Endocrine Pharmacology Practice Questions

Q: Which is a short-acting glucocorticoid?

Hydrocortisone. **Explanation:** Glucocorticoids are classified based on their duration of action, which correlates with their biological half-life and anti-inflammatory potency. **1. Why Hydrocortisone is correct:** **Hydrocortisone (Cortisol)** is the prototypical **short-acting** glucocorticoid. It has a biological half-life of **8–12 hours**. It possesses equal glucocorticoid (anti-inflammatory) and mineralocorticoid (salt-retaining) potency (1:1 ratio). Due to its short duration and balanced profile, it is the drug of choice for replacement therapy in adrenal insufficiency (Addison’s disease). **2. Analysis of Incorrect Options:** * **Dexamethasone:** This is a **long-acting** glucocorticoid with a biological half-life of **36–72 hours**. It is highly potent, has zero mineralocorticoid activity, and is used for cerebral edema and the Dexamethasone Suppression Test. * **Fludrocortisone:** This is a synthetic mineralocorticoid with very high salt-retaining potency. While it has some glucocorticoid activity, it is classified and used clinically as a **mineralocorticoid** for replacement in Addison’s disease. * **Aldosterone:** This is the primary endogenous **mineralocorticoid** produced by the zona glomerulosa. It has negligible glucocorticoid activity and a very short half-life (approx. 20 minutes), making it unsuitable for therapeutic use as a glucocorticoid. **High-Yield NEET-PG Pearls:** * **Short-acting (8–12h):** Hydrocortisone, Cortisone. * **Intermediate-acting (12–36h):** Prednisolone, Methylprednisolone, Triamcinolone. * **Long-acting (36–72h):** Dexamethasone, Betamethasone. * **Potency Tip:** Dexamethasone is ~25 times more potent as an anti-inflammatory than Hydrocortisone. * **Pregnancy:** Prednisolone is preferred in pregnancy as it is inactivated by placental 11β-HSD2; Betamethasone/Dexamethasone are used to accelerate **fetal lung maturity** as they cross the placenta.

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

Cabergoline. **Explanation:** **Cabergoline** is the correct answer because it is a potent, synthetic ergoline derivative with a very high affinity for **D2 receptors** and an exceptionally long half-life (approximately **65–110 hours**). This long duration of action allows for convenient **once or twice-weekly dosing**, making it the preferred agent for treating hyperprolactinemia and prolactinomas. **Analysis of Incorrect Options:** * **Bromocriptine (Option A):** An older ergoline derivative and D2 agonist. It has a short half-life (about 2–8 hours) and requires daily dosing (usually 2–3 times a day). It is more commonly associated with GI side effects compared to Cabergoline. * **Lisuride (Option B):** An ergoline derivative that acts as a dopamine agonist. It has a very short half-life (approx. 2 hours) and is rarely used clinically now due to the availability of superior long-acting agents. * **Apomorphine (Option C):** A non-ergoline dopamine agonist with a very rapid onset but a very short duration of action (half-life ~40 minutes). It is used as a "rescue" medication via subcutaneous injection for "off" episodes in advanced Parkinson’s disease. **NEET-PG High-Yield Pearls:** * **Drug of Choice:** Cabergoline is the DOC for **Prolactinoma** due to better efficacy and tolerability than Bromocriptine. * **Ergot vs. Non-Ergot:** Bromocriptine and Cabergoline are **Ergot derivatives** (risk of pulmonary/cardiac fibrosis). Pramipexole and Ropinirole are **Non-ergot derivatives** (preferred in Parkinson’s to avoid fibrosis). * **Side Effects:** Dopamine agonists can cause impulse control disorders (pathological gambling, hypersexuality) and sudden sleep attacks.

Q: Which corticosteroid has the maximum sodium-retaining potential?

Aldosterone. **Explanation:** The question tests the understanding of the relative mineralocorticoid (sodium-retaining) versus glucocorticoid (anti-inflammatory) potencies of various steroids. **1. Why Aldosterone is Correct:** Aldosterone is the primary endogenous **mineralocorticoid** synthesized in the zona glomerulosa of the adrenal cortex. Its physiological role is to promote sodium and water reabsorption and potassium excretion in the distal convoluted tubule and collecting ducts of the kidney. On a comparative scale, if Cortisol has a sodium-retaining potency of 1, Aldosterone has a potency of **3000**, making it the most potent sodium-retaining steroid among the options. **2. Why the Other Options are Incorrect:** * **Dexamethasone & Betamethasone:** These are long-acting, highly potent **pure glucocorticoids**. They have a sodium-retaining potency of **zero**. This makes them ideal for conditions where fluid retention must be avoided (e.g., cerebral edema). * **Prednisolone:** This is an intermediate-acting glucocorticoid with mild mineralocorticoid activity (potency of **0.8** relative to Cortisol). While it causes some sodium retention, it is significantly weaker than Aldosterone. **3. High-Yield Clinical Pearls for NEET-PG:** * **Fludrocortisone:** This is the most potent *synthetic* mineralocorticoid (potency ~125-250) and is the drug of choice for replacement therapy in Addison’s disease. * **Potency Ratio:** Dexamethasone is the most potent anti-inflammatory steroid (25-30 times more than cortisol) but has no mineralocorticoid effect. * **DOCA (Desoxycorticosterone acetate):** Another pure mineralocorticoid, but unlike Aldosterone, it lacks glucocorticoid activity entirely. * **Rule of Thumb:** As glucocorticoid potency increases in synthetic steroids (Prednisolone → Betamethasone), mineralocorticoid activity typically decreases.

Q: Which drug is used to suppress lactation?

Bromocriptine. **Explanation:** Lactation is primarily regulated by the hormone **Prolactin**, which is secreted by the anterior pituitary. Prolactin secretion is under tonic inhibition by **Dopamine** (also known as Prolactin Inhibiting Factor). **1. Why Bromocriptine is Correct:** Bromocriptine is a potent **Dopamine (D2) receptor agonist**. By mimicking the action of dopamine, it inhibits the release of prolactin from the pituitary gland. Without prolactin, milk production (lactogenesis) is suppressed. It is clinically used for lactation suppression in cases of stillbirth, neonatal death, or medical contraindications to breastfeeding. **2. Why the other options are incorrect:** * **Metoclopramide & Domperidone:** These are **Dopamine antagonists**. By blocking dopamine receptors, they remove the inhibitory effect on prolactin, leading to *increased* prolactin levels. These drugs are sometimes used as galactagogues to increase milk supply, not suppress it. * **Prolactin:** This is the hormone responsible for milk production. Administering prolactin would promote lactation rather than suppress it. **NEET-PG High-Yield Pearls:** * **Drug of Choice:** While Bromocriptine is the classic answer, **Cabergoline** (a long-acting dopamine agonist) is now the preferred drug for lactation suppression due to its superior efficacy and fewer side effects (less nausea/hypotension). * **Physiological Suppression:** The most common cause of lactation suppression is the cessation of suckling, which leads to breast engorgement and feedback inhibition of milk secretion. * **Estrogen's Role:** During pregnancy, high levels of Estrogen and Progesterone inhibit the action of prolactin on the breast. Lactation only begins postpartum when these steroid levels drop.

Q: Which antithyroid drug is contraindicated in pregnancy?

Radioactive Iodine (131I). **Explanation:** **1. Why Radioactive Iodine (131I) is the Correct Answer:** Radioactive Iodine (131I) is **absolutely contraindicated** in pregnancy (FDA Category X). Iodine-131 crosses the placenta and is concentrated by the fetal thyroid gland after the 10th–12th week of gestation. This leads to permanent **fetal thyroid ablation**, resulting in congenital hypothyroidism, mental retardation, and an increased risk of childhood malignancies. A pregnancy test is mandatory before administering 131I to any woman of reproductive age. **2. Analysis of Incorrect Options:** * **Propylthiouracil (PTU):** This is the **drug of choice in the 1st trimester**. It is preferred because it is more highly protein-bound than Methimazole, leading to less placental transfer. It also avoids the specific teratogenic risks associated with Methimazole. * **Methimazole (MMI):** While generally avoided in the 1st trimester due to risks of **Aplasia Cutis** (congenital skin defects) and **Choanal/Esophageal atresia**, it is the **preferred drug in the 2nd and 3rd trimesters** because PTU carries a higher risk of maternal hepatotoxicity. * **Carbimazole:** This is a prodrug of Methimazole. It carries the same teratogenic profile as Methimazole and is avoided in early pregnancy. **3. NEET-PG High-Yield Pearls:** * **1st Trimester Choice:** Propylthiouracil (PTU). * **2nd/3rd Trimester Choice:** Methimazole (MMI). * **Mechanism of PTU:** Inhibits Thyroid Peroxidase (TPO) AND peripheral conversion of T4 to T3 (MMI does not inhibit peripheral conversion). * **Breastfeeding:** Both PTU and MMI are considered safe in moderate doses, though MMI is often preferred here to avoid maternal liver issues. * **Thyroid Storm:** PTU is preferred due to its dual action (inhibiting synthesis and peripheral conversion).

Q: All of the following statements regarding T3 (Tri-iodothyronine) are true EXCEPT?

T3 is usually given as 100 mg once daily.. **Explanation:** The correct answer is **C** because it contains two significant pharmacological errors: the **dosage unit** and the **frequency**. T3 (Liothyronine) is highly potent; the standard replacement dose is measured in **micrograms (mcg)**, not milligrams (mg). Furthermore, due to its short half-life, it requires **multiple daily dosing** (2–3 times a day) rather than once-daily administration to maintain stable plasma levels. **Analysis of other options:** * **Option A (True):** T3 has a very short half-life of approximately **18–24 hours** (compared to 7 days for T4). This necessitates frequent dosing and makes it less ideal for routine maintenance therapy. * **Option B (True):** The thyroid gland primarily secretes T4. Only about **20%** of circulating T3 is secreted directly by the thyroid; the remaining **80%** is generated via peripheral deiodination. * **Option D (True):** T3 is the **physiologically active** form. It has a 3–5 times higher affinity for nuclear thyroid receptors than T4. T4 acts largely as a pro-hormone that undergoes peripheral conversion by the enzyme **5'-deiodinase**. **High-Yield NEET-PG Pearls:** * **Drug of Choice:** Levothyroxine (T4) is the drug of choice for hypothyroidism due to its long half-life, low cost, and stable serum levels. * **Myxedema Coma:** While IV Levothyroxine is standard, **IV Liothyronine (T3)** is preferred in some protocols for faster onset of action in life-threatening cases. * **Deiodination Inhibitors:** Drugs like **Propylthiouracil (PTU), Propranolol, and Glucocorticoids** inhibit the peripheral conversion of T4 to T3, which is why they are used in managing Thyroid Storm.

Question 1

Which is a short-acting glucocorticoid?

Accepted Answer

Hydrocortisone

Answer

Fludrocortisone

Answer

Dexamethasone

Answer

Aldosterone

Question 2

Which of the following drugs can be used to suppress lactation?

Accepted Answer

Metoclopramide

Answer

Cabergoline

Answer

Pyridoxine

Answer

High dose estrogens

Question 3

Which of the following is a long-acting dopamine agonist?

Accepted Answer

Cabergoline

Answer

Bromocriptine

Answer

Lisuride

Answer

Apomorphine

Question 4

Which corticosteroid has the maximum sodium-retaining potential?

Accepted Answer

Aldosterone

Answer

Dexamethasone

Answer

Prednisolone

Answer

Betamethasone

Question 5

Danazol is useful in the treatment of all the following conditions EXCEPT?

Accepted Answer

Hirsutism

Answer

Endometriosis

Answer

Dysfunctional uterine bleeding (DUB)

Answer

Leiomyoma

Question 6

Which drug is used to suppress lactation?

Accepted Answer

Bromocriptine

Answer

Metoclopramide

Answer

Domperidone

Answer

Prolactin

Question 7

A patient with severe shoulder pain resulting from inflammation is not responding to treatment with naproxen. Treatment with oral dexamethasone was initiated. What is the basis for the glucocorticoid being more effective as an anti-inflammatory agent?

Accepted Answer

Glucocorticoids inhibit both prostaglandin production and inflammatory cells.

Answer

Glucocorticoids inhibit the biosynthesis of both COX-1 and COX-2.

Answer

Glucocorticoids will reduce the edema in the inflamed area.

Answer

Glucocorticoids are more potent inhibitors of cyclooxygenase than naproxen.

Question 8

Which antithyroid drug is contraindicated in pregnancy?

Accepted Answer

Radioactive Iodine (131I)

Answer

Propylthiouracil

Answer

Methimazole

Answer

Carbimazole

Question 9

All of the following statements regarding T3 (Tri-iodothyronine) are true EXCEPT?

Accepted Answer

T3 is usually given as 100 mg once daily.

Answer

Half-life of T3 is only a few hours.

Answer

Only 20% of the total T3 is produced by the thyroid.

Answer

T3 is the active form of the hormone and is produced in the periphery by conversion from T4.

Question 10

Which intra-articular steroid is least preferred in osteoarthritis?

Accepted Answer

Prednisolone

Answer

Triamcinolone

Answer

Hydrocortisone

Answer

Betamethasone

Endocrine Pharmacology — MCQs

Endocrine Pharmacology — MCQs

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