Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 611: What is the most potent mineralocorticoid?

A. Aldosterone (Correct Answer)
B. Deoxycorticosterone (DOCA)
C. Fludrocortisone
D. Triamcinolone

Explanation: **Explanation:** **Aldosterone** is the correct answer because it is the primary and most potent endogenous mineralocorticoid produced by the *zona glomerulosa* of the adrenal cortex. It plays a critical role in electrolyte balance by acting on the distal convoluted tubules and collecting ducts to promote sodium reabsorption and potassium/hydrogen excretion. **Analysis of Options:** * **Aldosterone (A):** It is the physiological gold standard for mineralocorticoid activity. While it has the highest potency, it is not used clinically for replacement therapy because it has poor oral bioavailability and a very short half-life. * **Deoxycorticosterone (DOCA) (B):** This is a precursor to aldosterone. While it possesses significant mineralocorticoid activity, its potency is much lower than that of aldosterone. * **Fludrocortisone (C):** This is a synthetic corticosteroid. While it is the **most potent mineralocorticoid used clinically** (due to its high oral efficacy), its intrinsic mineralocorticoid receptor affinity is still less than that of endogenous aldosterone. * **Triamcinolone (D):** This is a selective intermediate-acting **glucocorticoid**. It is specifically designed to have virtually zero mineralocorticoid activity, making it useful when fluid retention must be avoided. **NEET-PG High-Yield Pearls:** * **Potency Hierarchy:** Aldosterone > Fludrocortisone > DOCA. * **Clinical Use:** Fludrocortisone is the drug of choice for mineralocorticoid replacement in Addison’s disease. * **Spironolactone:** The primary antagonist used to block these potent effects in conditions like Conn’s syndrome (primary hyperaldosteronism). * **Glucocorticoid with least mineralocorticoid activity:** Dexamethasone and Betamethasone (Zero mineralocorticoid effect).

Question 612: Which insulin formulation is never mixed with other insulins?

A. Utile
B. Aspa
C. Lispro
D. Glargine (Correct Answer)

Explanation: **Explanation:** **1. Why Glargine is the Correct Answer:** Insulin Glargine is a long-acting basal insulin analog with a unique pharmacokinetic profile. It is formulated at an **acidic pH (pH 4.0)** to remain completely soluble in its vial. When injected subcutaneously, the neutral pH of the body causes the glargine molecules to precipitate into **microprecipitates**. These precipitates slowly dissolve over 24 hours, providing a "peakless" steady release. If Glargine is mixed with other insulins (which are generally formulated at a neutral pH of 7.0–7.4), the acidic pH is altered. This causes the Glargine to precipitate prematurely in the syringe, unpredictably changing its absorption rate and duration of action, thereby losing its basal profile. **2. Why Other Options are Incorrect:** * **B & C (Aspart and Lispro):** These are rapid-acting insulin analogs. They are formulated at a neutral pH and are frequently mixed with intermediate-acting NPH (Neutral Protamine Hagedorn) insulin in the same syringe for "split-mixed" regimens. * **A (Ultralente):** This is an older, long-acting crystalline insulin. While less common now, it was historically compatible with regular insulin. **3. High-Yield Clinical Pearls for NEET-PG:** * **The "Clear before Cloudy" Rule:** When mixing NPH (cloudy) with Regular/Rapid insulin (clear), always draw the clear insulin first to prevent contaminating the clear vial with protamine. * **Detemir Exception:** While Glargine is strictly never mixed, Insulin Detemir (another long-acting analog) is also generally recommended to be administered alone, though the pH-based contraindication is most classic for Glargine. * **Site of Injection:** Abdomen has the fastest absorption, followed by the arm, thigh, and buttock. * **Most common side effect:** Hypoglycemia; **Most common local side effect:** Lipodystrophy (prevented by rotating injection sites).

Question 613: Which of the following is true about diazoxide, except?

A. Potassium channel opener
B. Can be used as an antihypertensive agent
C. Causes severe hypoglycemia (Correct Answer)
D. Used in insulinoma

Explanation: **Explanation:** **Diazoxide** is a unique pharmacological agent that acts as a **potassium channel opener** (specifically the $K_{ATP}$ channels) in both vascular smooth muscle and pancreatic beta cells. 1. **Why Option C is the correct answer (The Exception):** Diazoxide does **not** cause hypoglycemia; instead, it causes **hyperglycemia**. By opening $K_{ATP}$ channels in the pancreatic beta cells, it hyperpolarizes the cell membrane, which inhibits the release of insulin. Because it reduces insulin secretion, it is used to treat hypoglycemia, not cause it. 2. **Analysis of Other Options:** * **Option A (Potassium channel opener):** This is its primary mechanism of action. By keeping $K^+$ channels open, it stabilizes the resting membrane potential and prevents depolarization. * **Option B (Antihypertensive agent):** In vascular smooth muscle, opening $K^+$ channels leads to hyperpolarization and relaxation, causing potent vasodilation. Although rarely used now due to newer drugs, it was historically used intravenously for hypertensive emergencies. * **Option D (Used in insulinoma):** Because it inhibits insulin release, it is the medical treatment of choice for managing hypoglycemia in patients with inoperable insulinomas or leucine-sensitive hypoglycemia. **High-Yield Clinical Pearls for NEET-PG:** * **Side Effects:** The most notable side effect of chronic diazoxide use is **hypertrichosis** (excessive hair growth), similar to minoxidil (another $K^+$ channel opener). * **Fluid Retention:** It can cause significant sodium and water retention, often requiring co-administration of diuretics. * **Mnemonic:** Remember **"Diaz-Oxide Opens"** (Opens $K^+$ channels $\rightarrow$ Stops Insulin $\rightarrow$ Increases Glucose).

Question 614: Which of the following drugs is used in the management of diabetes mellitus?

A. Bromocriptine (Correct Answer)
B. Octreotide
C. Prednisolone
D. Pegvisomant

Explanation: **Explanation:** **Bromocriptine (Option A)** is a dopamine D2 receptor agonist traditionally used for Parkinson’s disease and hyperprolactinemia [1]. However, a specific **quick-release (QR) formulation** of Bromocriptine is FDA-approved for the management of Type 2 Diabetes Mellitus. * **Mechanism:** It acts on the circadian rhythm in the hypothalamus to reset abnormally low dopaminergic tone in the morning. This leads to a reduction in hepatic glucose production, decreased insulin resistance, and lower free fatty acid levels without increasing insulin secretion. **Analysis of Incorrect Options:** * **B. Octreotide:** A somatostatin analogue used for acromegaly and secretory diarrheas. It actually **inhibits insulin release** and can potentially worsen glycemic control or cause hypoglycemia/hyperglycemia. * **C. Prednisolone:** A glucocorticoid that is notoriously **diabetogenic**. It increases gluconeogenesis and causes peripheral insulin resistance, often leading to steroid-induced diabetes. * **D. Pegvisomant:** A growth hormone receptor antagonist used specifically for **acromegaly** that does not respond to other treatments. **High-Yield Clinical Pearls for NEET-PG:** * **Bromocriptine QR** is the only dopaminergic drug approved for T2DM [2]. It is weight-neutral and has a low risk of hypoglycemia. * Other "non-traditional" drugs for T2DM include **Colesevelam** (a bile acid sequestrant) [3]. * **Side Effects of Bromocriptine:** Nausea, dizziness, and orthostatic hypotension are common during initiation. * **Contraindication:** It should not be used in patients with syncopal migraines or those nursing (as it inhibits prolactin).

Question 615: Among the following, which 5-PDE inhibitor has the longest duration of action?

A. Sildenafil
B. Vardenafil
C. Tadalafil (Correct Answer)
D. Udenafil

Explanation: ### Explanation **Correct Option: C. Tadalafil** The duration of action of Phosphodiesterase-5 (PDE-5) inhibitors is primarily determined by their elimination half-life. **Tadalafil** is unique among this class because it has a significantly longer half-life (approximately 17.5 hours) compared to its counterparts [1]. This results in a duration of action that can extend up to **36 hours**, earning it the nickname **"The Weekend Pill."** The underlying medical concept involves the inhibition of PDE-5, which prevents the breakdown of cGMP in the corpus cavernosum, leading to smooth muscle relaxation and prolonged vasodilation [1]. Tadalafil’s long duration allows for greater spontaneity in sexual activity and is also why it is preferred for daily low-dose administration in Benign Prostatic Hyperplasia (BPH) [1]. **Analysis of Incorrect Options:** * **A. Sildenafil:** The first-in-class PDE-5 inhibitor. It has a short half-life (4 hours) and a duration of action of about 4–6 hours [1]. Its absorption is significantly delayed by fatty meals. * **B. Vardenafil:** Similar to Sildenafil in terms of pharmacokinetics, it has a half-life of 4–5 hours and a duration of action of approximately 5–8 hours. * **D. Udenafil:** This is a newer agent with an intermediate duration. Its half-life is roughly 11–13 hours, making it longer-acting than Sildenafil but still shorter than Tadalafil. **High-Yield Clinical Pearls for NEET-PG:** 1. **Food Interaction:** Tadalafil is the only PDE-5 inhibitor whose absorption is **not affected by food**. Sildenafil and Vardenafil should be taken on an empty stomach. 2. **Side Effects:** Tadalafil is associated with **back pain and myalgia** due to PDE-11 inhibition (found in skeletal muscle). 3. **Vision Changes:** Sildenafil can cause "Blue Vision" (cyanopsia) due to cross-reactivity with PDE-6 in the retina. 4. **Absolute Contraindication:** All PDE-5 inhibitors are contraindicated in patients taking **Nitrates**, as the combination can cause life-threatening hypotension [1].

Question 616: Which of the following agents is useful for the oral treatment of both pituitary and renal diabetes insipidus?

A. Vasopressin
B. Hydrochlorothiazide (Correct Answer)
C. Chlorpropamide
D. Carbamazepine

Explanation: ### Explanation **Correct Option: B. Hydrochlorothiazide** Hydrochlorothiazide (a thiazide diuretic) is the only agent among the options that is effective in both **Central (Pituitary)** and **Nephrogenic (Renal)** Diabetes Insipidus (DI). * **Mechanism:** While it seems counterintuitive to use a diuretic for polyuria, thiazides induce a state of mild volume depletion. This leads to a compensatory increase in proximal convoluted tubule (PCT) reabsorption of sodium and water, resulting in less fluid delivery to the distal nephron and a reduction in total urine volume. Because this mechanism is independent of ADH receptors, it works even when the kidneys are resistant to ADH (Nephrogenic DI). **Analysis of Incorrect Options:** * **A. Vasopressin:** This is exogenous ADH. It is highly effective for Central DI (replacement therapy) but is **ineffective** in Renal DI because the pathology in the latter is end-organ resistance to ADH. Furthermore, it is not administered orally. * **C. Chlorpropamide:** A sulfonylurea that increases the sensitivity of the kidney to ADH and stimulates ADH release. It is only useful in **Central DI** where some residual ADH is present. * **D. Carbamazepine:** An anticonvulsant that stimulates ADH release from the pituitary. Like chlorpropamide, it is only effective in **Central DI**. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC):** For Central DI, the DOC is **Desmopressin** (V2 selective, administered intranasally or orally). * **DOC for Nephrogenic DI:** Thiazides or Amiloride. * **Lithium-Induced DI:** Amiloride is the specific treatment of choice as it blocks the ENaC channels through which lithium enters the collecting duct cells. * **Paradoxical Effect:** The use of thiazides in DI is often referred to as a "paradoxical" reduction in urine output.

Question 617: Which of the following is a long-acting insulin?

A. Insulin glargine (Correct Answer)
B. Insulin lispro
C. Insulin aspart
D. Insulin glulisine

Explanation: **Explanation:** Insulin preparations are classified based on their onset and duration of action. Understanding this classification is crucial for managing diabetes mellitus and is a high-yield topic for NEET-PG. **1. Why Insulin Glargine is Correct:** **Insulin glargine** is a **long-acting (basal) insulin** analog. It is designed to have low solubility at physiological pH. When injected subcutaneously, it forms micro-precipitates that release insulin slowly into the bloodstream. This results in a relatively "peakless" profile with a duration of action lasting approximately 24 hours, mimicking the steady basal secretion of insulin from a healthy pancreas. **2. Why the Other Options are Incorrect:** * **Insulin Lispro, Aspart, and Glulisine (Options B, C, and D):** These are all **rapid-acting insulin analogs**. They are designed to dissociate rapidly into monomers after injection, leading to a quick onset (15–30 mins) and a short duration of action (3–5 hours). They are typically used as "bolus" or "prandial" insulin to control post-meal glucose spikes. **3. High-Yield Clinical Pearls for NEET-PG:** * **The "L" Rule:** Remember **L**ong-acting insulins: **L**antus (Glargine), **L**evemir (Detemir), and Deg**l**udec. * **Degludec:** This is an "ultra-long-acting" insulin with a duration of action exceeding 40 hours. * **Mixing:** Insulin glargine should **not** be mixed in the same syringe with other insulins because its acidic pH (pH 4.0) can cause the other insulins to precipitate. * **Afrezza:** This is a rapid-acting **inhaled** insulin, contraindicated in smokers and COPD patients.

Question 618: Dapoxetine is specifically developed for what condition?

A. Depression
B. Psychosis
C. Premature ejaculation (Correct Answer)
D. Anxiety disorder

Explanation: **Explanation:** **Dapoxetine** is a unique, short-acting **Selective Serotonin Reuptake Inhibitor (SSRI)** specifically designed and FDA-approved for the treatment of **Premature Ejaculation (PE)** in men aged 18–64 years. **1. Why Premature Ejaculation is Correct:** While most SSRIs are used for psychiatric disorders, they are known to cause "delayed ejaculation" as a side effect by increasing serotonin levels at the post-synaptic cleft, which inhibits the ejaculatory reflex. Dapoxetine was engineered to exploit this effect. Unlike fluoxetine or paroxetine, which have long half-lives, Dapoxetine is **rapidly absorbed and rapidly eliminated** (peak plasma concentration in 1 hour). This pharmacokinetic profile makes it ideal for **"on-demand"** dosing (taken 1–3 hours before intercourse) without causing the long-term systemic accumulation seen with antidepressants. **2. Why Other Options are Incorrect:** * **A & D (Depression and Anxiety):** Although Dapoxetine is an SSRI, its rapid clearance makes it ineffective for maintaining the steady-state neurotransmitter levels required to treat mood or anxiety disorders. * **B (Psychosis):** Psychosis is primarily managed with Dopamine (D2) receptor antagonists (Antipsychotics), not SSRIs. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Inhibits serotonin transporter (SERT), increasing serotonin action at the pre-synaptic and post-synaptic receptors involved in the ejaculatory delay. * **Pharmacokinetics:** Shortest half-life among SSRIs (~1.5 hours). * **Contraindications:** Should not be used with potent CYP3A4 inhibitors or in patients with significant heart failure/permanent pacemaker dependency. * **Common Side Effects:** Nausea, dizziness, and headache.

Question 619: All of the following are true about estrogen, EXCEPT:

A. Causes cholestasis
B. Used in the treatment of gynecomastia (Correct Answer)
C. Used in H
D. Increased risk of breast cancer

Explanation: **Explanation:** The correct answer is **B. Used in the treatment of gynecomastia.** **Why Option B is the Exception:** Gynecomastia is the enlargement of glandular breast tissue in males, typically caused by an imbalance between estrogen and androgen actions (increased estrogen or decreased testosterone). Administering estrogen would **worsen** or even cause gynecomastia, not treat it. In fact, estrogen therapy (used in prostate cancer) is a well-known cause of this condition. Treatment usually involves Selective Estrogen Receptor Modulators (SERMs) like **Tamoxifen**, which block estrogen receptors in breast tissue. **Analysis of Other Options:** * **A. Causes cholestasis:** Estrogens decrease the activity of the bile salt export pump (BSEP) and increase cholesterol secretion into bile, leading to cholestasis and an increased risk of gallstones. * **C. Used in HRT (Hormone Replacement Therapy):** Estrogen is a cornerstone of HRT for managing postmenopausal symptoms (vasomotor instability, vaginal atrophy) and preventing osteoporosis. * **D. Increased risk of breast cancer:** Prolonged exposure to estrogen (especially when unopposed by progesterone) is a documented risk factor for breast and endometrial cancers due to its proliferative effects on these tissues. **High-Yield Clinical Pearls for NEET-PG:** * **Metabolic Effects:** Estrogens increase HDL and decrease LDL (cardioprotective) but increase triglycerides. * **Coagulation:** They increase the synthesis of clotting factors (II, VII, IX, X) and decrease Antithrombin III, increasing the risk of **Thromboembolism**. * **Contraindications:** Estrogen should be avoided in patients with a history of undiagnosed vaginal bleeding, estrogen-dependent tumors, or active thromboembolic disease.

Question 620: Which of the following insulins can be administered intravenously?

A. Protamine zinc insulin
B. Ultra lente insulin
C. Semi lente insulin
D. Regular insulin (Correct Answer)

Explanation: **Explanation:** **Regular (Soluble) Insulin** is the only conventional insulin that can be administered intravenously. This is because it is a clear, buffered solution of crystalline zinc insulin. When injected IV, it has an immediate onset of action and a very short half-life (approx. 5–10 minutes), making it the gold standard for managing medical emergencies like **Diabetic Ketoacidosis (DKA)**, Hyperosmolar Hyperglycemic State (HHS), and during perioperative care where rapid titration is required. **Why the other options are incorrect:** * **Protamine Zinc Insulin (PZI):** This is a long-acting insulin where insulin is complexed with protamine. It is a suspension, and injecting suspensions intravenously can cause **embolism** and unpredictable absorption. * **Ultra Lente and Semi Lente:** These are "Lente" series insulins (now largely obsolete) that contain varying sizes of zinc-insulin crystals to delay absorption. Like PZI, these are **cloudy suspensions** and are strictly meant for subcutaneous administration only. **High-Yield NEET-PG Pearls:** 1. **Rapid-acting analogs:** While Insulin **Lispro, Aspart, and Glulisine** can also be given IV, Regular insulin remains the preferred and most cost-effective choice for IV infusions. 2. **Route of Administration:** All insulins are given **Subcutaneously (SC)** for routine maintenance. Only Regular insulin is routinely used **IV/IM**. 3. **Appearance:** A quick clinical rule—**"Clear before Cloudy."** Only clear insulins (Regular and rapid-acting analogs) are typically safe for IV use; cloudy insulins (NPH, Lente) are never given IV. 4. **Glut-4:** Insulin acts by translocating GLUT-4 transporters to the cell membrane in adipose tissue and skeletal muscle.

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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