Endocrine Pharmacology Practice Questions

Q: Which antidiabetic drug acts independently of insulin?

SGLT2 inhibitor. The correct answer is **A. SGLT2 inhibitor** (e.g., Dapagliflozin, Empagliflozin). **Mechanism of Action:** SGLT2 inhibitors act on the proximal convoluted tubule (PCT) of the kidney to inhibit the Sodium-Glucose Co-transporter 2. This prevents the reabsorption of filtered glucose, leading to **glycosuria** (excretion of glucose in the urine). Because this process depends entirely on the renal filtration of glucose and not on pancreatic function or peripheral insulin sensitivity, it is considered **insulin-independent**. This makes them effective even in patients with long-standing Type 2 Diabetes who have significant beta-cell exhaustion. **Why the other options are incorrect:** * **B. DPP4 inhibitors** (e.g., Sitagliptin) and **D. GLP1 agonists** (e.g., Liraglutide) are incretin-based therapies. They work by stimulating the pancreas to release insulin in a glucose-dependent manner [2]. * **C. Meglitinide analogues** (e.g., Repaglinide) are insulin secretagogues [1]. They close ATP-sensitive K+ channels in pancreatic beta cells, directly triggering insulin release [1], [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Weight Loss & BP:** SGLT2 inhibitors promote weight loss (due to calorie loss via glucose) and lower blood pressure (due to osmotic diuresis). * **Cardio-Renal Protection:** They are the drugs of choice for diabetic patients with **Heart Failure** (reduced HFrEF) and **Chronic Kidney Disease (CKD)**. * **Side Effects:** The most characteristic side effects are **Genital Mycotic Infections** (due to high urinary glucose) and a rare risk of **Euglycemic Ketoacidosis**.

Q: Which of the following agents improves pituitary diabetes insipidus?

Chlorpropamide. **Explanation:** **Pituitary Diabetes Insipidus (Central DI)** is characterized by a deficiency of Antidiuretic Hormone (ADH/Vasopressin). The goal of treatment is to either replace ADH or enhance the body's response to the little ADH remaining [1]. **Why Chlorpropamide is correct:** Chlorpropamide is a first-generation sulfonylurea primarily used for Type 2 Diabetes. However, it has a unique secondary effect: it **potentiates the action of residual ADH** on the renal collecting ducts and may also stimulate the pituitary to release more ADH. It is effective only in partial Central DI where some endogenous ADH production is still present. **Analysis of Incorrect Options:** * **A. Water restriction:** This is the treatment for Primary Polydipsia. In DI, water restriction is dangerous as it leads to severe dehydration and hypernatremia because the kidneys cannot concentrate urine [1]. * **B. Lithium:** Lithium is a well-known cause of **Nephrogenic DI**. It inhibits adenylyl cyclase in the collecting ducts, making them resistant to ADH [2]. * **C. Chlorthiazide:** While Thiazide diuretics are used to treat Nephrogenic DI (by inducing mild hypovolemia and increasing proximal sodium/water reabsorption), they are not the primary choice for Central DI. Chlorpropamide is a more classic "textbook" answer for pharmacological enhancement of ADH in Central DI. **NEET-PG High-Yield Pearls:** * **Drug of Choice (DOC) for Central DI:** Desmopressin (dDAVP) – a synthetic V2 agonist [1]. * **DOC for Nephrogenic DI:** Thiazide diuretics (e.g., Hydrochlorothiazide) and Amiloride (especially if lithium-induced). * **Other drugs for Central DI:** Carbamazepine and Clofibrate also stimulate ADH release. * **Diagnostic Test:** Water Deprivation Test followed by Desmopressin administration (Central DI shows >50% increase in urine osmolality; Nephrogenic shows little to no change) [1].

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

Insulin glargine. ### Explanation Insulin preparations are classified based on their onset and duration of action. Understanding these kinetics is crucial for NEET-PG, as it forms the basis of "Basal-Bolus" therapy. **Correct Answer: A. Insulin glargine** Insulin glargine is a **long-acting (basal) insulin analog**. It is designed with a shifted isoelectric point (by substituting asparagine with glycine and adding two arginines), making it soluble at an acidic pH but poorly soluble at the neutral pH of subcutaneous tissue. Upon injection, it forms micro-precipitates that release insulin slowly over 24 hours. It is often called "peakless" insulin because it provides a steady background level of insulin, mimicking physiological basal secretion. **Incorrect Options:** * **B, C, and D (Lispro, Aspart, Glulisine):** These are **Rapid-acting insulin analogs**. They are designed to dissociate rapidly into monomers after subcutaneous injection, leading to a quick onset (15 mins) and short duration (3–5 hours). They are used as "prandial" or "bolus" insulin to control post-prandial glucose spikes. **High-Yield Clinical Pearls for NEET-PG:** * **Ultra-long acting:** Insulin **Degludec** has the longest half-life (>40 hours) due to the formation of multi-hexamers. * **Intermediate-acting:** **NPH (Isophane)** insulin has a "cloudy" appearance and a duration of 12–18 hours. * **Safety:** Glargine should **not** be mixed in the same syringe with other insulins, as its acidic pH (4.0) can cause the other insulins to precipitate. * **Inhaled Insulin:** Afrezza is a rapid-acting dry powder formulation.

Q: What is the most potent mineralocorticoid?

Aldosterone. **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).

Q: Which insulin formulation is never mixed with other insulins?

Glargine. **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).

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

Causes severe hypoglycemia. **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 1

Which antidiabetic drug acts independently of insulin?

Accepted Answer

SGLT2 inhibitor

Answer

DPP4 inhibitor

Answer

Meglitinide analogues

Answer

GLP1 agonist

Question 2

All of the following may be used to treat hypercalcemia, except:

Accepted Answer

Normal saline with forced diuresis with thiazide

Answer

Plicamycin

Answer

Gallium nitrate

Answer

Mitramycin

Question 3

A 21-year-old student is diagnosed with hyperthyroidism and is being counselled on treatment options, including radioactive iodine and antithyroid medications. Carbimazole acts on which part of the thyroid hormone synthesis pathway?

Accepted Answer

Organification of iodide by thyroid peroxidase, incorporating it into tyrosine to form MIT and DIT

Answer

Cleavage of thyroglobulin by proteolysis

Answer

Coupling of monoiodotyrosine (MIT) and diiodotyrosine (DIT) forming triiodothyronine (T3) and thyroxine (T4)

Answer

Dehalogenation of iodinated tyrosine to recycle iodide

Question 4

Conversion of T4 to T3 is inhibited by all except:

Accepted Answer

Methimazole

Answer

Propranolol

Answer

Propylthiouracil

Answer

Amiodarone

Question 5

Which of the following agents improves pituitary diabetes insipidus?

Accepted Answer

Chlorpropamide

Answer

Water restriction

Answer

Lithium

Answer

Chlorthiazide

Question 6

What is the effect of adding progesterone to estrogens?

Accepted Answer

Decrease the occurrence of endometrial cancers

Answer

Decrease the estrogen action on the breast

Answer

Increase the effectiveness of the estrogens

Answer

Inhibit bone resorption

Question 7

Which of the following is a long-acting insulin?

Accepted Answer

Insulin glargine

Answer

Insulin lispro

Answer

Insulin aspart

Answer

Insulin glulisine

Question 8

What is the most potent mineralocorticoid?

Accepted Answer

Aldosterone

Answer

Deoxycorticosterone (DOCA)

Answer

Fludrocortisone

Answer

Triamcinolone

Question 9

Which insulin formulation is never mixed with other insulins?

Accepted Answer

Glargine

Answer

Utile

Answer

Aspa

Answer

Lispro

Question 10

Which of the following is true about diazoxide, except?

Accepted Answer

Causes severe hypoglycemia

Answer

Potassium channel opener

Answer

Can be used as an antihypertensive agent

Answer

Used in insulinoma

Endocrine Pharmacology — MCQs

Endocrine Pharmacology — MCQs

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