Endocrine Pharmacology Practice Questions

Q: What is the mechanism of action of bromocriptine?

Agonism at D2 receptors. **Bromocriptine** is a semi-synthetic ergot alkaloid that acts as a potent **selective agonist at Dopamine D2 receptors** [1]. In the anterior pituitary, dopamine acts as the primary prolactin-inhibiting hormone. By stimulating D2 receptors on lactotrophs, bromocriptine inhibits the synthesis and release of prolactin. It also acts on D2 receptors in the nigrostriatal pathway, which accounts for its utility in movement disorders. **Analysis of Options:** * **Option A (Correct):** Bromocriptine mimics the action of endogenous dopamine at D2 receptors, making it the drug of choice for hyperprolactinemia. * **Option B & C:** Antagonism at D2 or D1 receptors is the mechanism of **Antipsychotics** (e.g., Haloperidol). D2 antagonism actually *causes* hyperprolactinemia as a side effect. * **Option D:** While some ergot derivatives have complex effects on alpha receptors, bromocriptine’s primary therapeutic effects in endocrine and neurological conditions are mediated via D2 agonism. **Clinical Pearls for NEET-PG:** 1. **Indications:** Hyperprolactinemia (Prolactinoma), Acromegaly (at high doses), Parkinson’s disease, and Type 2 Diabetes Mellitus (Quick-release formulation). 2. **Drug of Choice:** While bromocriptine is classic, **Cabergoline** is now preferred for prolactinomas due to its higher efficacy, longer half-life (twice-weekly dosing), and better tolerability. 3. **Side Effects:** Nausea/vomiting (due to CTZ stimulation), postural hypotension, and digital vasospasm. 4. **Contraindication:** History of psychiatric disorders (may exacerbate psychosis) and valvular heart disease (ergot-related fibrosis).

Q: Which of the following drugs is administered intranasally?

Desmopressin. **Explanation:** **Desmopressin (Correct Answer):** Desmopressin is a synthetic analogue of Vasopressin (ADH). It is commonly administered **intranasally** because it is a peptide drug that would otherwise be degraded by gastric enzymes if taken orally (though oral formulations exist with higher doses). The nasal route provides rapid absorption through the vascularized nasal mucosa, bypassing first-pass metabolism. It is the preferred route for treating **Central Diabetes Insipidus** and nocturnal enuresis. **Analysis of Incorrect Options:** * **Ribavirin:** This antiviral is primarily administered **orally** or via **aerosol inhalation** (using a small particle aerosol generator) specifically for treating Respiratory Syncytial Virus (RSV) in infants. * **Amiloride:** A potassium-sparing diuretic used in hypertension and heart failure, it is administered **orally**. (Note: While experimental inhaled versions exist for Cystic Fibrosis, it is not the standard clinical route). * **Oseltamivir:** This neuraminidase inhibitor used for Influenza is a prodrug administered **orally**. In contrast, Zanamivir (another neuraminidase inhibitor) is administered via inhalation. **High-Yield Clinical Pearls for NEET-PG:** * **Desmopressin (DDAVP)** acts on **V2 receptors** with minimal V1 (vasoconstrictor) activity, making it safer for patients with cardiovascular issues compared to natural ADH. * **Other drugs given intranasally:** Calcitonin (for osteoporosis), GnRH agonists (Buserelin), Midazolam (for acute seizures), and Sumatriptan (for migraines). * **Therapeutic uses of Desmopressin:** Central Diabetes Insipidus, Type 1 Von Willebrand Disease, and Hemophilia A (it increases Factor VIII and vWF levels).

Q: Low dose progestational contraceptives primarily act on which of the following?

Cervix. **Explanation:** The primary mechanism of action for **low-dose progestational contraceptives** (such as Progestogen-Only Pills or POPs) is the alteration of **cervical mucus**. 1. **Why Option C is Correct:** Low doses of progesterone make the cervical mucus thick, viscous, and scanty. This creates a "hostile" environment that acts as a physical barrier, preventing sperm penetration into the upper reproductive tract. This is the most consistent and immediate effect of low-dose formulations. 2. **Why Other Options are Incorrect:** * **Option D (Pituitary):** While high-dose progesterone (like DMPA) or Combined Oral Contraceptives (COCs) reliably suppress the hypothalamic-pituitary-ovarian axis to inhibit ovulation, low-dose POPs do **not** consistently suppress ovulation (ovulation occurs in about 60% of cycles). * **Option B (Uterine Endometrium):** Progesterone does cause endometrial atrophy (making it out of sync for implantation), but this is considered a secondary/backup mechanism rather than the primary one for low-dose formulations. * **Option A (Oviductal Motility):** Progesterone can decrease the motility and ciliary activity of the fallopian tubes, but this is a minor contributory factor compared to the cervical effect. **High-Yield Clinical Pearls for NEET-PG:** * **POPs (Minipill):** Must be taken at the same time every day (3-hour window). If a dose is missed by >3 hours, backup contraception is needed for 48 hours. * **Drug of Choice:** POPs are the contraceptive of choice for **lactating mothers** as they do not suppress milk production (unlike estrogens). * **Primary MOA Summary:** * **COCs:** Inhibition of Ovulation (Primary). * **POPs:** Cervical mucus thickening (Primary). * **IUCD (Cu-T):** Sterile inflammatory response/Spermicidal (Primary). * **LNG-IUS (Mirena):** Endometrial atrophy (Primary).

Q: Which SERM drug is used in the treatment of osteoporosis?

Raloxifene. ### Explanation **Correct Answer: A. Raloxifene** **Mechanism and Rationale:** Raloxifene is a **Selective Estrogen Receptor Modulator (SERM)**. Its clinical utility stems from its tissue-specific action: it acts as an **estrogen agonist in bone**, where it inhibits osteoclast activity and decreases bone resorption, thereby increasing bone mineral density. Crucially, it acts as an **estrogen antagonist in the breast and uterus**, which reduces the risk of estrogen-dependent cancers (unlike older HRT or Tamoxifen). It is specifically FDA-approved for the prevention and treatment of postmenopausal osteoporosis. **Analysis of Incorrect Options:** * **B. Estrogen:** While estrogen prevents bone loss, it is **not a SERM**. It is a hormone used in Hormone Replacement Therapy (HRT). Due to risks of breast cancer and thromboembolism, it is no longer the first-line treatment for osteoporosis. * **C. Strontium (Strontium Ranelate):** This is a divalent cation that both increases bone formation and decreases resorption. However, it is **not a SERM** and is rarely used now due to cardiovascular safety concerns. * **D. Alendronate:** This is a **Bisphosphonate**, which is the first-line drug class for osteoporosis. While highly effective, it belongs to a different pharmacological class than SERMs. **High-Yield Clinical Pearls for NEET-PG:** * **SERM Profile of Raloxifene:** Agonist on Bone and Lipid metabolism; Antagonist on Breast and Endometrium (No risk of endometrial cancer, unlike Tamoxifen). * **Side Effects:** Most common are hot flashes and leg cramps. The most serious risk is **Venous Thromboembolism (VTE)**. * **Drug of Choice:** While Bisphosphonates (e.g., Alendronate) are the overall DOC for osteoporosis, Raloxifene is preferred in postmenopausal women who also have a high risk of breast cancer.

Q: Vasopressin is inhibited by which of the following substances?

Alcohol. **Explanation:** **Vasopressin (Antidiuretic Hormone/ADH)** is synthesized in the hypothalamus and released from the posterior pituitary. Its primary role is to maintain water homeostasis by promoting water reabsorption in the renal collecting ducts via V2 receptors. **1. Why Alcohol is Correct:** Alcohol (Ethanol) is a potent **inhibitor of ADH release** from the neurohypophysis. By suppressing ADH, alcohol prevents the kidneys from reabsorbing water, leading to the production of large volumes of dilute urine (diuresis). This mechanism is a primary contributor to the dehydration and "hangover" symptoms associated with alcohol consumption. **2. Why the Other Options are Incorrect:** Unlike alcohol, the other three options are known to **stimulate** ADH release or **potentiate** its action, making them useful in the treatment of partial Central Diabetes Insipidus: * **Carbamazepine:** An anticonvulsant that increases the sensitivity of renal tubules to ADH and stimulates its release. * **Chlorpropamide:** A first-generation sulfonylurea that enhances the action of ADH on V2 receptors in the kidney. * **Clofibrate:** A lipid-lowering agent that stimulates the central release of ADH from the posterior pituitary. **Clinical Pearls for NEET-PG:** * **SIADH:** Carbamazepine and Chlorpropamide are common causes of drug-induced SIADH (Syndrome of Inappropriate ADH secretion), leading to hyponatremia. * **Other Inhibitors:** In addition to alcohol, **Phenytoin** and **Lithium** (which causes nephrogenic DI) also inhibit ADH action/release. * **Vaptans:** Tolvaptan and Conivaptan are specific ADH receptor antagonists used to treat euvolemic hyponatremia.

Q: A postmenopausal woman with a family history of osteoporosis completes a bone mineral density work-up and her T-score is -2.6. She tried a course of teriparatide a year ago but complained of depression and mood changes. You decided to try an antibody-based therapy and schedule a time for an injection. What is the drug you have selected?

Denosumab. **Explanation:** The patient has a T-score of -2.6, which confirms a diagnosis of **osteoporosis** (T-score ≤ -2.5). Given her history of mood changes with teriparatide and the requirement for an **antibody-based therapy** administered via injection, **Denosumab** is the correct choice. **Why Denosumab is correct:** Denosumab is a fully human monoclonal antibody that targets and binds to **RANKL** (Receptor Activator of Nuclear Factor kappa-B Ligand). By inhibiting RANKL, it prevents the maturation and activation of osteoclasts, thereby decreasing bone resorption and increasing bone mineral density. It is administered subcutaneously every 6 months. **Why other options are incorrect:** * **Calcitonin:** While used for osteoporosis, it is a peptide hormone (not an antibody) usually administered via nasal spray or injection. It is less efficacious than Denosumab. * **Dihydrotachysterol:** This is a synthetic analogue of Vitamin D. It is not an antibody and is primarily used in hypoparathyroidism. * **Infliximab:** This is a monoclonal antibody, but it targets **TNF-alpha**. It is used for inflammatory conditions like Rheumatoid Arthritis or Crohn’s disease, not for treating osteoporosis. **NEET-PG High-Yield Pearls:** * **Mechanism:** Denosumab mimics the natural action of **Osteoprotegerin (OPG)**. * **Teriparatide:** A recombinant PTH (1-34) analogue. It is anabolic (builds bone) but carries a black box warning for Osteosarcoma (avoid in Paget’s disease). * **Bisphosphonates:** First-line for osteoporosis; they inhibit farnesyl pyrophosphate synthase. * **Side Effect:** Like bisphosphonates, Denosumab is associated with a risk of **Osteonecrosis of the Jaw (ONJ)** and atypical femur fractures.

Q: Which of the following is used in the treatment of hyperprolactinemia?

Bromocriptine. Explanation: Correct Option: C. Bromocriptine Hyperprolactinemia is primarily managed by enhancing dopaminergic tone. Prolactin secretion from the anterior pituitary is under tonic inhibition by Dopamine (acting on D2 receptors). Bromocriptine is a potent D2 receptor agonist and an ergot derivative [1]. By stimulating these receptors, it effectively inhibits the synthesis and release of prolactin, thereby restoring ovulatory function and shrinking prolactin-secreting adenomas (prolactinomas) [2]. Analysis of Incorrect Options: A. Cimetidine: This is an H2-receptor antagonist used for peptic ulcers. Interestingly, cimetidine is known to cause hyperprolactinemia and gynecomastia as a side effect because it has anti-androgenic properties and can increase prolactin levels. B. Methysergide: An ergot alkaloid that acts as a 5-HT2 receptor antagonist. It was historically used for migraine prophylaxis but is not used for prolactin regulation. C. Ondansetron: A 5-HT3 receptor antagonist used primarily as an anti-emetic in chemotherapy-induced nausea and vomiting. It has no significant effect on prolactin levels. High-Yield Clinical Pearls for NEET-PG: * Cabergoline is currently the drug of choice for hyperprolactinemia because it is more effective, has a longer half-life (twice-weekly dosing), and better tolerability compared to Bromocriptine [1]. * Bromocriptine remains the preferred drug if pregnancy is desired, due to a longer track record of safety data. * Side Effects: Common side effects of dopamine agonists include nausea, dizziness (orthostatic hypotension), and nasal congestion. * Other uses of Bromocriptine: Type 2 Diabetes Mellitus (quick-release formulation) and Parkinson’s Disease.

Q: What is the special feature of glargine insulin?

It produces a smooth peakless effect.. **Explanation:** **Insulin Glargine** is a long-acting recombinant DNA analog of human insulin. Its unique pharmacological profile is dictated by its chemical structure: two arginine residues are added to the C-terminus of the B-chain, and asparagine is replaced by glycine at position A21. 1. **Why Option A is Correct:** Glargine is formulated at an acidic pH (4.0), where it is completely soluble. However, when injected subcutaneously, the neutral physiological pH causes it to **precipitate into micro-crystals**. These crystals dissolve slowly and release insulin into the bloodstream at a constant, steady rate. This results in a **"peakless" concentration profile** that mimics basal insulin secretion for approximately 24 hours, significantly reducing the risk of nocturnal hypoglycemia. 2. **Why Other Options are Incorrect:** * **Option B:** Due to its long duration of action (20–24 hours), it is specifically designed for **once-daily administration** to provide basal coverage. * **Option C:** Glargine is **insoluble at pH 7**. Its precipitation at physiological pH is the very mechanism that allows for its slow absorption. * **Option D:** Because it lacks a peak and has a slow onset, it **cannot control postprandial (mealtime) hyperglycemia**. Rapid-acting analogs (Lispro, Aspart, Glulisine) are required for this purpose. **High-Yield NEET-PG Pearls:** * **Mixing:** Glargine should **not be mixed** with other insulins in the same syringe, as its acidic pH can cause the other insulin to precipitate, altering its absorption. * **Safety:** It has the lowest risk of nocturnal hypoglycemia among conventional long-acting insulins. * **Other Basal Insulins:** **Detemir** (binds to albumin via a fatty acid chain) and **Degludec** (forms multi-hexamers; longest half-life >40 hours).

Question 1

What is the mechanism of action of bromocriptine?

Accepted Answer

Agonism at D2 receptors

Answer

Antagonism at D2 receptors

Answer

Antagonism at D1 receptors

Answer

Antagonism at alpha receptors

Question 2

Monocomponent insulin has all the following advantages except?

Accepted Answer

Longer duration of action

Answer

Can be used in pregnancy

Answer

Less hypoglycemic episodes

Answer

Less chances of lipodystrophy

Question 3

Which of the following drugs is administered intranasally?

Accepted Answer

Desmopressin

Answer

Ribavarin

Answer

Amiloride

Answer

Oseltamivir

Question 4

Low dose progestational contraceptives primarily act on which of the following?

Accepted Answer

Cervix

Answer

Oviductal motility

Answer

Uterine endometrium

Answer

Pituitary

Question 5

Which SERM drug is used in the treatment of osteoporosis?

Accepted Answer

Raloxifene

Answer

Estrogen

Answer

Strontium

Answer

Alendroate

Question 6

Vasopressin is inhibited by which of the following substances?

Accepted Answer

Alcohol

Answer

Carbamazepine

Answer

Clofibrate

Answer

Chlorpropamide

Question 7

A postmenopausal woman with a family history of osteoporosis completes a bone mineral density work-up and her T-score is -2.6. She tried a course of teriparatide a year ago but complained of depression and mood changes. You decided to try an antibody-based therapy and schedule a time for an injection. What is the drug you have selected?

Accepted Answer

Denosumab

Answer

Calcitonin

Answer

Dihydrotachysterol

Answer

Infliximab

Question 8

Which of the following is used in the treatment of hyperprolactinemia?

Accepted Answer

Bromocriptine

Answer

Cimetidine

Answer

Methysergide

Answer

Ondansetron

Question 9

Which of the following statements regarding finasteride is FALSE?

Accepted Answer

It blocks the conversion of dihydrotestosterone to testosterone.

Answer

It is used in the medical treatment of benign prostatic hypertrophy (BPH).

Answer

Impotence is well documented after its use.

Answer

It is a 5-alpha reductase inhibitor.

Question 10

What is the special feature of glargine insulin?

Accepted Answer

It produces a smooth peakless effect.

Answer

It is not suitable for once daily administration.

Answer

It remains soluble at pH 7.

Answer

It can control mealtime hyperglycemia.

Endocrine Pharmacology — MCQs

Endocrine Pharmacology — MCQs

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