Endocrine Pharmacology Practice Questions

Q: What is the mechanism of action of sulfonylureas?

K ATP channel blocker. ***K ATP channel blocker*** - Sulfonylureas bind to the **sulfonylurea receptor 1 (SUR1)** subunit of the **ATP-dependent potassium (KATP) channel** on pancreatic beta cells. - This binding leads to the closure of the KATP channels, causing **depolarization of the beta cell membrane** and subsequent **insulin release**. *Sodium channel blocker* - **Sodium channel blockers** are primarily used in conditions like **cardiac arrhythmias** and **epilepsy**, by stabilizing neuron membranes or altering cardiac action potentials. - They do not directly influence **insulin secretion** from pancreatic beta cells. *Calcium channel blocker* - **Calcium channel blockers** primarily inhibit the influx of calcium ions into cells, affecting **vascular smooth muscle** and **cardiac muscle**, which can influence blood pressure and heart rate. - While calcium influx is crucial for insulin release, sulfonylureas do not directly target these channels. *Chloride channel blocker* - **Chloride channel blockers** are not a primary mechanism of action for antidiabetic medications like sulfonylureas. - Their physiological roles are diverse, including involvement in **epithelial transport** and **cellular excitability**.

Q: What is the mechanism of action of Pegvisomant?

GH receptor antagonist. ***GH receptor antagonist*** - Pegvisomant is a **growth hormone (GH) receptor antagonist** that binds to GH receptors but does not activate them. - This action blocks the binding of endogenous GH to its receptors, thereby inhibiting the downstream production of **insulin-like growth factor 1 (IGF-1)** and reducing the symptoms of **acromegaly**. *Somatostatin antagonist* - **Somatostatin analogues** (e.g., octreotide, lanreotide) are used to treat acromegaly by inhibiting the release of growth hormone from the pituitary gland. - Pegvisomant does not act on somatostatin receptors; it functions at the level of the **GH receptor**. *Somatotropin antagonist* - **Somatotropin** is another name for **growth hormone (GH)**. - While Pegvisomant opposes the action of somatotropin, its mechanism is specifically at the receptor level, making "GH receptor antagonist" a more precise description. *GH receptor agonist* - A **GH receptor agonist** would stimulate the growth hormone receptor, leading to increased IGF-1 production and exacerbating conditions like acromegaly. - Pegvisomant has the opposite effect, blocking GH action rather than promoting it, making it an **antagonist**.

Q: Which of the following antithyroid medications had the maximum chances of causing agranulocytosis?

Carbimazole. ***Carbimazole*** - **Carbimazole** has the **highest reported incidence of agranulocytosis** among antithyroid drugs (approximately **0.3-0.5%**) - Although a prodrug of methimazole, **carbimazole itself** appears to confer additional risk beyond its active metabolite - **Agranulocytosis** typically occurs within the **first 2-3 months** of therapy and requires immediate discontinuation - Patients should be counseled to report **sore throat, fever, or mouth ulcers** immediately *Methimazole* - Has a **lower incidence** of agranulocytosis compared to carbimazole (approximately **0.1-0.3%**) - Once carbimazole is metabolized to methimazole, the risk profile changes - Still requires monitoring for this serious adverse effect *Propylthiouracil* - Has **comparable or slightly higher** agranulocytosis risk than methimazole but **lower than carbimazole** - More commonly associated with **hepatotoxicity** (including fulminant hepatic failure) - Preferred in **first trimester of pregnancy** and **thyroid storm** despite its risks *Iodide* - Works by **Wolff-Chaikoff effect** (inhibits thyroid hormone synthesis and release) - Does **not cause agranulocytosis** - Main adverse effects include **iodism**, hypothyroidism, and **Jod-Basedow phenomenon** (iodine-induced hyperthyroidism)

Q: Which of the following statements about tamoxifen is false?

It cannot be used for induction of ovulation.. ***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.

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

Maternal dexamethasone. ***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.

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

0.15 mg desogestrel. ***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.

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

Propylthiouracil. ***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.

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

Exenatide. ***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.

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

Ganirelix is a GnRH agonist.. ***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 1

What is the mechanism of action of sulfonylureas?

Accepted Answer

K ATP channel blocker

Answer

Sodium channel blocker

Answer

Calcium channel blocker

Answer

Chloride channel blocker

Question 2

What is the mechanism of action of Pegvisomant?

Accepted Answer

GH receptor antagonist

Answer

Somatostatin antagonist

Answer

Somatotropin antagonist

Answer

GH receptor agonist

Question 3

Which of the following antithyroid medications had the maximum chances of causing agranulocytosis?

Accepted Answer

Carbimazole

Answer

Iodide

Answer

Propylthiouracil

Answer

Methimazole

Question 4

Anti-inflammatory actions of corticosteroids are mediated by?

Accepted Answer

By inhibiting the production of inflammatory mediators derived from phospholipids

Answer

By inhibiting angiogenesis and reducing inflammation

Answer

By promoting vascular stability

Answer

By enhancing tissue repair mechanisms

Question 5

Which of the following statements about tamoxifen is false?

Accepted Answer

It cannot be used for induction of ovulation.

Answer

It increases the risk of venous thromboembolism.

Answer

It is a competitive inhibitor of estrogen at receptor site

Answer

It is a selective estrogen receptor modulator

Question 6

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

Accepted Answer

Maternal dexamethasone

Answer

Maternal hydrocortisone

Answer

Maternal methylprednisolone

Answer

Maternal cortisol

Question 7

Which of the following is not a component of Mala D?

Accepted Answer

0.15 mg desogestrel

Answer

0.03 mg Ethinyl estradiol

Answer

0.15 mg levonorgestrel

Answer

Iron tablets

Question 8

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

Accepted Answer

Propylthiouracil

Answer

Propranolol

Answer

Iodides

Answer

a and b both

Question 9

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

Accepted Answer

Exenatide

Answer

Repaglinide

Answer

Pioglitazone

Answer

Miglitol

Question 10

Which of the following statements about GnRH agonists is false?

Accepted Answer

Ganirelix is a GnRH agonist.

Answer

Long acting preparations can be used as nasal spray.

Answer

Used in cases of precocious puberty.

Answer

They have action similar to gonadotropin releasing hormone.

Endocrine Pharmacology — MCQs

Endocrine Pharmacology — MCQs

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