Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 741: A 47-year-old woman presents with complaints of nervousness and increased sensitivity to hot weather. She is diagnosed with hyperthyroidism and prescribed propylthiouracil. What is the principal mechanism by which this drug acts?

A. Reducing the proteolysis of thyroglobulin.
B. Inhibiting the binding of TSH to its receptor.
C. Inhibiting the enzyme thyroid peroxidase, which reduces the synthesis of thyroid hormones. (Correct Answer)
D. Altering the levels of reverse T3 (rT3) in the body.

Explanation: ***Inhibiting the enzyme thyroid peroxidase, which reduces the synthesis of thyroid hormones.*** - **Propylthiouracil (PTU)** is a **thionamide** drug that primarily acts by inhibiting the enzyme **thyroid peroxidase**. - Thyroid peroxidase is crucial for the **organification of iodide** and the **coupling of iodotyrosines** (MIT and DIT) to form T3 and T4, thus reducing the synthesis of thyroid hormones. *Inhibiting the binding of TSH to its receptor.* - This mechanism is characteristic of **TSH receptor antibodies**, which are a cause of hyperthyroidism (e.g., in Graves' disease), rather than the action of an antithyroid drug like PTU. - PTU works at the level of hormone synthesis within the thyroid gland, not at the receptor level for TSH. *Reducing the proteolysis of thyroglobulin.* - While thyroid hormones are stored as part of thyroglobulin, and their release involves proteolysis, this is not the **principal mechanism of action** for PTU. - The main effect of PTU is upstream, preventing the formation of the hormones themselves. *Altering the levels of reverse T3 (rT3) in the body.* - PTU does inhibit the **peripheral conversion of T4 to T3**, which can reduce overall T3 levels and increase rT3, but this is a **secondary mechanism**. - The primary and most significant action for reducing hyperthyroid symptoms is the direct inhibition of thyroid hormone synthesis within the gland.

Question 742: Which of the following statements about Selective Estrogen Receptor Modulators (SERMs) is correct?

A. Act as agonists on estrogen receptors.
B. Some SERMs can act as both agonists and antagonists on estrogen receptors. (Correct Answer)
C. Used to reduce the risk of hot flushes and thromboembolism.
D. Act as antagonists on estrogen receptors.

Explanation: ***Some SERMs can act as both agonists and antagonists on estrogen receptors.*** - **SERMs** (Selective Estrogen Receptor Modulators) exert tissue-specific effects, meaning they can act as an **estrogen receptor agonist** in some tissues while acting as an **antagonist** in others. - This **selective mechanism** allows them to confer beneficial estrogenic effects where desired (e.g., bone) and anti-estrogenic effects where unwanted (e.g., breast tissue). *Act as agonists on estrogen receptors.* - This statement is incomplete because while some SERMs can act as **agonists** in certain tissues (e.g., affecting bone density), they are not pure agonists across all tissues. - Their defining characteristic is their **selective action**, exhibiting mixed agonist and antagonist effects depending on the tissue. *Used to reduce the risk of hot flushes and thromboembolism.* - SERMs like **tamoxifen** and **raloxifene** can actually **increase the risk** of both hot flushes and thromboembolism. - **Hot flushes** occur due to their **anti-estrogenic effects** on the hypothalamus, which disrupts thermoregulation. - **Thromboembolism** risk is increased due to their **estrogenic (agonist) effects** on hepatic synthesis of coagulation factors. *Act as antagonists on estrogen receptors.* - This statement is also incomplete because, while some SERMs exhibit **antagonist activity** in certain tissues (e.g., the breast), they simultaneously act as **agonists** in other tissues (e.g., bone or endometrium). - A pure antagonist would block estrogen receptors in all tissues, which is not the defining feature of SERMs.

Question 743: Which drug is commonly used to treat hyperprolactinemia in women experiencing infertility?

A. Bromocriptine (Correct Answer)
B. Gonadotropin-Releasing Hormone (GnRH)
C. Testosterone (Androgen)
D. Corticosteroids

Explanation: ***Bromocriptine*** - **Bromocriptine** is a **dopamine agonist** that directly inhibits **prolactin secretion** from the pituitary gland. - By lowering prolactin levels, it helps restore **ovulatory function** and **fertility** in women with hyperprolactinemia. - It is the **first-line treatment** for hyperprolactinemia-induced infertility. *Gonadotropin-Releasing Hormone (GnRH)* - **GnRH** (or its agonists/antagonists) is primarily used to control **gonadotropin release** for conditions like **endometriosis** or **fibroids**, or in **assisted reproductive technologies**. - It does not directly treat hyperprolactinemia by inhibiting prolactin secretion. *Testosterone (Androgen)* - **Testosterone** is an **androgen** and is generally not used in women for infertility, especially not for hyperprolactinemia. - High testosterone levels in women can cause **hirsutism** and **anovulation**, which would worsen infertility. *Corticosteroids* - **Corticosteroids** are potent **anti-inflammatory** and **immunosuppressive** agents. - They are used to treat various autoimmune conditions or inflammation but have no direct role in treating hyperprolactinemia or female infertility in this context.

Question 744: A patient has Cushing syndrome due to an adrenal tumor. Which drug should be given?

A. Ketoconazole (Correct Answer)
B. Spironolactone
C. Hydrocortisone
D. Dexamethasone

Explanation: ***Ketoconazole*** - **Ketoconazole** is an antifungal agent that also inhibits several enzymes involved in **steroidogenesis**, including 17α-hydroxylase and 11β-hydroxylase. - This action helps to reduce the overproduction of **cortisol** in Cushing syndrome caused by an adrenal tumor. *Hydrocortisone* - **Hydrocortisone** is a glucocorticoid itself and would exacerbate the symptoms of **Cushing syndrome** by adding to the already elevated cortisol levels. - It is used for **cortisol replacement therapy** in conditions like Addison's disease, where cortisol levels are low. *Dexamethasone* - **Dexamethasone** is a potent synthetic glucocorticoid used to suppress **ACTH production** in cases of ACTH-dependent Cushing's syndrome (e.g., Cushing's disease) or to diagnose Cushing's syndrome. - In an adrenal tumor, which is **ACTH-independent**, dexamethasone would not reduce cortisol production but could instead worsen the hypercortisolism. *Spironolactone* - **Spironolactone** is an **aldosterone antagonist** and a weak antiandrogen, primarily used for conditions like hyperaldosteronism, heart failure, and hirsutism. - It has no direct effect on the overproduction of **cortisol** from an adrenal tumor in Cushing syndrome.

Question 745: Which of the following drugs can cause thyroid dysfunction?

A. Amiodarone (Correct Answer)
B. Ampicillin
C. Ibutilide
D. Acyclovir

Explanation: ***Amiodarone*** - **Amiodarone** is known to cause both **hypothyroidism** and **hyperthyroidism** due to its high iodine content and direct toxic effects on the thyroid gland. - Its effects can persist for months after discontinuation due to its **long half-life** and accumulation in tissues. *Ampicillin* - **Ampicillin** is an antibiotic that generally does not directly affect thyroid function. - Its primary mechanism of action involves inhibiting **bacterial cell wall synthesis**, with no known significant endocrine side effects. *Ibutilide* - **Ibutilide** is an antiarrhythmic drug used for recent-onset atrial fibrillation or flutter. - It works by blocking potassium channels and has no recognized association with thyroid dysfunction. *Acyclovir* - **Acyclovir** is an antiviral medication used to treat herpes virus infections. - Its mechanism of action involves inhibiting viral DNA replication and it is not known to impact thyroid hormone synthesis or metabolism.

Question 746: What is the drug of choice for pheochromocytoma?

A. Propranolol
B. Phenoxybenzamine (Correct Answer)
C. Prazosin
D. Nitroprusside

Explanation: ***Phenoxybenzamine*** - This is an **irreversible, non-selective alpha-adrenergic blocker**, which is the drug of choice for preparing patients for surgical removal of a pheochromocytoma. - It effectively controls **hypertension** by blocking the effects of catecholamines on blood vessels, preventing a hypertensive crisis during surgery. *Propranolol* - **Beta-blockers** like propranolol should **not be used as monotherapy** in pheochromocytoma because blocking beta-2 receptors without prior alpha blockade can lead to unopposed alpha-adrenergic vasoconstriction and precipitate a **hypertensive crisis**. - It can be added **after adequate alpha-blockade** to control tachycardia. *Prazosin* - Prazosin is a **reversible, selective alpha-1 adrenergic blocker**, which is not preferred over phenoxybenzamine due to its shorter duration of action and reversibility. - While it can lower blood pressure, its efficacy in preventing hypertensive crises during surgery for pheochromocytoma is **less robust** compared to phenoxybenzamine. *Nitroprusside* - Sodium nitroprusside is a **potent vasodilator** often used for **hypertensive emergencies**, but it is not the drug of choice for long-term management or preoperative preparation in pheochromocytoma. - Its use in pheochromocytoma is typically reserved for **acute hypertensive crises** when other agents are insufficient, rather than initial management.

Question 747: Which of the following statements about sitagliptin is false?

A. Used in type II diabetes mellitus
B. Cannot be used orally (Correct Answer)
C. Used in combination with other oral hypoglycemic agents
D. All of the above statements are true

Explanation: ***Cannot be used orally*** - This statement is **false** because **sitagliptin** is an **oral medication** approved for the treatment of type 2 diabetes mellitus. - As a **DPP-4 inhibitor**, it is designed to be taken by mouth to increase incretin hormone levels. *Used in type II diabetes mellitus* - This statement is **true** as **sitagliptin** is a commonly prescribed **oral antidiabetic drug** for the management of type 2 diabetes. - It works by inhibiting the enzyme **dipeptidyl peptidase-4 (DPP-4)**, which increases levels of **GLP-1** and **GIP** to enhance insulin secretion and reduce glucagon secretion. *Used in combination with other oral hypoglycemic agents* - This statement is **true** as **sitagliptin** is often used as **add-on therapy** with other oral hypoglycemic agents like **metformin** or a **sulfonylurea** when monotherapy is insufficient. - This combination approach helps achieve better glycemic control by targeting different mechanisms of action. *All of the above statements are true* - This statement is **false** because the first statement "Cannot be used orally" is incorrect. - Since sitagliptin is indeed an oral medication, not all the above statements are true, making this option incorrect.

Question 748: What conditions is Metformin primarily used to treat?

A. Only Type 2 Diabetes
B. Only Polycystic Ovary Syndrome (PCOS)
C. Both Type 2 Diabetes and Polycystic Ovary Syndrome (PCOS) (Correct Answer)
D. Pregnancy Induced Hypertension

Explanation: ***Both Type 2 Diabetes and Polycystic Ovary Syndrome (PCOS)*** - **Metformin** is a first-line treatment for **Type 2 Diabetes** due to its ability to decrease hepatic glucose production and improve insulin sensitivity [1], [2]. - It is also commonly used off-label for **PCOS** to improve insulin resistance, ovulation, and reduce androgen levels. *Only Type 2 Diabetes* - While Metformin is a cornerstone for **Type 2 Diabetes** treatment, stating "only" is incorrect as it has other significant therapeutic uses [2]. - Its benefits extend beyond diabetes management, particularly in conditions involving **insulin resistance**. *Only Polycystic Ovary Syndrome (PCOS)* - Metformin is used in **PCOS**, but it is not the sole condition it treats, and its primary indication remains **Type 2 Diabetes** [2]. - This option incorrectly limits its application to just one condition, overlooking its major role in diabetes. *Pregnancy Induced Hypertension* - **Metformin** is not indicated for the treatment of **pregnancy-induced hypertension** (gestational hypertension). - Treatment for pregnancy-induced hypertension typically involves medications like **labetalol**, **methyldopa**, or **nifedipine**, with delivery being the definitive management for severe cases.

Question 749: Which of the following is the longest acting glucocorticoid?

A. Prednisone
B. Prednisolone
C. Cortisone
D. Dexamethasone (Correct Answer)

Explanation: ***Correct: Dexamethasone*** - **Dexamethasone** is a long-acting glucocorticoid with a **biological half-life of 36–72 hours**, making it the longest acting among the options provided - Its prolonged action is due to its **high affinity for the glucocorticoid receptor** and relatively slow metabolism - Provides sustained anti-inflammatory and immunosuppressive effects *Incorrect: Prednisone* - **Prednisone** is an intermediate-acting glucocorticoid with a biological half-life of 12-36 hours - Requires metabolism in the liver to its active form, prednisolone - Duration of action is significantly shorter than dexamethasone *Incorrect: Prednisolone* - **Prednisolone** is the active form of prednisone, with a similar intermediate duration of action (12-36 hours) - Primarily used when liver conversion of prednisone is impaired - Does not possess the extended duration of action characteristic of dexamethasone *Incorrect: Cortisone* - **Cortisone** is a short-acting glucocorticoid with a biological half-life of 8-12 hours - It is a prodrug that needs to be converted to **hydrocortisone** (cortisol) in the liver to become active - Has the shortest duration among all options

Question 750: Which of the following antidiabetic drugs (other than insulin) is indicated as adjunct therapy for the management of both type I and type II diabetes mellitus?

A. Sulphonylureas
B. Metformin
C. Acarbose
D. Pramlintide (Correct Answer)

Explanation: Pramlintide - Pramlintide is an amylin analog indicated as an adjunct therapy to insulin for both type 1 and type 2 diabetes, helping to regulate post-prandial glucose. - It slows gastric emptying, suppresses postprandial glucagon secretion, and promotes satiety, leading to reduced insulin requirements and improved glycemic control. Sulphonylureas - Sulphonylureas primarily stimulate insulin secretion from pancreatic beta cells, making them effective only in Type 2 diabetes where some beta-cell function is preserved [2]. - They are not indicated for Type 1 diabetes because these patients have absolute insulin deficiency due to beta cell destruction. Metformin - Metformin is a biguanide that primarily reduces hepatic glucose production and improves insulin sensitivity in peripheral tissues. - It is a first-line treatment for Type 2 diabetes but is generally not used for Type 1 diabetes as it does not address the fundamental lack of insulin. Acarbose - Acarbose is an alpha-glucosidase inhibitor that works by delaying carbohydrate absorption from the gastrointestinal tract, thus reducing postprandial glucose spikes [1]. - While it can be used in Type 2 diabetes to manage postprandial hyperglycemia, it is not typically indicated as an adjunct for Type 1 diabetes alongside insulin [3].

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

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Pharmacological Management of Obesity

Practice Questions

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