Endocrine Pharmacology Practice Questions

Q: Cinacalcet acts by which of the following mechanisms?

Decreasing parathyroid hormone secretion. **Mechanism of Action** Cinacalcet is a **calcimimetic** agent. It works by increasing the sensitivity of **calcium-sensing receptors (CaSR)** located on the chief cells of the parathyroid gland to extracellular calcium. By mimicking the action of calcium, it "tricks" the gland into sensing that calcium levels are high, thereby suppressing the synthesis and release of **Parathyroid Hormone (PTH)**. **Analysis of Options** * **Option A (Inhibiting RANK-ligand):** This is the mechanism of **Denosumab**, a monoclonal antibody used in osteoporosis to prevent osteoclast maturation. * **Option B (Activating osteoblasts):** Teriparatide (recombinant PTH 1-34) acts as an anabolic agent by stimulating osteoblasts when given in intermittent doses. * **Option D (Increasing Vitamin D levels):** Vitamin D analogs (like Calcitriol or Paricalcitol) are used to suppress PTH, but Cinacalcet does not increase Vitamin D; in fact, it is often used alongside Vitamin D sterols. **Clinical Pearls for NEET-PG** * **Indications:** Secondary hyperparathyroidism in Chronic Kidney Disease (CKD) on dialysis and Parathyroid Carcinoma. * **Side Effects:** The most common side effect is **hypocalcemia** (since it lowers PTH) and GI upset (nausea/vomiting). * **Etelcalcetide:** A newer intravenous calcimimetic that also targets the CaSR. * **Key Distinction:** Unlike Vitamin D analogs, Cinacalcet lowers PTH without increasing intestinal absorption of calcium and phosphorus, making it ideal for patients with high calcium-phosphorus products.

Q: All of the following are true regarding adverse effects of chlorpropamide except?

Less incidence of hypoglycemia. **Explanation:** Chlorpropamide is a **first-generation sulfonylurea** used in the management of Type 2 Diabetes Mellitus. Understanding its unique pharmacokinetic profile is key to identifying its adverse effects. **Why Option B is the Correct Answer:** Chlorpropamide has an exceptionally **long half-life (approx. 32–36 hours)** and is excreted slowly by the kidneys. Because of its prolonged duration of action, it actually carries a **higher incidence of severe and prolonged hypoglycemia** compared to other sulfonylureas, especially in elderly patients or those with renal impairment. Therefore, the statement "Less incidence of hypoglycemia" is false. **Analysis of Other Options:** * **A. Releases ADH:** Chlorpropamide is unique among sulfonylureas because it increases the secretion of Antidiuretic Hormone (ADH) and enhances the sensitivity of renal tubules to ADH. This can lead to **SIADH** and **dilutional hyponatremia**. * **C. More incidence of weight gain:** Like all sulfonylureas, chlorpropamide stimulates insulin release. Insulin is an anabolic hormone that promotes lipogenesis, leading to weight gain as a common side effect. * **D. Disulfiram-like reaction:** Chlorpropamide can inhibit aldehyde dehydrogenase. If a patient consumes alcohol while on this medication, they may experience flushing, nausea, and tachycardia (the **Disulfiram-like reaction**). **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for DI?** Chlorpropamide was historically used in **Partial Central Diabetes Insipidus** due to its ADH-potentiating effect. * **The "C" Rule:** Remember **C**hlorpropamide causes **C**onfusion (due to hyponatremia), **C**holestatic jaundice, and **C**hlorpropamide-alcohol flush. * **Avoid in Elderly:** Due to the high risk of prolonged hypoglycemia and hyponatremia, it is generally avoided in geriatric populations (Beers Criteria).

Q: Which selective V2 receptor agonist is useful for the treatment of central diabetes insipidus?

Desmopressin. **Explanation:** **Desmopressin (dDAVP)** is the drug of choice for **Central Diabetes Insipidus (CDI)**. It is a synthetic analogue of Vasopressin (ADH) with two specific modifications: deamination of cysteine and substitution of L-arginine with D-arginine. These changes result in a **selective V2 receptor agonist** profile with minimal V1 (vasoconstrictor) activity. By acting on V2 receptors in the renal collecting ducts, it increases water reabsorption via aquaporin-2 channels. It also has a longer duration of action (6–24 hours) compared to natural ADH. **Analysis of Incorrect Options:** * **A. Arginine Vasopressin (AVP):** This is the naturally occurring ADH. It acts on both V1 (causing vasoconstriction) and V2 receptors. It has a very short half-life (10–20 minutes), making it impractical for the long-term management of CDI. * **C. Lypressin:** A synthetic analogue (8-lysine vasopressin) formerly used for CDI. However, it is less potent and has a shorter duration of action than Desmopressin, making it obsolete. * **D. Terlipressin:** A prodrug of lysine vasopressin with high **V1 selectivity**. It is primarily used for managing esophageal variceal bleeding and Hepatorenal Syndrome, not for its antidiuretic effects. **High-Yield Clinical Pearls for NEET-PG:** * **Routes of Desmopressin:** Available as nasal spray (most common), oral tablets, and parenteral injections. * **Other Uses of Desmopressin:** Nocturnal enuresis, Hemophilia A, and von Willebrand Disease (Type 1) because it releases Factor VIII and vWF from endothelial storage (Weibel-Palade bodies). * **Side Effect:** The most serious adverse effect is **water intoxication** leading to hyponatremia. * **Diagnostic Tip:** Desmopressin is used in the **Water Deprivation Test** to differentiate Central DI (responds to dDAVP) from Nephrogenic DI (no response).

Q: Which of the following contains emergency contraception?

Levonorgestrel. **Levonorgestrel (LNG)** is the gold standard for hormonal emergency contraception [1]. It is a second-generation synthetic progestin. When used as emergency contraception (the "morning-after pill"), it is typically administered as a single **1.5 mg dose** within 72 hours of unprotected intercourse [1]. Its primary mechanism of action is the **delay or inhibition of ovulation** by suppressing the LH surge. It is not an abortifacient and is ineffective once implantation has occurred. **Analysis of Incorrect Options:** * **Cyproterone:** An anti-androgenic progestin used primarily in the treatment of severe acne, hirsutism (PCOS), and as part of combined oral contraceptives (e.g., Diane-35) [2]. * **Desogestrel:** A third-generation progestin commonly used in "mini-pills" (Progestogen-only pills) for daily contraception [2]. It is not used in the high doses required for emergency intervention. * **Medroxyprogesterone (MPA):** Primarily used as an injectable contraceptive (**DMPA/Antara**) given every 3 months (150 mg IM). It provides long-term depot contraception rather than emergency post-coital prevention. **High-Yield Clinical Pearls for NEET-PG:** * **Yuzpe Regimen:** An older method using high doses of combined OCPs (Ethinylestradiol + Levonorgestrel); it is less effective and causes more nausea than LNG alone. * **Ulipristal Acetate:** A selective progesterone receptor modulator (SPRM) that is now considered more effective than LNG, especially between 72–120 hours [1]. * **Copper T (IUCD):** The **most effective** method of emergency contraception if inserted within 5 days of unprotected intercourse. * **Mifepristone:** Can also be used as emergency contraception at low doses (10–25 mg).

Q: Which of the following is NOT an established use of estrogen?

Treatment of breast cancer. **Explanation:** The correct answer is **C (Treatment of breast cancer)**. Estrogens are generally contraindicated in breast cancer because most breast tumors are **estrogen-receptor (ER) positive** [3]. Estrogen acts as a growth factor for these malignant cells, promoting tumor progression [2]. Instead, the management of breast cancer typically involves **anti-estrogens** (like Tamoxifen) or **Aromatase Inhibitors** (like Letrozole) to block estrogenic effects [3]. **Analysis of other options:** * **A. Senile Vaginitis:** Post-menopausal estrogen deficiency leads to thinning of the vaginal epithelium (atrophic vaginitis). Topical or systemic estrogen restores the mucosal integrity and is a standard treatment. * **B. Carcinoma of the Prostate:** While not the first-line treatment today (due to the availability of GnRH analogs), high-dose estrogen (e.g., Diethylstilbestrol) was historically used to suppress LH secretion via negative feedback, thereby reducing testosterone levels which drive prostate cancer. * **D. Delayed Puberty:** In girls with primary hypogonadism (e.g., Turner Syndrome), estrogen is used to induce the development of secondary sexual characteristics and ensure proper bone maturation. **NEET-PG High-Yield Pearls:** * **Drug of Choice:** Estrogen is the most effective treatment for **postmenopausal vasomotor symptoms** (hot flashes) [4]. * **Risk Factor:** Unopposed estrogen therapy increases the risk of **endometrial carcinoma**; therefore, progestins are always added in women with an intact uterus [1]. * **Side Effect:** Estrogens increase the risk of **thromboembolism** by increasing the synthesis of clotting factors (II, VII, IX, X) and decreasing Antithrombin III. * **Exception:** While estrogen generally promotes breast cancer, very high-dose estrogen was paradoxically used in the past for postmenopausal breast cancer, but it is **not** an established or standard use in modern practice.

Q: All of the following are anti-androgens except:

Dihydrotestosterone. **Explanation:** The correct answer is **Dihydrotestosterone (DHT)**. To answer this question, one must distinguish between an androgen (agonist) and an anti-androgen (antagonist or synthesis inhibitor). **Why Dihydrotestosterone is the correct answer:** Dihydrotestosterone is a potent, naturally occurring **androgen** (agonist). It is the active metabolite of testosterone, converted by the enzyme 5-alpha reductase. DHT has a higher affinity for androgen receptors than testosterone and is responsible for the development of male external genitalia, prostate growth, and male-pattern baldness. Since it promotes androgenic effects, it is not an anti-androgen. **Why the other options are incorrect:** * **Finasteride:** It is a **5-alpha reductase inhibitor**. By preventing the conversion of testosterone to DHT, it acts as an anti-androgen. It is primarily used for Benign Prostatic Hyperplasia (BPH) and androgenic alopecia. * **Flutamide:** It is a **pure androgen receptor antagonist**. It competes with DHT for binding sites on the target cell. It is frequently used in the management of metastatic prostatic carcinoma. * **Cyproterone acetate:** It is a **steroidal androgen receptor antagonist** that also possesses progestational activity. It inhibits the feedback loop by suppressing LH secretion and is used for treating hirsutism in females and precocious puberty. **High-Yield Clinical Pearls for NEET-PG:** * **Spironolactone:** A potassium-sparing diuretic that also acts as an androgen receptor antagonist (used in PCOS). * **Abiraterone:** A CYP17 inhibitor used in castration-resistant prostate cancer to block all androgen synthesis. * **Bicalutamide:** Preferred over Flutamide for prostate cancer due to less hepatotoxicity and once-daily dosing. * **Teratogenicity:** 5-alpha reductase inhibitors (Finasteride/Dutasteride) are contraindicated in pregnancy as they can cause feminization of a male fetus.

Q: What is a common cause of gynecomastia and infertility in men?

Cimetidine. **Explanation:** **Cimetidine**, a first-generation H2-receptor antagonist, is a classic cause of gynecomastia and infertility in men due to its unique endocrine side-effect profile. It acts through two primary mechanisms: 1. **Anti-androgenic effects:** It binds to androgen receptors and inhibits the action of dihydrotestosterone (DHT). 2. **Hyperprolactinemia:** It inhibits the metabolism of estradiol and can increase prolactin levels, especially when administered intravenously. These effects lead to an altered estrogen-to-androgen ratio, resulting in breast tissue enlargement (gynecomastia) and reduced sperm count (oligospermia/infertility). **Analysis of Incorrect Options:** * **A. Digitalis:** While chronic Digoxin use is associated with gynecomastia (due to its steroid-like structure which can mimic estrogen), it is not a primary or common cause of infertility compared to the potent anti-androgenic action of Cimetidine. * **B. Omeprazole:** As a Proton Pump Inhibitor (PPI), it is generally devoid of significant anti-androgenic or pro-estrogenic effects. * **C. Erythromycin:** This is a macrolide antibiotic. Its primary side effects are GI upset and QT prolongation; it does not affect the endocrine system or fertility. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Gynecomastia (DISCO):** **D**igoxin, **I**soniazid, **S**pironolactone, **C**imetidine, **O**estrogens. * **Cimetidine & P450:** It is a potent **enzyme inhibitor**, leading to increased levels of drugs like Warfarin, Theophylline, and Phenytoin. * **Modern H2 Blockers:** Newer agents like Ranitidine, Famotidine, and Nizatidine do **not** cause these endocrine side effects.

Question 1

Which one of the following is true of adrenal suppression due to steroid therapy?

Accepted Answer

It should be expected in anyone receiving greater than 5 mg of prednisolone daily

Answer

It is not associated with atrophy of the adrenal glands

Answer

It does not occur in patients receiving inhaled steroids

Answer

Following cessation, the stress response normalizes after 8 weeks

Question 2

Cinacalcet acts by which of the following mechanisms?

Accepted Answer

Decreasing parathyroid hormone secretion

Answer

Inhibiting RANK-ligand

Answer

Activating osteoblasts

Answer

Increasing vitamin D levels

Question 3

Steroids are indicated in all of the following conditions except?

Accepted Answer

Oral ulcers in AIDS patients

Answer

Edema following extractions

Answer

TMJ arthritis

Answer

Angioneurotic edema

Question 4

All of the following are true regarding adverse effects of chlorpropamide except?

Accepted Answer

Less incidence of hypoglycemia

Answer

Releases ADH

Answer

More incidence of weight gain

Answer

Disulfiram like reaction may occur

Question 5

A 54-year-old obese patient with type 2 diabetes mellitus and a history of alcoholism should probably not receive metformin because it can increase the risk of:

Accepted Answer

Lactic acidosis

Answer

Disulfiram-like reaction

Answer

Hypoglycemia

Answer

Severe hepatic toxicity

Question 6

Which selective V2 receptor agonist is useful for the treatment of central diabetes insipidus?

Accepted Answer

Desmopressin

Answer

Arginine vasopressin

Answer

Lypressin

Answer

Terlipressin

Question 7

Which of the following contains emergency contraception?

Accepted Answer

Levonorgestrel

Answer

Cyproterone

Answer

Desogestrel

Answer

Medroxyprogesterone

Question 8

Which of the following is NOT an established use of estrogen?

Accepted Answer

Treatment of breast cancer

Answer

Treatment of senile vaginitis

Answer

Treatment of carcinoma of the prostate

Answer

Management of delayed puberty

Question 9

All of the following are anti-androgens except:

Accepted Answer

Dihydrotestosterone

Answer

Finasteride

Answer

Flutamide

Answer

Cyproterone acetate

Question 10

What is a common cause of gynecomastia and infertility in men?

Accepted Answer

Cimetidine

Answer

Digitalis

Answer

Omeprazole

Answer

Erythromycin

Endocrine Pharmacology — MCQs

Endocrine Pharmacology — MCQs

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