Endocrine system – nomenclature, stereochemistry, metabolism of steroids MCQs With Answer

Endocrine system – nomenclature, stereochemistry, metabolism of steroids MCQs With Answer

This concise guide for B. Pharm students covers the endocrine system with emphasis on steroid nomenclature, stereochemistry and metabolic pathways of steroid hormones. Key topics include the steroid nucleus (cyclopentanoperhydrophenanthrene), ring labeling and carbon numbering, base names (pregnane, androstane, estrane, cholestane), stereochemical descriptors (alpha/beta faces, R/S conventions), biosynthetic enzymes (CYP11A1, CYP17A1, CYP19A1, 5α-reductase), and Phase I/II metabolism (hydroxylation, reduction, glucuronidation, sulfation). Clinical and pharmacokinetic implications such as prodrug activation, oral bioavailability and drug interactions are highlighted. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which term correctly describes the common four-ring core structure of steroid hormones?

• Cyclopentanoperhydrophenanthrene
• Benzopyran nucleus
• Flavonoid backbone
• Porphyrin ring

Correct Answer: Cyclopentanoperhydrophenanthrene

Q2. Which base name corresponds to C21 saturated steroid skeleton used for progesterone derivatives?

• Androstane
• Estrane
• Pregnane
• Cholestane

Correct Answer: Pregnane

Q3. In steroid nomenclature, what does the prefix “17α-” indicate?

• A double bond at C17
• An alpha-oriented substituent at carbon 17
• Removal of C17 methyl group
• Epimerization at C3

Correct Answer: An alpha-oriented substituent at carbon 17

Q4. Which enzyme catalyzes the conversion of cholesterol to pregnenolone, initiating steroid biosynthesis?

• Aromatase (CYP19A1)
• 5α-Reductase
• Side-chain cleavage enzyme (CYP11A1, P450scc)
• 21-Hydroxylase (CYP21A2)

Correct Answer: Side-chain cleavage enzyme (CYP11A1, P450scc)

Q5. Aromatase (CYP19A1) converts which type of steroid into estrogens?

• Corticosteroids into mineralocorticoids
• Androgens into estrogens
• Progestogens into androgens
• Cholesterol into pregnenolone

Correct Answer: Androgens into estrogens

Q6. The designation “5α-reduced” refers to stereochemical change at which location?

• Removal of carbon 5 from the molecule
• Reduction at the double bond with hydrogen addition to the alpha face at C5
• Oxidation of the 5th carbon to a ketone
• Introduction of an alpha-methyl at C5

Correct Answer: Reduction at the double bond with hydrogen addition to the alpha face at C5

Q7. Which stereochemical notation indicates a substituent placed above the plane of the steroid nucleus?

• Alpha (α)
• Beta (β)
• Delta (δ)
• Gamma (γ)

Correct Answer: Beta (β)

Q8. Which enzyme deficiency leads to congenital adrenal hyperplasia characterized by impaired cortisol synthesis and accumulation of 17-hydroxyprogesterone?

• 11β-Hydroxylase deficiency (CYP11B1)
• 21-Hydroxylase deficiency (CYP21A2)
• Aromatase deficiency (CYP19A1)
• 17α-Hydroxylase deficiency (CYP17A1)

Correct Answer: 21-Hydroxylase deficiency (CYP21A2)

Q9. Which reaction is typically a Phase II metabolic pathway for steroid hormones?

• Hydroxylation by cytochrome P450
• Reduction of double bonds
• Glucuronidation by UDP-glucuronosyltransferases
• Side-chain cleavage by P450scc

Correct Answer: Glucuronidation by UDP-glucuronosyltransferases

Q10. The term “3β-hydroxy-Δ5” in steroid nomenclature indicates what functional features?

• Hydroxyl at C3 in beta orientation and a double bond between C5 and C6
• Ketone at C3 and double bond at C4–C5
• Hydroxyl at C3 alpha orientation and saturated C5
• Methyl substitution at C3 and triple bond at C5

Correct Answer: Hydroxyl at C3 in beta orientation and a double bond between C5 and C6

Q11. Which pathway enzyme has both 17α-hydroxylase and 17,20-lyase activities important for androgen synthesis?

• CYP11B1
• CYP17A1
• CYP21A2
• CYP11A1

Correct Answer: CYP17A1

Q12. Which structural change distinguishes estrogens from androgens in steroid chemistry?

• Loss of the D-ring
• Aromatization of the A-ring and loss of C19 methyl group
• Addition of a C21 side chain
• Saturation of all double bonds

Correct Answer: Aromatization of the A-ring and loss of C19 methyl group

Q13. Which metabolic modification increases water solubility of steroids for renal excretion?

• Cholesterol esterification
• Glucuronide or sulfate conjugation
• Lipophilic methylation
• Covalent binding to albumin

Correct Answer: Glucuronide or sulfate conjugation

Q14. In steroid structures, rings are labeled A–D. Which carbons belong to ring A?

• C1–C5 and C10
• C2–C6 and C7
• C1–C5 and C10
• C8–C12

Correct Answer: C1–C5 and C10

Q15. Ethinylestradiol has improved oral bioavailability primarily due to which modification?

• Conjugation with glucuronic acid
• 17α-ethinyl substitution that blocks first-pass oxidation at C17
• Removal of the A-ring
• Addition of a C21 side chain

Correct Answer: 17α-ethinyl substitution that blocks first-pass oxidation at C17

Q16. 5β-Reduction of steroids typically results in which geometric change at the A/B ring junction?

• Conversion to a trans (planar) junction
• Introduction of aromaticity in the A-ring
• Cis (bent) A/B ring junction with different biological activity
• Cleavage of the A-ring entirely

Correct Answer: Cis (bent) A/B ring junction with different biological activity

Q17. Which hepatic enzyme family is primarily responsible for Phase I hydroxylation of steroids?

• UDP-glucuronosyltransferases (UGTs)
• Sulfotransferases (SULTs)
• Cytochrome P450 monooxygenases (CYPs)
• Alcohol dehydrogenases

Correct Answer: Cytochrome P450 monooxygenases (CYPs)

Q18. The IUPAC-derived trivial name “androstane” indicates how many carbons in the backbone?

• C18
• C19
• C21
• C27

Correct Answer: C19

Q19. Which functional group modification is catalyzed by 11β-hydroxylase (CYP11B1)?

• Addition of a hydroxyl at C11, essential for cortisol biosynthesis
• Removal of the C19 methyl group to form estradiol
• Reduction of the C5–C6 double bond
• Conjugation with sulfate at C3

Correct Answer: Addition of a hydroxyl at C11, essential for cortisol biosynthesis

Q20. Which statement about steroid epimers is correct?

• Epimers differ in configuration at multiple stereocenters
• Epimers differ only at one stereocenter
• Epimers are stereoisomers that are non-superimposable mirror images
• Epimers always have identical biological activity

Correct Answer: Epimers differ only at one stereocenter

Q21. Which phase I transformation can inactivate an androgen and often precedes conjugation?

• Formation of an ether linkage
• Hydroxylation at specific ring positions
• Glucuronidation directly without modification
• Glycosylation at the side chain

Correct Answer: Hydroxylation at specific ring positions

Q22. Which steroid classification corresponds to C18 compounds like estradiol?

• Pregnane
• Cholestane
• Estrane
• Androstane

Correct Answer: Estrane

Q23. Which enzyme converts testosterone to the more potent dihydrotestosterone (DHT)?

• Aromatase (CYP19A1)
• 5α-Reductase
• 17β-Hydroxysteroid dehydrogenase type 3
• 21-Hydroxylase

Correct Answer: 5α-Reductase

Q24. Sulfation of steroid hormones by SULTs most commonly targets which functional group?

• Carbonyl groups at C20
• Hydroxyl groups such as phenolic or aliphatic OH
• Double bonds in the A-ring
• Methyl groups on the D-ring

Correct Answer: Hydroxyl groups such as phenolic or aliphatic OH

Q25. Which descriptor indicates a ketone at carbon 3 in a steroid name?

• 3α-OH
• 3β-OH
• 3-one
• Δ5

Correct Answer: 3-one

Q26. Where does the majority of steroid hormone metabolism occur in the body?

• Adipose tissue
• Bone marrow
• Liver
• Pancreas

Correct Answer: Liver

Q27. Which modification at C17 is commonly used in synthetic progestins to enhance oral activity?

• Introduction of a 17α-ethinyl or 17α-alkyl group
• Removal of the C17 carbon entirely
• Oxidation to a carboxylic acid at C17
• Attachment of a glucose moiety at C17

Correct Answer: Introduction of a 17α-ethinyl or 17α-alkyl group

Q28. Which statement about conjugated steroid metabolites in urine is TRUE?

• They are less polar than parent steroids
• They result from Phase I reactions only
• They are usually glucuronides or sulfates facilitating renal excretion
• They cannot be deconjugated by gut bacteria

Correct Answer: They are usually glucuronides or sulfates facilitating renal excretion

Q29. In naming steroids, what does “Δ4” signify?

• A double bond between carbon 4 and 5
• An oxygen at carbon 4
• A methyl group at carbon 4
• A hydroxyl at carbon 4

Correct Answer: A double bond between carbon 4 and 5

Q30. Which pharmacokinetic consequence results from extensive first-pass metabolism of oral steroids?

• Increased half-life due to active metabolites only
• Reduced oral bioavailability and potential need for higher doses or chemical modification
• Complete absence of Phase II reactions
• Enhanced potency without metabolic change

Correct Answer: Reduced oral bioavailability and potential need for higher doses or chemical modification

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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