Endocrine Pharmacology Practice Questions

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

All of the above. ***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.

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 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 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 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

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

Accepted Answer

Carbimazole

Answer

Iodide

Answer

Propylthiouracil

Answer

Methimazole

Question 2

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 3

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

Accepted Answer

All of the above

Answer

Hypothyroidism

Answer

Pain at injection site

Answer

Glucose intolerance

Question 4

What is the mechanism of action of Pegvisomant?

Accepted Answer

GH receptor antagonist

Answer

Somatostatin antagonist

Answer

Somatotropin antagonist

Answer

GH receptor agonist

Question 5

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 6

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 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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