Endocrine System – Mechanism of Hormone Action (Elementary Idea): NEET MCQs with Answers

12 free questions on Endocrine System – Mechanism of Hormone Action (Elementary Idea) for NEET (UG), starting with previous-year NEET and AIPMT questions. Try each one, then tap Show answer for the answer and a short explanation.

Syllabus covered: Mechanism of Hormone Action (Elementary Idea)

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Question 1

Previous-year question
Regarding hormones, identify the correct statements and choose the most appropriate answer from the options given below. [NEET (Swaimadhopur) 2024]
A. Epinephrine is a peptide hormone.
B. Progesterone is a peptide hormone.
C. Hormones that interact with membrane-bound receptors normally do not enter the target cell, but generate second messengers.
D. Hormones that interact with intracellular receptors mostly regulate gene expression.
E. Insulin is an amino acid derivative hormone.
  1. C and E only
  2. C and D only
  3. B and C only
  4. A and B only
Show answer
Answer: (B) C and D only
Explanation: Hormones that bind membrane-bound receptors normally do not enter the target cell but generate second messengers (C correct), and hormones that bind intracellular receptors (steroids, iodothyronines) mostly regulate gene expression (D correct). Epinephrine is an amino acid derivative, progesterone is a steroid, and insulin is a peptide hormone, so A, B and E are incorrect.

Question 2

Previous-year question
Assertion: FSH, which interacts with membrane-bound receptors, does not enter the target cell. [Re-NEET 2022]
Reason: Binding of FSH to its receptors generates a second messenger (cyclic AMP) for its biochemical and physiological responses.
  1. Both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.
  2. Both Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.
  3. Assertion is true but the Reason is false.
  4. Assertion is false but the Reason is true.
Show answer
Answer: (B) Both Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.
Explanation: Both statements are true: FSH, a glycoprotein hormone, binds to membrane-bound receptors and does not enter the target cell, and its binding generates a second messenger (cAMP) that brings about biochemical and physiological responses. However, the generation of cAMP is a consequence of receptor binding and does not explain why the hormone stays outside the cell (that is due to its hydrophilic, large protein nature), so R is not the correct explanation of A.

Question 3

Previous-year question
Which one of the following endocrine glands stores its secretion in the extracellular space before discharging it into the blood? [AIPMT 1995]
  1. Testis
  2. Thyroid
  3. Pancreas
  4. Adrenal
Show answer
Answer: (B) Thyroid
Explanation: The thyroid gland secretes three hormones — tetraiodothyronine (T₄), triiodothyronine (T₃) and calcitonin. Thyroxine and triiodothyronine are iodinated forms of the amino acid tyrosine, and they are stored in the extracellular colloid that fills the follicles and released to the blood when needed.

Question 4

Previous-year question
Chemically, hormones are [AIPMT 2004]
  1. biogenic amines only
  2. proteins, steroids and biogenic amines
  3. proteins only
  4. steroids only
Show answer
Answer: (B) proteins, steroids and biogenic amines
Explanation: Chemically, hormones are of different natures — protein hormones (the hypothalamic hormones), steroids (the sex hormones) and biogenic amines (such as thyroxine).

Question 5

Previous-year question
Which one of the following is NOT a secondary messenger in hormone action? [AIPMT 2006]
  1. cAMP
  2. cGMP
  3. Calcium
  4. Sodium
Show answer
Answer: (D) Sodium
Explanation: Sodium is an essential nutrient which helps to maintain blood volume and keeps nerves functioning, but it is not a secondary messenger. Secondary messengers are low-weight diffusible molecules synthesised or released by specific enzymatic reactions, usually as a result of an external signal received by a transmembrane receptor; cAMP, cGMP and Ca²⁺ act as secondary messengers within the cytoplasm.

Question 6

Previous-year question
What is correct to say about hormone action in humans? [AIPMT 2012]
  1. Glucagon is secreted by β-cells of islets of Langerhans and stimulates glycogenolysis
  2. Secretion of thymosins is stimulated with ageing
  3. In females, FSH first binds with specific receptors on ovarian cell membrane
  4. FSH stimulates the secretion of oestrogen and progesterone
Show answer
Answer: (C) In females, FSH first binds with specific receptors on ovarian cell membrane
Explanation: FSH is a protein (glycoprotein) hormone, so it cannot enter the cell; it first binds to specific receptors on the membrane of ovarian follicle cells and acts through second messengers. Glucagon is secreted by alpha cells, thymosin secretion declines with ageing, and progesterone secretion is stimulated by LH.

Question 7

Previous-year question
Which one of the following pairs of hormones are the examples of those that can easily pass through the cell membrane of the target cell and bind to a receptor inside it (mostly in the nucleus)? [AIPMT 2012]
  1. Insulin, glucagon
  2. Thyroxine, insulin
  3. Somatostatin, oxytocin
  4. Cortisol, testosterone
Show answer
Answer: (D) Cortisol, testosterone
Explanation: Steroid hormones such as cortisol, testosterone, estradiol and progesterone regulate gene expression or chromosome function by interacting with the genome through a hormone-receptor complex. Being lipid-soluble, they easily pass through the cell membrane of the target cell and bind to a receptor inside it.
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Question 8

Previous-year question
Which of the following is an amino acid derived hormone? [NEET 2018]
  1. Epinephrine
  2. Ecdysone
  3. Estradiol
  4. Estriol
Show answer
Answer: (A) Epinephrine
Explanation: Epinephrine is derived from the amino acid tyrosine. It triggers the flight or fight response and is synthesised in the medulla of the adrenal glands.

Question 9

Previous-year question
How does a steroid hormone influence cellular activities? [NEET (National) 2019]
  1. Binding to DNA and forming a gene-hormone complex
  2. Activating cyclic AMP located on the cell membrane
  3. Using aquaporin channels as second messenger
  4. Changing the permeability of the cell membrane
Show answer
Answer: (A) Binding to DNA and forming a gene-hormone complex
Explanation: Steroid hormones are able to bind to DNA and form a gene-hormone complex. They easily cross the lipid bilayer of the cell and do not require second messengers, binding instead to intracellular receptors in the nucleus to form a hormone-receptor complex which then interacts with the genome. (Second messengers and changes in membrane permeability are required only for proteinaceous hormones, which cannot pass through the lipid bilayer on their own.)

Question 10

Previous-year question
Which of the following is NOT a steroid hormone? [NEET 2024]
  1. Cortisol
  2. Testosterone
  3. Progesterone
  4. Glucagon
Show answer
Answer: (D) Glucagon
Explanation: Glucagon is a peptide hormone produced by the α-cells of the pancreas; it raises the concentration of glucose and fatty acids in the blood stream. Cortisol, testosterone and progesterone are all examples of steroid hormones.

Question 11

Previous-year question
Which one of the following is NOT a second messenger in hormone action? [2006]
  1. Cyclic AMP
  2. Calcium
  3. Cyclic GMP
  4. Sodium
Show answer
Answer: (D) Sodium
Explanation: Second messengers relay the signal from a surface receptor to the interior of the cell, and cyclic AMP, cyclic GMP, calcium ions, inositol triphosphate and diacylglycerol all serve in this way. Sodium is important in generating membrane potentials but is not used as a second messenger.

Question 12

Previous-year question
According to the accepted concept of hormone action, if receptor molecules are removed from target organs, the target organ will [1996]
  1. continue to respond to the hormone but in the opposite way
  2. not respond to the hormone
  3. continue to respond but require a higher concentration
  4. continue to respond without any difference
Show answer
Answer: (B) not respond to the hormone
Explanation: A hormone circulates to every tissue but acts only where a specific receptor is present to recognise it, and it is the binding of hormone to receptor that initiates the response. Without the receptor the cell cannot detect the hormone at all, so no response occurs at any concentration.

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