Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 721: What is the mechanism of action of Voglibose?

A. Beta-galactosidase inhibitor
B. Lactase inhibitor
C. Alpha-glucosidase inhibitor (Correct Answer)
D. Glucosidase inhibitor

Explanation: ***Alpha-glucosidase inhibitor*** - Voglibose acts by **inhibiting alpha-glucosidase enzymes** in the small intestine (maltase, sucrase, glucoamylase), which are responsible for breaking down complex carbohydrates into absorbable monosaccharides. - This delaying effect on carbohydrate digestion and absorption leads to a **reduction in postprandial glucose levels**, making it useful for managing type 2 diabetes. - The **alpha-specificity** is clinically important as it distinguishes this drug class from other enzyme inhibitors. *Beta-galactosidase inhibitor* - **Beta-galactosidase** is involved in the breakdown of lactose into glucose and galactose. - Inhibiting this enzyme would primarily affect **lactose digestion**, which is not the mechanism of Voglibose. - This is a completely different enzyme system unrelated to diabetes management. *Lactase inhibitor* - **Lactase** is a specific type of beta-galactosidase that breaks down lactose in the intestine. - Lactase inhibition would cause lactose intolerance symptoms, not affect glucose metabolism. - This does not describe the **carbohydrate-digesting enzyme inhibition** characteristic of Voglibose. *Glucosidase inhibitor* - While **technically accurate** (Voglibose does inhibit glucosidases), this term is **too general and non-specific** for pharmacological precision. - There are multiple types of glucosidases (alpha and beta) with different substrates and functions. - In pharmacology, specifying **alpha-glucosidase** is essential because it identifies the **exact enzyme target** and mechanism, which is critical for understanding drug action, side effects, and clinical use. - The best answer requires the most precise and clinically relevant terminology.

Question 722: Which of the following is/are side effect(s) of growth hormone administration?

A. All of the above (Correct Answer)
B. Hypothyroidism
C. Pain at injection site
D. Glucose intolerance

Explanation: ***All of the above*** - **Growth hormone (GH)** administration can lead to a variety of side effects, including **pain at the injection site**, **glucose intolerance**, and **hypothyroidism**. - These side effects are important considerations when managing patients receiving GH therapy. *Pain at injection site* - This is a common local side effect due to the injection method itself and the substance being administered. - It is typically mild and transient but can affect patient adherence to treatment. *Glucose intolerance* - Growth hormone has **anti-insulin effects**, which can lead to **insulin resistance** and increased blood glucose levels. - This can worsen pre-existing diabetes or induce **glucose intolerance** in susceptible individuals. *Hypothyroidism* - Growth hormone can influence thyroid function, sometimes reducing the conversion of **thyroxine (T4)** to **triiodothyronine (T3)**. - This may lead to **central hypothyroidism** or exacerbate subclinical hypothyroidism, requiring thyroid hormone supplementation.

Question 723: Which drug is preferred for the treatment of a 21-hydroxylase deficient female fetus to prevent genital virilization?

A. Maternal dexamethasone (Correct Answer)
B. Maternal hydrocortisone
C. Maternal methylprednisolone
D. Maternal cortisol

Explanation: ***Maternal dexamethasone*** - **Dexamethasone** is the preferred corticosteroid because it is not significantly metabolized by the placenta and can effectively reach the fetus to suppress adrenal androgen production. [2] - Its potent **glucocorticoid activity** helps to reduce the overproduction of androgens, preventing the virilization of external genitalia in affected female fetuses. [2] *Maternal cortisol* - **Cortisol** is rapidly metabolized by the placenta via **11β-hydroxysteroid dehydrogenase 2**, making it ineffective in reaching the fetal circulation in sufficient concentrations. - Therefore, it cannot adequately suppress the fetal adrenal gland's androgen production to prevent virilization. *Maternal hydrocortisone* - Similar to cortisol, **hydrocortisone** is also extensively metabolized by the placenta, reducing its bioavailability to the fetus. - It would not achieve the necessary fetal adrenal suppression to prevent **genital virilization**. [1] *Maternal methylprednisolone* - While **methylprednisolone** can cross the placenta, it is less potent than dexamethasone and may not provide sufficient suppression of fetal adrenal androgen synthesis. - **Dexamethasone** is generally considered more effective for this specific indication due to its superior placental transfer and potency.

Question 724: Which of the following statements about tamoxifen is false?

A. It increases the risk of venous thromboembolism.
B. It is a competitive inhibitor of estrogen at receptor site
C. It cannot be used for induction of ovulation. (Correct Answer)
D. It is a selective estrogen receptor modulator

Explanation: ***It cannot be used for induction of ovulation.*** - Tamoxifen, as a **selective estrogen receptor modulator (SERM)** with anti-estrogenic effects on the hypothalamus and pituitary, can in fact be used off-label for **ovulation induction** by increasing gonadotropin secretion. - Its anti-estrogenic action at the hypothalamus removes negative feedback, leading to increased **follicle-stimulating hormone (FSH)** release, which stimulates ovarian follicle development. *It increases the risk of venous thromboembolism.* - Tamoxifen exerts **estrogenic effects** on the coagulation system, which can lead to an increased risk of **venous thromboembolism (VTE)**, including deep vein thrombosis and pulmonary embolism. - This side effect is a significant concern, particularly in patients with other risk factors for clotting. *It is a competitive inhibitor of estrogen at receptor site* - Tamoxifen acts as a **selective estrogen receptor modulator (SERM)** by competitively binding to estrogen receptors in target tissues. - This binding prevents **endogenous estrogen** from activating the receptors, thereby exerting its anti-estrogenic effects, particularly in breast tissue. *It is a selective estrogen receptor modulator* - Tamoxifen is indeed classified as a **SERM**, meaning it has both estrogenic and anti-estrogenic effects depending on the target tissue. - It acts as an **estrogen antagonist** in breast tissue, making it effective in treating estrogen receptor-positive breast cancer, and an **estrogen agonist** in other tissues like bone and the endometrium.

Question 725: Which of the following is not a component of Mala D?

A. 0.03 mg Ethinyl estradiol
B. 0.15 mg levonorgestrel
C. Iron tablets
D. 0.15 mg desogestrel (Correct Answer)

Explanation: ***0.15 mg desogestrel*** - **Mala D** is a combined oral contraceptive pill that does not contain **desogestrel**. - **Desogestrel** is a progestin primarily found in some *third-generation combined oral contraceptives* or *progestin-only pills*, not Mala D. *0.03 mg Ethinyl estradiol* - **Mala D** contains **0.03 mg of Ethinyl estradiol**, which is the estrogen component of this combined oral contraceptive. - This dosage of estrogen helps to suppress ovulation and stabilize the endometrial lining. *0.15 mg levonorgestrel* - **Mala D** contains **0.15 mg of levonorgestrel**, which is the progestin component of this combined oral contraceptive. - **Levonorgestrel** works by thickening cervical mucus, inhibiting ovulation, and altering the endometrial lining. *Iron tablets* - **Mala D** packs typically include **iron tablets** (usually 75 mg of ferrous fumarate equivalent to 60 mg elemental iron) to be taken during the placebo week. - These iron tablets are included to help prevent or treat **iron-deficiency anemia**, which can occur with menstrual blood loss.

Question 726: HbA1C is decreased most by?

A. Thiazolidinediones
B. Sulfonylureas
C. Acarbose
D. Biguanides (Correct Answer)

Explanation: ***Biguanides***- **Metformin**, the primary biguanide, is considered a first-line agent for type 2 diabetes and can significantly lower **HbA1c** by 1.0-2.0% [1].- It primarily works by decreasing hepatic **glucose production** and increasing **insulin sensitivity** in peripheral tissues [1].*Sulfonylureas*- Sulfonylureas stimulate **insulin release** from pancreatic beta cells, thereby lowering blood glucose.- They typically decrease **HbA1c** by 1.0-2.0%, similar to biguanides, but are associated with a higher risk of **hypoglycemia** and weight gain.*Thiazolidinediones*- Thiazolidinediones (TZDs) improve **insulin sensitivity** in peripheral tissues and reduce hepatic glucose production [1].- They reduce **HbA1c** by approximately 0.5-1.5% but have a slower onset of action and are associated with side effects like **fluid retention** and weight gain [1].*Acarbose*- Acarbose is an **alpha-glucosidase inhibitor** that delays the absorption of carbohydrates in the small intestine, primarily reducing postprandial glucose excursions [2].- Its effect on **HbA1c** is more modest, typically lowering it by 0.5-0.8%, making it less potent for overall long-term glucose control compared to other agents.

Question 727: What is a special feature of glargine insulin?

A. It is suitable for once daily administration.
B. It is stable at physiological pH.
C. It is primarily used for basal insulin control.
D. It provides a long duration of action with a smooth, peakless effect. (Correct Answer)

Explanation: ***It provides a long duration of action with a smooth, peakless effect.*** - **Insulin glargine** is a **long-acting insulin analog** designed to provide a steady, basal insulin level over an extended period. - Its **peakless profile** minimizes the risk of hypoglycemia and offers continuous glycemic control for up to 24 hours. *It is suitable for once daily administration.* - While glargine is often administered once daily due to its **long duration of action**, this is a consequence of its pharmacological properties rather than its defining special feature. - Other long-acting insulins or even some intermediate-acting insulins can be given once daily, but glargine's strength lies in its **smooth, peakless profile**. *It is stable at physiological pH.* - **Insulin glargine** is formulated to be soluble in an acidic solution but precipitates into micro-precipitates at the **physiological pH** of subcutaneous tissue. - This precipitation allows for slow and sustained release, unlike the implication of direct stability at physiological pH. *It is primarily used for basal insulin control.* - **Basal insulin control** is indeed the primary purpose of glargine, providing a consistent background insulin level. - However, the 'special feature' is *how* it achieves this, which is through its **long duration** and **peakless profile**, making this option a consequence rather than the most distinct characteristic.

Question 728: Which of the following statements about GnRH agonists is false?

A. Long acting preparations can be used as nasal spray.
B. Used in cases of precocious puberty.
C. Ganirelix is a GnRH agonist. (Correct Answer)
D. They have action similar to gonadotropin releasing hormone.

Explanation: ***Ganirelix is a GnRH agonist.*** - **Ganirelix** is a **GnRH antagonist**, meaning it blocks the GnRH receptor and immediately suppresses gonadotropin release. - GnRH agonists initially stimulate the receptor, leading to a surge, before causing downregulation and desensitization. *Used in cases of precocious puberty.* - **GnRH agonists** are indeed used to treat **precocious puberty** by downregulating the GnRH receptors and suppressing endogenous gonadotropin-releasing hormone activity, which halts pubertal progression. - This therapy induces a temporary, reversible **hypogonadotropic hypogonadism**, effectively pausing inappropriate early puberty. *Long acting preparations can be used as nasal spray.* - Some **GnRH agonists**, like **buserelin**, are available as **nasal sprays** for long-term administration. - This route of administration allows for convenience and consistent delivery, particularly in conditions requiring chronic suppression. *They have action similar to gonadotropin releasing hormone.* - **GnRH agonists** are synthetic analogs of natural **gonadotropin-releasing hormone (GnRH)**, sharing a similar molecular structure. - They bind to and stimulate the GnRH receptors in the pituitary, initially causing increased **gonadotropin** release, followed by receptor desensitization and downregulation.

Question 729: Which of the following medications exhibits an incretin-like function?

A. Exenatide (Correct Answer)
B. Repaglinide
C. Pioglitazone
D. Miglitol

Explanation: ***Exenatide*** - **Exenatide** is a **glucagon-like peptide-1 (GLP-1) receptor agonist**, mimicking the action of naturally occurring incretin hormones. - It helps reduce blood glucose levels by **increasing glucose-dependent insulin secretion**, **reducing glucagon secretion**, and **slowing gastric emptying**. *Miglitol* - **Miglitol** belongs to the class of **alpha-glucosidase inhibitors**. - It works by delaying the digestion and absorption of carbohydrates in the small intestine, thereby reducing postprandial glucose levels. *Pioglitazone* - **Pioglitazone** is a **thiazolidinedione (TZD)** that acts as an agonist for **peroxisome proliferator-activated receptor-gamma (PPAR-γ)**. - It improves insulin sensitivity in peripheral tissues and the liver, leading to increased glucose uptake and utilization. *Repaglinide* - **Repaglinide** is a **meglitinide**, a class of **insulin secretagogues**. - It stimulates insulin release from pancreatic beta cells by binding to and closing ATP-sensitive potassium channels.

Question 730: Which of the following drugs can prevent the peripheral conversion of T4 to T3?

A. Propranolol
B. Iodides
C. a and b both
D. Propylthiouracil (Correct Answer)

Explanation: ***Propylthiouracil*** - Propylthiouracil (PTU) is a **thionamide drug** that inhibits thyroid peroxidase, thereby blocking the synthesis of thyroid hormones. - Additionally, PTU specifically inhibits the **5'-deiodinase enzyme**, which is responsible for the peripheral conversion of **thyroxine (T4)** to the more active **triiodothyronine (T3)**. - This is a **unique property** of PTU that distinguishes it from methimazole, making it preferred in thyrotoxic storm. *Propranolol* - Propranolol is a **beta-blocker** primarily used to alleviate the **symptomatic effects** of hyperthyroidism, such as palpitations, tremor, and anxiety. - Although high doses may have a minor effect on T4 to T3 conversion, this is **not clinically significant** and not the reason for its use in thyroid disorders. *Iodides* - High doses of iodides, such as **potassium iodide**, can acutely inhibit thyroid hormone release (the **Wolff-Chaikoff effect**) and decrease thyroid gland vascularity. - Iodides do **not prevent the peripheral conversion of T4 to T3**; their main action is on hormone synthesis and release from the thyroid gland itself. *a and b both* - This option is incorrect because neither propranolol nor iodides have a clinically significant effect on inhibiting peripheral 5'-deiodinase enzyme. - Only **propylthiouracil** has this specific and therapeutically relevant action.

Practice by Chapter

Hypothalamic and Pituitary Hormones

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Thyroid Drugs and Antithyroid Agents

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Insulin and Oral Hypoglycemic Agents

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Adrenocorticosteroids

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Sex Hormones: Estrogens and Progestins

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Androgens and Anabolic Steroids

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Hormonal Contraceptives

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Drugs Affecting Calcium Metabolism

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Drugs for Osteoporosis

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Pharmacological Management of Obesity

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