Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 781: The progestogenic emergency contraceptive pills act by:

A. Prevention of implantation of a fertilized egg
B. Prevention of ovulation if not already occurred (Correct Answer)
C. Induction of endometrial shedding
D. Modification of cervical mucus to reduce sperm penetration

Explanation: ***Prevention of ovulation if not already occurred*** - Progestogenic emergency contraceptive pills primarily work by **delaying or inhibiting ovulation**, thereby preventing the release of an egg for fertilization. - This mechanism is effective when taken before the surge of **luteinizing hormone (LH)**, which triggers ovulation. - According to **WHO and FIGO guidelines**, this is the primary and most well-established mechanism of action. *Prevention of implantation of a fertilized egg* - Current scientific evidence from **WHO (2015)** and **ICMR guidelines** clearly establishes that progestogenic emergency contraceptives (like levonorgestrel) do **NOT prevent implantation** of a fertilized egg. - Studies show these pills are ineffective once fertilization has occurred, confirming they work solely through **pre-fertilization mechanisms** (primarily ovulation inhibition). - This distinction is important for understanding that progestogenic ECs are **contraceptives, not abortifacients**. *Induction of endometrial shedding* - This is a mechanism associated with **mifepristone (RU-486)**, an abortifacient, which causes shedding of the uterine lining, not with progestogenic emergency contraceptives. - Progestogenic emergency contraceptives do not induce endometrial shedding as their mode of action. *Modification of cervical mucus to reduce sperm penetration* - This is a known effect of **regular progestin-only contraceptives** (e.g., mini-pills taken daily) but is not the primary mechanism by which progestogenic emergency contraceptive pills prevent pregnancy. - While some cervical mucus thickening may occur, the main efficacy is due to **ovulation inhibition**, as the single high dose used in emergency contraception works differently than continuous low-dose regimens.

Question 782: Which of the following is a nasally acting GnRH analogue?

A. Triptorelin
B. Nafarelin (Correct Answer)
C. Leuprolide
D. Goserelin

Explanation: ***Nafarelin (Correct Answer)*** - **Nafarelin** is available as a **nasal spray** (Synarel®), making it a nasally acting GnRH analogue - Administered intranasally for conditions like **endometriosis** and **central precocious puberty** - Its formulation is designed for efficient absorption through the **nasal mucosa** *Goserelin (Incorrect)* - Administered as a **subcutaneous implant** (Zoladex®) for sustained release, not nasally - Used in hormone therapy for **prostate cancer**, **breast cancer**, and **endometriosis** - Not available in nasal formulation *Triptorelin (Incorrect)* - Provided as an **intramuscular or subcutaneous injection** in sustained-release depot formulation - Used for hormone-sensitive cancers and **assisted reproductive technology** - Not formulated for **nasal administration** *Leuprolide (Incorrect)* - Administered via **subcutaneous or intramuscular injection** (Lupron®), including depot formulations - Used for prostate cancer, endometriosis, and uterine fibroids - **Not available in nasal form** for clinical use

Question 783: Which of the following drugs does not act on the thyroid?

A. Propranolol (Correct Answer)
B. Propylthiouracil
C. Sodium iodide
D. Thiocyanate

Explanation: ***Propranolol*** - **Propranolol** is a **beta-blocker** primarily used to relieve symptoms of hyperthyroidism such as palpitations, tremor, and anxiety by blocking beta-adrenergic receptors. - It does not directly affect thyroid hormone production or release, making it a symptomatic treatment rather than an antithyroid drug. *Propylthiouracil* - **Propylthiouracil (PTU)** is a **thionamide** drug that directly inhibits the synthesis of thyroid hormones by interfering with the **thyroid peroxidase enzyme**. - It also blocks the peripheral conversion of **thyroxine (T4)** to the more active **triiodothyronine (T3)**. *Sodium iodide* - High doses of **iodine**, such as **sodium iodide**, acutely inhibit thyroid hormone synthesis and release, a phenomenon known as the **Wolff-Chaikoff effect**. - It is often used in preparation for surgery in hyperthyroid patients or during thyroid storm. *Thiocyanate* - **Thiocyanate** is an **anion** that competitively inhibits the **iodide transporter (NIS)** in the thyroid gland. - By blocking the uptake of iodide into thyroid cells, it reduces the availability of iodine for thyroid hormone synthesis.

Question 784: The adverse effect of combined oral contraceptives among the following is:

A. Pelvic inflammatory disease (PID)
B. Weight changes
C. Acne based on formulation
D. Liver disorders (Correct Answer)

Explanation: ***Liver disorders*** - Combined oral contraceptives (COCs) can cause adverse effects on the liver, including **cholestasis**, adenomas, and, rarely, **hepatocellular carcinoma**. - This is primarily due to the **estrogen component** which can affect liver metabolism and function. *Pelvic inflammatory disease (PID)* - COCs have been shown to **reduce the risk of PID** by thickening cervical mucus, which acts as a barrier to ascending infections. - PID is typically caused by sexually transmitted infections, not directly by COC use. *Weight changes* - While some women report weight changes, large-scale studies have not found a significant or consistent **causal link between COCs and weight gain**. - Any perceived weight changes are often transient or related to other factors, such as fluid retention. *Acne based on formulation* - Many COCs are actually prescribed to **treat acne** due to their anti-androgenic effects, particularly formulations with newer progestins. - While some specific older formulations might worsen acne in susceptible individuals, it is not a general adverse effect of COCs.

Question 785: Emmenagogues are the drugs that

A. Induce menstruation (Correct Answer)
B. Induce uterine contractions
C. Increase perspiration
D. Induce nausea

Explanation: ***Induce menstruation*** - **Emmenagogues** are substances that stimulate or increase menstrual flow. This definition directly aligns with their pharmacological action. - They are often used in traditional medicine for **amenorrhea** (absence of menstruation) or oligomenorrhea (infrequent menstruation). *Induce uterine contractions* - Drugs that induce uterine contractions are called **oxytocics**, such as oxytocin and prostaglandins. - While some emmenagogues might have mild uterine stimulant effects, their primary definition and purpose are to induce menstruation, not just any uterine contraction. *Increase perspiration* - Drugs that increase perspiration (sweating) are known as **diaphoretics** or sudorifics. - This effect is unrelated to the definition or action of emmenagogues. *Induce nausea* - Drugs that induce nausea are called **emetogenic** agents or emetics, and are used to induce vomiting. - This effect has no relation to the function of emmenagogues, which target the menstrual cycle.

Question 786: Which of the following steroids possesses maximum glucocorticoid activity?

A. Prednisolone
B. Aldosterone
C. Dexamethasone (Correct Answer)
D. Cortisol

Explanation: ***Dexamethasone*** - **Dexamethasone** is a synthetic glucocorticoid with high potency, making it one of the steroids with the **maximum glucocorticoid activity** [1], [2]. - It exhibits a much longer duration of action and significantly greater anti-inflammatory effects compared to natural glucocorticoids like cortisol [2]. *Prednisolone* - **Prednisolone** is a synthetic glucocorticoid that has approximately four times the anti-inflammatory potency of cortisol [1]. - While potent, it does not reach the glucocorticoid activity levels of dexamethasone. *Cortisol* - **Cortisol** is the body's primary natural glucocorticoid, involved in stress response and metabolism [2]. - Its glucocorticoid activity serves as a baseline for comparing the potencies of other synthetic corticosteroids [2]. *Aldosterone* - **Aldosterone** is primarily a mineralocorticoid, not a glucocorticoid, with its main role being the regulation of electrolyte and water balance [2]. - It possesses minimal to no glucocorticoid activity.

Question 787: Which of the following statements about bromocriptine therapy is incorrect?

A. If pregnancy occurs there is increased incidence of multiple pregnancy
B. It is used to inhibit inappropriate lactation with secondary amenorrhea
C. It is specific in suppressing only the prolactin secretion (Correct Answer)
D. Its teratogenic effect on the fetus is inconclusive

Explanation: ***It is specific in suppressing only the prolactin secretion*** - **Bromocriptine**, a dopamine agonist, is not specific to prolactin and can reduce the secretion of **growth hormone** in patients with **acromegaly**, as well as other anterior pituitary hormones. - Its action is to stimulate **dopamine receptors**, which then inhibits prolactin release. However, it can also have effects on other hormonal pathways due to the widespread nature of dopamine receptors. *It is used to inhibit inappropriate lactation with secondary amenorrhea* - **Bromocriptine** is a primary treatment for **hyperprolactinemia**, which often manifests as **galactorrhea (inappropriate lactation)** and **amenorrhea**. - By reducing **prolactin levels**, it can restore normal ovulatory cycles and cease lactation. *If pregnancy occurs there is increased incidence of multiple pregnancy* - While bromocriptine can induce ovulation in previously anovulatory women, leading to pregnancy, it is not associated with an **increased incidence of multiple pregnancies**. - The risk of **multiple births** is primarily linked to fertility treatments that stimulate multiple ovulations simultaneously, which is not the direct mechanism of bromocriptine. *Its teratogenic effect on the fetus is inconclusive* - Studies on bromocriptine use during early pregnancy have not shown a significantly increased risk of **teratogenic effects** or adverse pregnancy outcomes. - However, due to limited extensive data, especially at higher doses or prolonged use early in pregnancy, its use is typically **discontinued once pregnancy is confirmed**.

Question 788: A patient on tamoxifen therapy is most likely to develop which of the following?

A. Increased risk of breast cancer
B. Increased LDL cholesterol levels
C. Endometrial hyperplasia (Correct Answer)
D. Increased risk of myocardial infarction

Explanation: ***Endometrial hyperplasia*** - Tamoxifen acts as an **estrogen receptor agonist** in the uterus, stimulating endometrial proliferation and increasing the risk of hyperplasia, polyps, and endometrial cancer. - This effect is particularly seen in **postmenopausal women** and is a major concern with long-term use. *Increased risk of breast cancer* - Tamoxifen is primarily used to **reduce the risk of breast cancer recurrence** and as a chemopreventive agent in high-risk individuals. - It acts as an **estrogen receptor antagonist** in breast tissue, blocking estrogen's proliferative effects. *Increased LDL cholesterol levels* - Tamoxifen typically has a favorable effect on lipids, often causing a **decrease in total and LDL cholesterol** levels. - This effect is due to its estrogenic activity in the liver. *Increased risk of myocardial infarction* - While tamoxifen can increase the risk of **thromboembolic events** (e.g., DVT, pulmonary embolism), it generally does not increase, and may even decrease, the risk of myocardial infarction due to its beneficial effects on lipid profiles. - Its overall cardiovascular risk profile is complex, but MI is not a commonly cited side effect.

Question 789: Which of the following statements about nateglinide is correct?

A. It is a long-acting oral hypoglycemic drug
B. It can be used in patients with renal impairment with caution.
C. It acts by blocking K+ channels in pancreatic beta-cells.
D. Taken just before a meal, it limits postprandial hyperglycemia in type 2 diabetes mellitus (Correct Answer)

Explanation: ***Correct: Taken just before a meal, it limits postprandial hyperglycemia in type 2 diabetes mellitus*** - **Nateglinide** is a **meglitinide analog** designed to stimulate rapid, short-duration insulin release - Specifically taken **just before meals** (preprandially) to manage postprandial glucose spikes - Its **rapid onset** (within 20 minutes) and **short duration** (approximately 4 hours) make it ideal for controlling **postprandial hyperglycemia** in type 2 diabetes - This is the **primary clinical indication** and most characteristic feature of nateglinide *Incorrect: It is a long-acting oral hypoglycemic drug* - Nateglinide is actually a **short-acting** oral hypoglycemic, not long-acting - Peak action occurs within **1 hour** and duration is only **3-4 hours** - This short duration distinguishes it from sulfonylureas like **glimepiride** or **glibenclamide** which have longer durations *Incorrect: It can be used in patients with renal impairment with caution* - Nateglinide is **hepatically metabolized** but its metabolites are **renally excreted** - Requires **dose adjustment** in moderate to severe renal impairment (CrCl <30 mL/min) - **Repaglinide** (another meglitinide) is preferred in renal impairment due to predominantly biliary excretion - Not the safest or most characteristic feature of nateglinide *Incorrect: It acts by blocking K+ channels in pancreatic beta-cells* - While nateglinide does **close ATP-dependent K+ channels** on pancreatic beta-cells (leading to depolarization and insulin release), this mechanism is **shared by all sulfonylureas and meglitinides** - This is not a **distinguishing feature** of nateglinide specifically - The question asks what is correct "about nateglinide" - while mechanistically true, this doesn't distinguish it from other insulin secretagogues

Question 790: Which of the following medications is not associated with causing hyperprolactinemia?

A. Haloperidol
B. Trifluoperazine
C. Metoclopramide
D. Lasix (Correct Answer)

Explanation: ***Lasix*** - **Furosemide (Lasix)** is a loop diuretic primarily used to treat **edema** and **hypertension**. It acts on the kidneys to increase urine output and is not known to directly affect prolactin secretion pathways. - Its mechanism of action involves inhibiting the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle, a process unrelated to dopamine or prolactin regulation. *Metoclopramide* - **Metoclopramide** is a **dopamine D2 receptor antagonist** that can readily cross the blood-brain barrier, leading to increased prolactin secretion by blocking the inhibitory effect of dopamine on prolactin release from the pituitary gland. - It is often used as an **antiemetic** and **prokinetic agent**, and hyperprolactinemia is a common side effect. *Haloperidol* - **Haloperidol** is a potent **first-generation antipsychotic** that significantly blocks **dopamine D2 receptors** in the central nervous system. - This blockade directly inhibits the dopamine-mediated suppression of prolactin, leading to a dose-dependent increase in serum prolactin levels. *Trifluoperazine* - **Trifluoperazine** is another **first-generation antipsychotic** that also acts as a potent **dopamine D2 receptor antagonist**. - Its strong dopamine D2 receptor blockade frequently results in **hyperprolactinemia**, a common side effect of typical antipsychotics.

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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