hormones work, we must look at their chemical structure. Hormones are generally classified into two main groups:

• Peptide Hormones: These are made of amino acids (the building blocks of proteins). Examples include Insulin, Glucagon, and Oxytocin. Most peptide hormones end with the suffix '-in'.
• Steroid Hormones: These are lipophilic (fat-soluble) molecules synthesized from cholesterol. Examples include Cortisone, Testosterone, and Estrogen. They typically end in '-one' or '-ol'.

The role of these hormones is to maintain a state of balance and coordination in the body. For instance, the thyroid gland produces thyroxin to regulate your metabolism, while the hypothalamus acts as a master regulator, signaling the pituitary gland to release growth hormones when needed Science, Class X (NCERT 2025 ed.), Control and Coordination, p. 110. Whether it is the growth of a child or the complex changes during adolescence, hormones ensure that these processes happen at the right time and in the right place Science-Class VII, NCERT (Revised ed 2025), Adolescence: A Stage of Growth and Change, p. 84.

Feature	Peptide Hormones	Steroid Hormones
Chemical Base	Amino acids / Proteins	Cholesterol (Lipids)
Solubility	Water-soluble	Fat-soluble (Lipophilic)
Examples	Insulin, Oxytocin, Glucagon	Cortisone, Cortisol, Testosterone

Sources: Science, Class X (NCERT 2025 ed.), Control and Coordination, p.111; Science, Class X (NCERT 2025 ed.), Control and Coordination, p.109; Science, Class X (NCERT 2025 ed.), Control and Coordination, p.110; Science-Class VII, NCERT (Revised ed 2025), Adolescence: A Stage of Growth and Change, p.84

2. Major Endocrine Glands and Their Locations (basic)

In our body, coordination isn't just about electrical impulses from nerves; it involves a sophisticated chemical system called the Endocrine System. Unlike glands that have ducts (like sweat glands), endocrine glands are ductless. They secrete chemical messengers called hormones directly into the bloodstream to reach distant target organs. As noted in Science, Class X (NCERT 2025 ed.), Chapter 6, p.111, these hormones perform specific functions, often regulating growth and metabolism in carefully controlled places. At the very top of this hierarchy is the Hypothalamus, located in the brain. It acts as the command center, releasing factors that tell the Pituitary Gland (often called the 'Master Gland', located at the base of the brain) when to release its own hormones. For instance, the hypothalamus releases a growth hormone releasing factor to stimulate the pituitary Science, Class X (NCERT 2025 ed.), Chapter 6, p.110. Moving down to the neck, we find the Thyroid Gland, which requires iodine to produce thyroxin—a hormone vital for balancing our carbohydrate, protein, and fat metabolism. In the abdominal region, we find two crucial glands: the Pancreas, situated just below the stomach, and the Adrenal Glands, which sit like little caps on top of each kidney. While the pancreas regulates blood sugar levels, the adrenal glands are famous for the 'fight or flight' response. Finally, the Gonads (testes in males and ovaries in females) are located in the pelvic region and are responsible for reproductive development.

Endocrine Gland	Location in the Body	Key Function/Hormone Example
Hypothalamus	Brain	Regulates the Pituitary gland
Pituitary	Base of the Brain	Growth Hormone; Master regulator
Thyroid	Neck (Throat)	Thyroxin (Metabolism)
Adrenal	Above the Kidneys	Adrenaline (Stress response)
Pancreas	Abdomen (near stomach)	Insulin (Blood sugar control)

Sources: Science, Class X (NCERT 2025 ed.), Chapter 6: Control and Coordination, p.110; Science, Class X (NCERT 2025 ed.), Chapter 6: Control and Coordination, p.111

3. The Pancreas: A Dual Function Gland (intermediate)

The pancreas is a unique organ located behind the stomach that holds a special status in human physiology: it is a heterocrine gland (or dual-function gland). This means it operates both as an exocrine gland, secreting digestive enzymes through ducts into the small intestine, and as an endocrine gland, releasing hormones directly into the bloodstream to maintain internal balance. While many glands in our body do one or the other, the pancreas masters both to ensure our body is fueled and regulated simultaneously. In its endocrine capacity, the pancreas contains clusters of specialized cells known as the Islets of Langerhans. These cells act as the body's primary glucose sensors. As noted in Science, Class X (NCERT 2025 ed.), Control and Coordination, p. 110, the pancreas produces insulin, a vital hormone that helps regulate blood sugar levels. When we eat and our blood glucose rises, the pancreas detects this change and secretes insulin to help cells absorb that sugar for energy or storage. If the pancreas fails to produce enough insulin, sugar levels rise dangerously, leading to a condition known as diabetes. To keep our systems precise, the pancreas uses a sophisticated feedback mechanism. It doesn't just pump out hormones blindly; it constantly monitors the 'output' to adjust the 'input.' For instance, when blood sugar levels fall back to a normal range, the feedback loop signals the pancreatic cells to reduce insulin secretion Science, Class X (NCERT 2025 ed.), Control and Coordination, p. 111. This ensures that our internal environment remains stable, a state known as homeostasis.

Function Type	Secretory Product	Target Destination
Exocrine	Digestive Enzymes (e.g., Trypsin, Lipase)	Small Intestine (via ducts)
Endocrine	Hormones (Insulin and Glucagon)	Bloodstream (ductless)

Sources: Science, Class X (NCERT 2025 ed.), Control and Coordination, p.110; Science, Class X (NCERT 2025 ed.), Control and Coordination, p.111

4. Phytohormones: Plant Growth Regulators (intermediate)

In our study of biological coordination, we must understand that plants, lacking a nervous system, rely entirely on chemical signals to respond to their environment. These chemicals are known as Phytohormones or Plant Growth Regulators (PGRs). They are organic substances produced in minute quantities that control everything from a seed's germination to the falling of a withered leaf Environment, Shankar IAS Academy (ed 10th), Agriculture, p.370. We generally classify them into two functional groups: Growth Promoters and Growth Inhibitors.

The promoters include Auxins, Gibberellins, and Cytokinins. Auxins are synthesized at the tips of shoots and are responsible for phototropism—the process where a plant bends toward light. When light hits one side of a stem, auxin diffuses to the shady side, causing those cells to grow longer and forcing the stem to curve toward the light source Science, class X (NCERT 2025 ed.), Control and Coordination, p.108. Gibberellins work alongside auxins to aid stem elongation, while Cytokinins are the masters of cell division. You will naturally find cytokinins in high concentrations in areas of rapid growth, such as developing fruits and seeds Science, class X (NCERT 2025 ed.), Control and Coordination, p.108.

On the flip side, plants need a "braking system." Abscisic Acid (ABA) is the primary growth inhibitor; it signals the plant to stop growing and is responsible for the wilting of leaves—a crucial response during environmental stress Science, class X (NCERT 2025 ed.), Control and Coordination, p.108. Another fascinating regulator is Ethylene, a gaseous hormone. While it is essential for fruit ripening, an excess caused by environmental pollutants can lead to premature leaf fall and the shedding of floral buds Environment, Shankar IAS Academy (ed 10th), Environmental Pollution, p.69.

Hormone Group	Primary Examples	Key Functions
Growth Promoters	Auxins, Gibberellins, Cytokinins	Cell elongation, stem growth, rapid cell division in seeds/fruits.
Growth Inhibitors	Abscisic Acid (ABA), Ethylene	Inducing dormancy, leaf wilting, fruit ripening, and abscission (falling).

Sources: Science , class X (NCERT 2025 ed.), Control and Coordination, p.108; Environment, Shankar IAS Academy (ed 10th), Agriculture, p.370; Environment, Shankar IAS Academy (ed 10th), Environmental Pollution, p.69

5. Hormonal Feedback Mechanisms (intermediate)

In our body’s complex chemical communication system, precision is everything. Unlike a tap that stays open until you manually turn it off, our endocrine system uses feedback mechanisms to ensure hormones are secreted in exactly the right quantities at exactly the right time. Think of it like a smart thermostat: once the room reaches the desired temperature, the heater switches off automatically. In biological terms, this regulation prevents the over-secretion or under-secretion of hormones, which could otherwise lead to metabolic imbalances or growth disorders Science, Class X (NCERT 2025 ed.), Control and Coordination, p. 111. Most hormonal controls operate through Negative Feedback. In this loop, the effect produced by the hormone eventually acts as a signal to stop further secretion. A classic example is blood glucose regulation. When you eat a meal and your blood sugar rises, the cells of the pancreas detect this change and respond by producing insulin. As insulin helps cells absorb glucose, the blood sugar level falls. This drop is then detected by the pancreas, which reduces insulin secretion to prevent sugar levels from falling too low Science, Class X (NCERT 2025 ed.), Control and Coordination, p. 111. Another sophisticated layer of control involves the Hypothalamus, which acts as the master regulator. It monitors the levels of various hormones in the blood. For instance, if the level of Growth Hormone is low, the hypothalamus releases a 'releasing factor.' This factor travels to the pituitary gland, stimulating it to release more growth hormone. Once the levels are restored, the hypothalamus stops sending the 'releasing' signal, maintaining a perfect balance for the body's growth and metabolism Science, Class X (NCERT 2025 ed.), Control and Coordination, p. 110.

Sources: Science, Class X (NCERT 2025 ed.), Control and Coordination, p.110; Science, Class X (NCERT 2025 ed.), Control and Coordination, p.111

6. Nervous vs. Hormonal Coordination (intermediate)

In multicellular organisms like humans, coordination is achieved through two distinct yet complementary systems: the Nervous System and the Hormonal (Endocrine) System. While the nervous system uses electrical impulses for rapid, point-to-point communication, it has inherent limitations. Firstly, electrical impulses only reach cells physically connected by nervous tissue, meaning not every cell in the body is 'wired' Science, Class X (NCERT 2025 ed.), Control and Coordination, p.108. Secondly, once a neuron fires, it requires a 'reset' period to restore its chemical balance before it can transmit again, preventing continuous stimulation.

To overcome these gaps, the body uses chemical communication via hormones. These chemicals are secreted directly into the bloodstream and can reach every single cell in the body, regardless of whether a nerve is present Science, Class X (NCERT 2025 ed.), Control and Coordination, p.109. From a structural perspective, these chemical messengers are generally classified into two main groups: Peptides (like Insulin, Glucagon, and Oxytocin) and Steroids. Steroid hormones, such as Cortisone and Testosterone, are synthesized from cholesterol and are lipophilic (fat-soluble), often identified by the suffixes '-one' or '-ol'.

Feature	Nervous Coordination	Hormonal Coordination
Transmission	Electrical impulses via neurons	Chemical messengers via blood
Speed	Very rapid (milliseconds)	Relatively slow
Duration	Short-lived effects	Often long-lasting effects
Scope	Localized (specific muscles/glands)	Widespread (affects all target cells)

Sources: Science, Class X (NCERT 2025 ed.), Control and Coordination, p.101-111

7. Chemical Classification: Peptides vs. Steroids (exam-level)

Hormones are the body's chemical messengers, and their function is dictated by their chemical structure. Broadly, they are classified into two major structural groups: Peptide hormones and Steroid hormones. This classification is vital because it determines how a hormone travels through the bloodstream and how it interacts with its target cells.

Steroid hormones are lipophilic (fat-soluble) molecules derived from cholesterol. In the human body, they are primarily synthesized in the adrenal cortex and the gonads. Because they are lipid-based, they can easily diffuse across the fatty cell membrane to reach receptors inside the cell. You can often identify them by their chemical nomenclature; they frequently end in the suffixes '-one' (signifying a ketone group) or '-ol' (signifying an alcohol group), as seen in Cortisone, Testosterone, and Estradiol Science, Class X (NCERT 2025 ed.), Carbon and its Compounds, p.68. In the pharmaceutical industry, steroids like cortisone and progesterone are often synthesized from plant-based precursors such as Diosgenin Environment, Shankar IAS Academy (10th ed.), Plant Diversity of India, p.203.

In contrast, Peptide hormones consist of chains of amino acids. These range from short chains, like Oxytocin (a nonapeptide), to large proteins like Insulin. Unlike steroids, peptides are generally water-soluble (hydrophilic) and cannot pass through the lipid-rich cell membrane. Instead, they bind to receptors on the cell's surface to trigger a response. While many peptide hormones follow an '-in' naming convention (such as Insulin, Oxytocin, and Vasopressin), there are notable exceptions like Glucagon, which is a peptide hormone despite its different suffix.

Feature	Peptide Hormones	Steroid Hormones
Chemical Basis	Amino acid chains (Proteins)	Cholesterol (Lipids)
Solubility	Water-soluble (Hydrophilic)	Fat-soluble (Lipophilic)
Receptor Location	Cell surface (Membrane)	Inside the cell (Cytoplasm/Nucleus)
Common Suffixes	-in (usually)	-one, -ol
Examples	Insulin, Glucagon, Oxytocin	Cortisone, Cortisol, Estrogen

Sources: Science, Class X (NCERT 2025 ed.), Carbon and its Compounds, p.68; Environment, Shankar IAS Academy (10th ed.), Plant Diversity of India, p.203

8. Adrenal Gland: Cortex and Medulla (exam-level)

The adrenal glands (also known as suprarenal glands) are located like tiny 'caps' atop each kidney. Structurally and functionally, they are divided into two distinct parts: the outer adrenal cortex and the inner adrenal medulla. While the medulla is essentially an extension of the nervous system designed for rapid 'fight or flight' responses, the cortex is a glandular factory responsible for long-term metabolic and electrolyte balance. This dual nature ensures that the body can handle both immediate physical threats and long-term physiological stress Science, Class X (NCERT), p. 109. The adrenal cortex is responsible for synthesizing steroid hormones, which are chemically derived from cholesterol. These are categorized into three main groups: Glucocorticoids (like cortisol or cortisone), which regulate glucose metabolism and have anti-inflammatory properties; Mineralocorticoids (like aldosterone), which manage salt and water balance; and small amounts of sex steroids. Interestingly, the precursor for many of these steroids, such as cortisone and progesterone, can be synthesized commercially from Diosgenin, a compound found in wild yams Environment, Shankar IAS Academy, p. 203. In contrast, the adrenal medulla secretes adrenaline (epinephrine) and noradrenaline directly into the blood during emergencies. Unlike the slow-acting steroids of the cortex, adrenaline acts instantly to increase heart rate, breathing, and blood flow to muscles, ensuring the body is ready for vigorous activity. This chemical coordination is more widespread than electrical nerve impulses because the hormone reaches every cell in the body simultaneously Science, Class X (NCERT), p. 109-110.

Feature	Adrenal Cortex (Outer)	Adrenal Medulla (Inner)
Hormone Type	Steroids (Lipophilic)	Amino-acid derivatives (Catecholamines)
Key Hormones	Cortisol, Aldosterone, Cortisone	Adrenaline, Noradrenaline
Function	Metabolism, Salt balance, Long-term stress	Immediate 'Fight or Flight' response

Sources: Science, Class X (NCERT), Control and Coordination, p.109-110; Environment, Shankar IAS Academy, Plant Diversity of India, p.203

9. Solving the Original PYQ (exam-level)

Now that you have mastered the building blocks of the endocrine system, this question tests your ability to apply chemical classification to specific biological messengers. Recall from our conceptual lessons that hormones are structurally categorized into peptides (amino acid chains) and steroids (lipid-based molecules derived from cholesterol). This distinction is not just academic; it determines how a hormone travels through the blood and how it interacts with target cells. As noted in Science Class X (NCERT), understanding the functional and structural nature of these secretions is a fundamental requirement for the Civil Services Examination.

To arrive at the correct answer, we use the suffix strategy we practiced. Steroid hormones, which are synthesized in the adrenal cortex or gonads, typically carry the linguistic markers '-one' or '-ol'. Applying this logic, Cortisone—a glucocorticoid produced by the adrenal glands—is clearly identified as a steroid. In contrast, Insulin and Oxytocin follow the common naming convention for peptides/proteins (ending in '-in'). While Glucagon does not share that specific suffix, it is a well-known peptide hormone produced by the alpha cells of the pancreas. Therefore, through structural identification, (A) Cortisone is the only hormone in this list derived from cholesterol.

UPSC frequently uses "celebrity hormones" like Insulin and Glucagon as distractors because students often associate their high physiological importance with a steroid structure. However, the trap lies in forgetting that most metabolic regulators are protein-based. By remembering that steroids are limited primarily to the adrenal cortex (like Cortisone and Aldosterone) and reproductive hormones (like Testosterone and Estrogen), you can quickly eliminate the pancreatic and pituitary peptides that dominate the other options.