Try this first
Answer: B. Hormones are intercellular messengers produced by endocrine glands and poured directly into the blood stream, which transports them to the site of action (NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, page 430).
A is wrong: A is wrong because hormones are poured into the blood stream and travel to their site of action; they do not stay in the gland.
C is wrong: C is wrong because hormones are produced in the body by endocrine glands rather than being supplied only through the diet.
D is wrong: D is wrong because NCERT describes hormones as messengers made by endocrine glands, not as breakdown fragments.
Insulin, thyroxine, testosterone and epinephrine are all hormones, yet they are chemically four different kinds of molecule. What do the first three have in common, and why does a pinch of sodium iodide in table salt matter?
The 2026 NEET syllabus lists "Hormones (General introduction)" under Biomolecules. The rationalised Class 12 Biomolecules chapter no longer contains hormone text, so this lesson uses the pre-2023 edition of the NCERT chapter, section 14.6.
What a hormone is. Hormones are molecules that act as intercellular messengers. They are produced by endocrine glands and poured directly into the blood stream, which carries them to the site of action (NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, page 430).
Chemical nature. Some are steroids (estrogens, androgens), some are polypeptides (insulin, endorphins) and some are amino acid derivatives (epinephrine, norepinephrine) (page 430).
Functions you can be asked.
NEET watch-out: sort hormones by chemical class first. Insulin is a polypeptide, epinephrine an amino acid derivative, thyroxine an iodinated tyrosine derivative, and the adrenal cortex and gonad hormones are steroids.
Given
A person living where the diet is low in iodine is lethargic and gaining weight, and the thyroid gland is enlarged.
Required
Name the condition and the hormone involved, say what chemical kind of hormone it is, and state the control measure.
Concept
Thyroxine from the thyroid gland is an iodinated derivative of the amino acid tyrosine (NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, page 430). Abnormally low thyroxine gives hypothyroidism, characterised by lethargy and obesity, and low iodine in the diet can enlarge the thyroid gland (page 431).
Formula
No numerical formula applies. The chain is: low dietary iodine, then low thyroxine, then hypothyroidism.
Substitution
Map the case onto the chain. Low iodine in the diet matches the first link. Lethargy and weight gain match hypothyroidism. The enlarged thyroid matches the NCERT statement on low iodine.
Calculation
Check against the alternatives. Hyperthyroidism needs an increased thyroxine level, but the symptoms are those of a low level. Addison's disease concerns the adrenal cortex, not the thyroid. So the thyroid chain is the one that fits. No numerical constants are involved here, exact or measured.
Final answer
The condition is hypothyroidism; the hormone is thyroxine, an iodinated derivative of the amino acid tyrosine. It is controlled by adding sodium iodide to table salt ("iodised" salt).
Common trap
Calling it hyperthyroidism because the thyroid is enlarged. The enlargement here comes from low iodine; hyperthyroidism means a raised thyroxine level, and the symptoms described are those of a low level.
Similar NEET-style question
A steroid hormone made by the testes is responsible for a deep voice, facial hair and general physical constitution. Name it. (Answer: testosterone. Steroid hormones come from the adrenal cortex and the gonads, and testosterone is the major sex hormone produced in males, responsible for the secondary male characteristics listed.)
Select an option to see the explanation. Wrong answers show why your choice was tempting — and name the exact trap it exploits.
In NCERT's description, hormones are
Answer: B. Hormones are intercellular messengers produced by endocrine glands and poured directly into the blood stream, which transports them to the site of action (NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, page 430).
Why A is wrong: A is wrong because hormones are poured into the blood stream and travel to their site of action; they do not stay in the gland.
Why C is wrong: C is wrong because hormones are produced in the body by endocrine glands rather than being supplied only through the diet.
Why D is wrong: D is wrong because NCERT describes hormones as messengers made by endocrine glands, not as breakdown fragments.
Which of these hormones is a polypeptide?
Answer: D. NCERT lists insulin and endorphins as polypeptide hormones (NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, page 430).
Why A is wrong: A is wrong because epinephrine is an amino acid derivative, as is norepinephrine.
Why B is wrong: B is wrong because testosterone is a steroid hormone released by the gonads.
Why C is wrong: C is wrong because thyroxine is an iodinated derivative of the amino acid tyrosine.
Hormones released by the adrenal cortex and by the gonads are chemically
Answer: A. Steroid hormones are produced by the adrenal cortex and the gonads (testes in males and ovaries in females) (NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, page 431).
Why B is wrong: B is wrong because the polypeptide hormones NCERT names are insulin and endorphins.
Why C is wrong: C is wrong because the amino acid derivatives named are epinephrine, norepinephrine and, through tyrosine, thyroxine.
Why D is wrong: D is wrong because NCERT does not classify any hormone as a carbohydrate.
Thyroxine is
Answer: C. Thyroxine produced in the thyroid gland is an iodinated derivative of the amino acid tyrosine (NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, page 430).
Why A is wrong: A is wrong because the adrenal cortex releases glucocorticoids and mineralocorticoids, and thyroxine comes from the thyroid gland.
Why B is wrong: B is wrong because the polypeptides NCERT lists are insulin and endorphins, not thyroxine.
Why D is wrong: D is wrong because the gonads release testosterone, estradiol and progesterone, not thyroxine.
Why is sodium iodide added to commercial table salt?
Answer: D. Low iodine in the diet may lead to hypothyroidism and enlargement of the thyroid gland, and this is largely controlled by adding sodium iodide to table salt (NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, page 431).
Why A is wrong: A is wrong because raising glucose is the tendency of glucagon, not a purpose of iodised salt.
Why B is wrong: B is wrong because iodide is an ingredient for thyroxine, not a source of steroid hormones.
Why C is wrong: C is wrong because Addison's disease follows poor functioning of the adrenal cortex, not iodine shortage.
After a meal, blood glucose rises rapidly. Which hormone is released in response?
Answer: A. Insulin is released in response to a rapid rise in blood glucose and keeps the level within narrow limits (NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, page 430).
Why B is wrong: B is wrong because glucagon tends to increase the glucose level; it works together with insulin but is not the response to a rise.
Why C is wrong: C is wrong because epinephrine mediates responses to external stimuli.
Why D is wrong: D is wrong because testosterone is a sex hormone concerned with male secondary characteristics.
A patient's adrenal cortex is not functioning properly, and the patient shows hypoglycemia, weakness and increased susceptibility to stress. What is the condition and how is it treated?
Answer: C. Addison's disease is characterised by hypoglycemia, weakness and increased susceptibility to stress; it is fatal unless treated with glucocorticoids and mineralocorticoids (NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, page 431).
Why A is wrong: A is wrong because hyperthyroidism is caused by an increased level of thyroxine, and iodised salt addresses iodine shortage.
Why B is wrong: B is wrong because hypothyroidism is a thyroxine shortage with lethargy and obesity, and the adrenal cortex is not involved.
Why D is wrong: D is wrong because testosterone is a sex hormone and does not treat adrenal failure.
Which pairing of hormone and function is correct?
Answer: B. Progesterone is responsible for preparing the uterus for implantation of the fertilised egg (NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, page 431).
Why A is wrong: A is wrong because it swaps the pair: glucocorticoids control carbohydrate metabolism, and mineralocorticoids control water and salt excretion.
Why C is wrong: C is wrong because it also swaps the pair: mineralocorticoids, not glucocorticoids, control excretion of water and salt.
Why D is wrong: D is wrong because estradiol is the main female sex hormone; testosterone is the major male one.
Get a structured 30-day study plan and a complete formula booklet — delivered to your inbox instantly.
In the NEET syllabus; removed from current NCERT.
Hormones are molecules that act as intercellular messengers. These are produced by endocrine glands in the body and are poured directly in the blood stream which transports them to the site of action.
-- NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, p. 430In the NEET syllabus; removed from current NCERT.
In terms of chemical nature, some of these are steroids, e.g., estrogens and androgens; some are poly peptides for example insulin and endorphins and some others are amino acid derivatives such as epinephrine and norepinephrine.
-- NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, p. 430In the NEET syllabus; removed from current NCERT.
Insulin is released in response to the rapid rise in blood glucose level. On the other hand hormone glucagon tends to increase the glucose level in the blood. The two hormones together regulate the glucose level in the blood.
-- NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, p. 430In the NEET syllabus; removed from current NCERT.
Epinephrine and norepinephrine mediate responses to external stimuli. Growth hormones and sex hormones play role in growth and development.
-- NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, p. 430In the NEET syllabus; removed from current NCERT.
Thyroxine produced in the thyroid gland is an iodinated derivative of amino acid tyrosine.
-- NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, p. 430In the NEET syllabus; removed from current NCERT.
hypothyroidism which is characterised by lethargyness and obesity. Increased level of thyroxine causes hyperthyroidism. Low level of iodine in the diet may lead to hypothyroidism and enlargement of the thyroid gland. This condition is largely being controlled by adding sodium iodide to commercial table salt (“Iodised” salt).
-- NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, p. 431In the NEET syllabus; removed from current NCERT.
Steroid hormones are produced by adrenal cortex and gonads (testes in males and ovaries in females).
-- NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, p. 431In the NEET syllabus; removed from current NCERT.
Hormones released by the adrenal cortex play very important role in the functions of the body. For example, glucocorticoids control the carbohydrate metabolism, modulate inflammatory reactions, and are involved in reactions to stress. The mineralocorticoids control the level of excretion of water and salt by the kidney. If adrenal cortex does not function properly then one of the results may be Addison’s disease characterised by hypoglycemia, weakness and increased susceptibility to stress. The disease is fatal unless it is treated by glucocorticoids and mineralocorticoids.
-- NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, p. 431In the NEET syllabus; removed from current NCERT.
Hormones released by gonads are responsible for development of secondary sex characters. Testosterone is the major sex hormone produced in males. It is responsible for development of secondary male characteristics (deep voice, facial hair, general physical constitution) and estradiol is the main female sex hormone. It is responsible for development of secondary female characteristics and participates in the control of menstrual cycle. Progesterone is responsible for preparing the uterus for implantation of fertilised egg.
-- NCERT Class 12 Chemistry (pre-2023 edition), Chapter 14, p. 431No question in our NEET 2020–2025 set targets this topic directly.
More in Biomolecules: 4 exam traps and mistakes · 3 formulas · 1 question pattern from its other lessons.
Page numbers are the ones printed in the current NCERT textbook (2023 rationalised edition), unless marked pre-2023. The books are free at ncert.nic.in.
Every past-paper question from this chapter:
Practice the whole chapter →