Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 771: Which of the following statements about acarbose is incorrect?

A. It is an alpha-glucosidase inhibitor.
B. It does not delay the progression of diabetes. (Correct Answer)
C. Controls both pre and post prandial hyperglycemia.
D. It decreases fibrinogen levels.

Explanation: Phase 1: it does not delay the progression of diabetes - This statement is **incorrect** - clinical studies, particularly the **STOP-NIDDM trial**, have demonstrated that acarbose **can delay the progression from impaired glucose tolerance (IGT) to type 2 diabetes**. - Acarbose's mechanism of reducing postprandial glucose fluctuations helps in **beta-cell preservation** and improves insulin sensitivity, thereby modifying disease progression. - This is a well-established benefit of acarbose beyond just glycemic control. *It is an alpha-glucosidase inhibitor* - This is a **correct** statement - acarbose is indeed an **alpha-glucosidase inhibitor** that works in the small intestine [1]. - It inhibits enzymes that break down complex carbohydrates, thereby delaying glucose absorption and reducing postprandial glucose spikes [1], [3]. *It decreases fibrinogen levels* - While acarbose does not have a **direct, primary pharmacological effect** on fibrinogen levels, this statement is debatable. - Improved glycemic control with any antidiabetic agent can have indirect effects on various cardiovascular markers over time. - However, decreasing fibrinogen is not a recognized clinical indication or primary mechanism of acarbose [2]. *Controls both pre and post prandial hyperglycemia* - This is largely **correct** - acarbose is most effective at controlling **postprandial hyperglycemia** by delaying carbohydrate digestion and absorption [3]. - While its primary and strongest effect is on post-meal glucose spikes, improved overall glycemic control can contribute to modest improvements in fasting glucose levels as well.

Question 772: Which of the following antidiabetic drugs is NOT an insulin secretagogue?

A. Glinides
B. Exenatide
C. Pramlintide (Correct Answer)
D. Sulfonylureas

Explanation: ***Pramlintide*** - **Pramlintide** is an **amylin analog** which delays gastric emptying, suppresses glucagon secretion, and promotes satiety, thereby reducing postprandial glucose. It is **not an insulin secretagogue**. - Its mechanism of action is distinct from drugs that directly stimulate insulin release from pancreatic beta cells. - **This is the correct answer** as pramlintide has no role in enhancing insulin secretion. *Exenatide* - **Exenatide** is a **glucagon-like peptide-1 (GLP-1) receptor agonist** that enhances **glucose-dependent** insulin secretion. - Unlike traditional insulin secretagogues (sulfonylureas and glinides), GLP-1 agonists work through the **incretin effect** and only stimulate insulin release when glucose levels are elevated. - In strict pharmacological classification, GLP-1 agonists are **incretin mimetics**, not traditional insulin secretagogues, as they do not cause insulin release independent of glucose levels. - However, they do enhance insulin secretion in a physiological manner. *Glinides* - **Glinides**, such as repaglinide and nateglinide, are **insulin secretagogues** that stimulate rapid and short-lived insulin release from pancreatic beta cells. - They bind to the **sulfonylurea receptor** on beta cells, leading to membrane depolarization and insulin exocytosis. - Unlike GLP-1 agonists, glinides can cause insulin release **regardless of glucose levels**. *Sulfonylureas* - **Sulfonylureas**, such as glyburide and glipizide, are **insulin secretagogues** that stimulate insulin secretion by binding to the sulfonylurea receptor on pancreatic beta cells. - This binding leads to **closure of ATP-sensitive potassium channels**, membrane depolarization, and subsequent insulin release, regardless of blood glucose levels. - This glucose-independent action increases the risk of hypoglycemia compared to incretin-based therapies.

Question 773: What is the primary mechanism of action of propylthiouracil in the treatment of hyperthyroidism?

A. Inhibits iodine organification (Correct Answer)
B. Inhibits the synthesis of thyroglobulin
C. Inhibits the release of thyroid hormones T4 and T3
D. Inhibits the coupling of iodinated tyrosine residues

Explanation: ***Inhibits iodine organification*** - **Propylthiouracil (PTU)** primarily acts by blocking the enzyme **thyroid peroxidase (TPO)**, which catalyzes multiple steps in thyroid hormone synthesis. - TPO is responsible for the **oxidation of iodide and its incorporation into tyrosine residues** on thyroglobulin (organification). - By inhibiting TPO, PTU prevents the **iodination of tyrosine residues**, which is the first enzymatic step in thyroid hormone synthesis. - This is conventionally considered the primary mechanism as organification must occur before coupling can take place. *Inhibits the synthesis of thyroglobulin* - While thyroglobulin is essential for thyroid hormone production, PTU does not directly inhibit its synthesis. - PTU's action is on the enzymatic modification of already synthesized thyroglobulin, not on thyroglobulin production itself. *Inhibits the release of thyroid hormones T4 and T3* - This is primarily the mechanism of action of **iodides** (e.g., Lugol's solution), which block the release of preformed hormones from the thyroid gland via the Wolff-Chaikoff effect. - PTU's main effect is on synthesis, not release, although prolonged use can indirectly reduce stored hormone levels. *Inhibits the coupling of iodinated tyrosine residues* - PTU does inhibit the coupling of **monoiodotyrosine (MIT)** and **diiodotyrosine (DIT)** to form T3 and T4, as this reaction is also catalyzed by thyroid peroxidase. - However, since organification (iodination) must occur **before** coupling can take place, inhibition of organification is considered the **primary rate-limiting step**. - Both effects result from the same mechanism: **inhibition of thyroid peroxidase**.

Question 774: Non-hormonal drug to prevent postmenopausal osteoporosis is:

A. Alendronate (Correct Answer)
B. Estrogen
C. Raloxifene
D. Teriparatide

Explanation: ***Alendronate*** - **Alendronate** is a **bisphosphonate**, a class of non-hormonal drugs that inhibit **osteoclast** activity, thereby reducing bone resorption and increasing bone density. - It is a first-line treatment for **postmenopausal osteoporosis** and is effective in preventing fractures. *Estrogen* - **Estrogen** is a **hormonal therapy** used to prevent postmenopausal osteoporosis. - However, its use is associated with increased risks of **thromboembolism**, stroke, and certain cancers. *Raloxifene* - **Raloxifene** is a **selective estrogen receptor modulator (SERM)**. - While it has estrogen-like effects on bone, it is technically considered a **hormonal agent** because its mechanism of action involves interacting with estrogen receptors. *Teriparatide* - **Teriparatide** is a **parathyroid hormone (PTH) analog**, making it a **hormonal agent** that stimulates **osteoblast** activity to promote new bone formation. - It is an anabolic agent typically reserved for severe osteoporosis or those who have failed other therapies due to its injectable administration and higher cost.

Question 775: Which of the following describes the mechanism of action of acarbose?

A. It reduces post prandial hyperglycemia
B. It decreases the progression of impaired tolerance to overt diabetes mellitus
C. It can cause hypoglycemia
D. It acts by inhibiting the enzyme alpha-glucosidase (Correct Answer)

Explanation: ***It acts by inhibiting the enzyme alpha-glucosidase*** - **Acarbose** is an **alpha-glucosidase inhibitor**, which means it blocks the action of enzymes located in the brush border of the small intestine. - This inhibition delays the digestion of **complex carbohydrates** into absorbable monosaccharides, thereby slowing glucose absorption. *It reduces post prandial hyperglycemia* - While **acarbose** does reduce **postprandial hyperglycemia**, this is a **clinical effect** of the drug rather than its fundamental mechanism of action. - The reduction in blood glucose occurs *because* of its inhibitory action on alpha-glucosidase, not as the primary mechanism itself. *It decreases the progression of impaired tolerance to overt diabetes mellitus* - This is an observed **long-term benefit** of acarbose use, particularly in individuals with impaired glucose tolerance, but it is not its **direct pharmacological mechanism**. - This effect results from the sustained improvement in glucose control, reducing the stress on pancreatic beta cells. *It can cause hypoglycemia* - **Acarbose** alone generally **does not cause hypoglycemia** because its action is localized to the gut, delaying carbohydrate absorption rather than increasing insulin secretion or glucose uptake. - However, hypoglycemia can occur if acarbose is taken in combination with other anti-diabetic medications that *do* increase insulin levels (e.g., sulfonylureas or insulin).

Question 776: Prolonged corticosteroid therapy suppresses the hypothalamic-pituitary-adrenal (HPA) axis by primarily inhibiting the secretion of which hormone?

A. GH
B. ACTH (Correct Answer)
C. FSH
D. LH

Explanation: ***ACTH*** - **Corticosteroids** act via **negative feedback on the hypothalamic-pituitary-adrenal (HPA) axis**, suppressing the release of **corticotropin-releasing hormone (CRH)** from the hypothalamus and subsequently **ACTH** from the anterior pituitary. - This suppression of **ACTH** leads to **adrenal atrophy** and reduced endogenous **cortisol** production, which is why abrupt withdrawal after prolonged therapy can precipitate **adrenal crisis**. - **HPA axis suppression** is a clinically significant adverse effect requiring **gradual tapering** of corticosteroids and **stress-dose coverage** during illness or surgery. *GH* - **Growth hormone (GH)** is regulated by **GHRH** and **somatostatin**, not the HPA axis. - While chronic corticosteroid use can impair growth in children through multiple mechanisms (including direct effects on bone and cartilage), **GH suppression is not the primary mechanism** of HPA axis inhibition. *FSH* - **Follicle-stimulating hormone (FSH)** is a gonadotropin regulated by **GnRH** from the hypothalamus. - Corticosteroids do not primarily suppress **FSH** as part of their feedback mechanism on the HPA axis. *LH* - **Luteinizing hormone (LH)** is another gonadotropin regulated by the hypothalamic-pituitary-gonadal axis. - **LH suppression** is not part of the primary negative feedback mechanism by which corticosteroids inhibit the HPA axis.

Question 777: A rapid-acting insulin secretagogue effective in postprandial sugar control is:

A. Metformin
B. Repaglinide (Correct Answer)
C. Acarbose
D. Sulfonylurea

Explanation: ***Repaglinide*** - **Repaglinide** is a **meglitinide analog** that works by stimulating insulin release from pancreatic beta cells with a **rapid onset** and **short duration of action**. - Its rapid action makes it particularly effective in reducing **postprandial glucose excursions** when taken just before meals. - Provides **flexible dosing** - can be taken with meals and skipped if a meal is skipped. *Acarbose* - **Acarbose** is an **alpha-glucosidase inhibitor** that delays carbohydrate digestion and absorption in the small intestine. - While highly effective for postprandial glucose control through a different mechanism (delayed absorption vs. insulin secretion), it is **not an insulin secretagogue**. - Often causes gastrointestinal side effects like flatulence and abdominal discomfort. *Metformin* - **Metformin** is a **biguanide** that primarily reduces **hepatic glucose production** and improves insulin sensitivity. - Its main effect is on fasting glucose rather than specifically targeting rapid postprandial glucose spikes. - **Not an insulin secretagogue**. *Sulfonylurea* - **Sulfonylureas** stimulate insulin secretion but have a **longer duration of action** compared to meglitinides. - More associated with **hypoglycemia risk** if meals are irregular or skipped. - Less suitable for targeted postprandial control due to prolonged action.

Question 778: Which of the following is recombinant parathyroid hormone (rPTH) used in osteoporosis treatment?

A. Teriparatide (Correct Answer)
B. Calcipotriol
C. Denosumab
D. Calcitriol

Explanation: ***Teriparatide*** - **Teriparatide** is a **recombinant human parathyroid hormone (rPTH)**. It is an **anabolic agent** used in osteoporosis treatment. - Unlike antiresorptive agents, teriparatide **stimulates osteoblastic activity** and new bone formation, leading to increased bone mineral density and reduced fracture risk. *Calcipotriol* - **Calcipotriol** is a vitamin D analog primarily used topically for the treatment of **psoriasis**. - It works by regulating cell proliferation and differentiation in the skin, and is **not used for osteoporosis**. *Denosumab* - **Denosumab** is a **monoclonal antibody** that targets RANKL, inhibiting osteoclast formation and function, thus **reducing bone resorption**. - While it is a treatment for osteoporosis, it is an **antiresorptive agent**, not a recombinant parathyroid hormone. *Calcitriol* - **Calcitriol** is the **active form of vitamin D** and is used to treat conditions like hypocalcemia and metabolic bone disease associated with kidney failure. - It primarily helps with **calcium absorption** and bone mineralization, but it is not a recombinant parathyroid hormone and is not a primary anabolic treatment for osteoporosis.

Question 779: Which of the following is the drug of choice for Addison's disease?

A. Hydrocortisone (Correct Answer)
B. Betamethasone
C. Dexamethasone
D. Prednisolone

Explanation: ***Hydrocortisone*** - **Hydrocortisone** is the **glucocorticoid of choice** for Addison's disease because it most closely mimics the body's natural cortisol in terms of **potency and duration of action**. - It is preferred for **physiological replacement therapy** due to its short half-life (8-12 hours), allowing for dosing schedules that mimic the normal circadian rhythm of cortisol secretion. - While hydrocortisone has **some mineralocorticoid activity**, it is usually **combined with fludrocortisone** (a synthetic mineralocorticoid) to provide complete hormone replacement in Addison's disease. - The typical regimen is hydrocortisone **15-25 mg/day in divided doses** plus fludrocortisone **0.05-0.2 mg/day**. *Betamethasone* - **Betamethasone** is a **potent long-acting synthetic glucocorticoid** with **minimal mineralocorticoid activity**. - Its **long duration of action** and high potency make it unsuitable for daily physiological replacement therapy, as it increases the risk of **cushingoid side effects** and cannot mimic normal cortisol circadian rhythm. *Dexamethasone* - **Dexamethasone** is a **very potent long-acting glucocorticoid** with **no mineralocorticoid activity**. - Its **very long half-life (36-72 hours)** makes precise titration for physiological replacement extremely difficult and increases the risk of **overreplacement and cushingoid features**. - It is not suitable for routine replacement therapy in Addison's disease. *Prednisolone* - **Prednisolone** is an intermediate-acting glucocorticoid that can be used as an **alternative to hydrocortisone** for replacement therapy. - However, **hydrocortisone remains preferred** because its pharmacokinetic profile more closely matches physiological cortisol secretion. - Like hydrocortisone, prednisolone also requires **supplementation with fludrocortisone** for complete mineralocorticoid replacement.

Question 780: Which of the following drugs does not cause hypoglycemia?

A. Acarbose (Correct Answer)
B. Insulin
C. Glimepiride
D. Nateglinide

Explanation: ***Acarbose***- Acarbose is an **alpha-glucosidase inhibitor** that works by delaying carbohydrate digestion and glucose absorption in the gut.- Due to its mechanism of action, which does not stimulate insulin secretion or increase insulin sensitivity directly, it carries a **very low risk of hypoglycemia** when used as monotherapy [1].*Insulin*- **Insulin** is a direct hormone replacement therapy that lowers blood glucose by facilitating glucose uptake into cells.- Administered doses can sometimes exceed the body's needs, leading to **hypoglycemia**, especially with missed meals or increased physical activity [1].*Glimepiride*- Glimepiride is a **sulfonylurea** that stimulates insulin release from pancreatic beta cells, regardless of blood glucose levels.- This persistent stimulation can lead to **hypoglycemia**, which can be severe and prolonged.*Nateglinide*- Nateglinide is a **meglitinide**, a class of drugs that also stimulate insulin secretion from pancreatic beta cells [1, 2].- While its action is more rapid and short-lived compared to sulfonylureas, it still carries a risk of inducing **hypoglycemia**.

Practice by Chapter

Hypothalamic and Pituitary Hormones

Practice Questions

Thyroid Drugs and Antithyroid Agents

Practice Questions

Insulin and Oral Hypoglycemic Agents

Practice Questions

Adrenocorticosteroids

Practice Questions

Sex Hormones: Estrogens and Progestins

Practice Questions

Androgens and Anabolic Steroids

Practice Questions

Hormonal Contraceptives

Practice Questions

Drugs Affecting Calcium Metabolism

Practice Questions

Drugs for Osteoporosis

Practice Questions

Pharmacological Management of Obesity

Practice Questions

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