Endocrine Pharmacology — MCQs

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?

Q17Easy

Prolactin secretion is inhibited by:

Q18Easy

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

Q19Easy

What is the special feature of glargine insulin?

Q20Easy

Bromocriptine can be used in the following conditions, except:

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 11: Monocomponent insulin has all the following advantages except?

A. Can be used in pregnancy
B. Less hypoglycemic episodes
C. Longer duration of action (Correct Answer)
D. Less chances of lipodystrophy

Explanation: **Explanation:** **Monocomponent Insulin (MC Insulin)** is a highly purified form of insulin obtained by gel filtration and ion-exchange chromatography. It contains less than 10 ppm (parts per million) of proinsulin and other impurities, compared to conventional insulin (which contains ~10,000 ppm) or Single Peak Insulin (~300 ppm). **Why Option C is the correct answer:** The purification process of insulin affects its **immunogenicity**, not its pharmacokinetics. The duration of action of insulin is determined by its formulation (e.g., Regular vs. NPH vs. Glargine) and the physical state (crystalline vs. amorphous), not by the level of purity [1]. Therefore, monocomponent insulin does not inherently have a longer duration of action than conventional insulin of the same type. **Analysis of incorrect options:** * **Option A (Pregnancy):** Highly purified insulins are preferred in pregnancy to minimize the risk of transplacental transfer of insulin antibodies, which could potentially affect fetal glucose metabolism. * **Option B (Less hypoglycemia):** While the primary benefit is reduced immunogenicity, the formation of insulin antibodies (seen with impure insulin) can sometimes lead to unpredictable release of insulin from antibody complexes, causing delayed hypoglycemia. MC insulin reduces this risk. * **Option D (Less lipodystrophy):** Local site reactions like lipoatrophy and insulin resistance are primarily mediated by immune responses to impurities (proinsulin, glucagon, somatostatin) [2]. By removing these, MC insulin significantly reduces the incidence of lipodystrophy. **High-Yield Facts for NEET-PG:** * **Purity Levels:** Conventional (>10,000 ppm) → Single Peak (~300 ppm) → Monocomponent (<10 ppm). * **Indications for MC Insulin:** Insulin resistance (due to antibodies), local allergy, lipoatrophy at the injection site, and pregnancy. * **Source:** Most MC insulins are porcine (pig) because porcine insulin differs from human insulin by only one amino acid, making it less immunogenic than bovine insulin.

Question 12: All of the following drugs reduce the efficacy of combined oral contraceptive pills when used together, EXCEPT:

A. Rifampin
B. Penicillin (Correct Answer)
C. Griseofulvin
D. Carbamazepine

Explanation: The efficacy of **Combined Oral Contraceptive Pills (COCPs)** is primarily dependent on maintaining therapeutic serum levels of estrogen and progestin. Drugs that induce hepatic enzymes or interfere with enterohepatic circulation can lower these levels, leading to contraceptive failure. ### **Explanation of the Correct Answer** **B. Penicillin:** Historically, it was believed that broad-spectrum antibiotics (like Penicillin or Tetracycline) reduced COCP efficacy by altering gut flora and interrupting the **enterohepatic circulation** of estrogens. However, current clinical evidence and pharmacokinetic studies have shown that plasma concentrations of contraceptive steroids are **not** significantly lowered by non-enzyme-inducing antibiotics. Therefore, Penicillin does not clinically reduce the efficacy of COCPs. ### **Explanation of Incorrect Options** The other options are all potent **Microsomal Enzyme Inducers** (specifically inducing CYP3A4), which accelerate the metabolism of estrogen and progestin, leading to sub-therapeutic levels and "breakthrough" ovulation: * **A. Rifampin:** The most potent inducer; it significantly increases the clearance of COCPs. * **C. Griseofulvin:** An antifungal known to induce hepatic enzymes and cause contraceptive failure. * **D. Carbamazepine:** An anticonvulsant that induces the cytochrome P450 system, reducing the half-life of steroid hormones. ### **High-Yield NEET-PG Pearls** * **The "Rifampin Exception":** Rifampin is the **only** antibiotic proven to necessitate additional contraceptive precautions (back-up methods). * **Other Inducers to Watch:** Phenytoin, Phenobarbitone, and St. John’s Wort also reduce COCP efficacy. * **Management:** For patients on long-term enzyme-inducing drugs, the recommended contraceptive choice is usually an **IUD** or a high-dose (50μg) estrogen pill (though IUD is preferred). * **Anticonvulsant Exception:** **Sodium Valproate** and **Levetiracetam** are enzyme inhibitors/neutral and do *not* typically interfere with COCPs.

Question 13: Which SERM drug is used in the treatment of osteoporosis?

A. Raloxifene (Correct Answer)
B. Estrogen
C. Strontium
D. Alendroate

Explanation: ### 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.

Question 14: Vasopressin is inhibited by which of the following substances?

A. Alcohol (Correct Answer)
B. Carbamazepine
C. Clofibrate
D. Chlorpropamide

Explanation: **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.

Question 15: Which of the following insulin preparations has a slow onset of action?

A. Glargine (Correct Answer)
B. Lispro
C. Regular
D. NPH

Explanation: ### Explanation Insulin preparations are classified based on their onset and duration of action. To answer this question, one must distinguish between rapid-acting, short-acting, intermediate-acting, and long-acting insulins. **Correct Option: A. Glargine** Insulin Glargine is a **long-acting basal insulin**. It is formulated at an acidic pH (4.0), which causes it to precipitate into micro-crystals upon subcutaneous injection. These crystals dissolve slowly into the bloodstream, resulting in a **slow onset of action** (typically 1–2 hours) and a prolonged, "peakless" duration of action (up to 24 hours). This makes it ideal for maintaining basal insulin levels. **Incorrect Options:** * **B. Lispro:** This is an **ultra-rapid-acting** insulin analog. It has a very fast onset (5–15 minutes) because it does not form hexamers, allowing for immediate absorption. It is used for postprandial glucose control. * **C. Regular:** This is **short-acting** insulin. It has a relatively fast onset (30–60 minutes) compared to long-acting versions and is the only form that can be given intravenously in emergencies like DKA. * **D. NPH (Neutral Protamine Hagedorn):** This is an **intermediate-acting** insulin. While slower than Regular insulin, its onset (1–2 hours) is similar to Glargine, but it has a distinct peak (4–10 hours) and a shorter duration, making it less "slow and steady" than Glargine. **High-Yield Clinical Pearls for NEET-PG:** * **Peakless Insulins:** Glargine and Degludec are considered "peakless," significantly reducing the risk of nocturnal hypoglycemia. * **Longest Acting:** **Degludec** has the longest half-life (>40 hours). * **Fastest Acting:** **Aspart, Lispro, and Glulisine** (Mnemonic: "No **L**ag" – **L**ispro, **A**spart, **G**lulisine). * **Inhaled Insulin:** Afrezza is a rapid-acting inhaled insulin but is contraindicated in smokers and COPD patients.

Question 16: 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?

A. Calcitonin
B. Dihydrotachysterol
C. Infliximab
D. Denosumab (Correct Answer)

Explanation: **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.

Question 17: Prolactin secretion is inhibited by:

A. Dopamine antagonist
B. GABA
C. Neurophysin
D. Bromocriptine (Correct Answer)

Explanation: **Explanation:** Prolactin secretion is unique among anterior pituitary hormones because it is under **tonic inhibitory control** by the hypothalamus. The primary Prolactin Inhibiting Factor (PIF) is **Dopamine**, which acts on **D2 receptors** located on lactotrophs. **Why Bromocriptine is Correct:** Bromocriptine is a potent **D2 receptor agonist** (ergot derivative). By mimicking the action of endogenous dopamine, it directly inhibits the synthesis and release of prolactin. It is a first-line treatment for hyperprolactinemia and prolactinomas. **Analysis of Incorrect Options:** * **A. Dopamine Antagonists:** These drugs (e.g., Metoclopramide, Haloperidol, Risperidone) block D2 receptors, removing the "brake" on prolactin secretion. This leads to **hyperprolactinemia**, causing side effects like galactorrhea and gynecomastia. * **B. GABA:** While GABA can have minor inhibitory effects on various pituitary hormones, it is not the primary physiological regulator of prolactin. * **C. Neurophysin:** These are carrier proteins for Oxytocin and Vasopressin (ADH) produced in the hypothalamus and transported to the posterior pituitary. They have no role in inhibiting prolactin. **High-Yield Clinical Pearls for NEET-PG:** * **Cabergoline** is now preferred over Bromocriptine due to its longer half-life (dosed twice weekly) and better tolerability (fewer GI side effects). * **TRH (Thyrotropin-Releasing Hormone)** acts as a prolactin-releasing factor. Therefore, **Primary Hypothyroidism** (high TRH) can lead to secondary hyperprolactinemia. * **Hook Effect:** In cases of extremely high prolactin, lab assays may show falsely low levels; serial dilution is required for accurate diagnosis.

Question 18: Which of the following is used in the treatment of hyperprolactinemia?

A. Cimetidine
B. Methysergide
C. Bromocriptine (Correct Answer)
D. Ondansetron

Explanation: 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.

Question 19: What is the special feature of glargine insulin?

A. It produces a smooth peakless effect. (Correct Answer)
B. It is not suitable for once daily administration.
C. It remains soluble at pH 7.
D. It can control mealtime hyperglycemia.

Explanation: **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 20: Bromocriptine can be used in the following conditions, except:

A. Hyperprolactinoma
B. Acromegaly
C. Parkinsonism
D. Diabetes insipidus (Correct Answer)

Explanation: **Explanation:** Bromocriptine is a **semisynthetic ergot alkaloid** that acts as a potent **D2 receptor agonist**. Its clinical utility is derived from its ability to mimic dopamine in various pathways. **Why Diabetes Insipidus is the Correct Answer:** Diabetes insipidus (DI) is characterized by a deficiency of Antidiuretic Hormone (ADH) or resistance to it. Bromocriptine has no effect on ADH secretion or the V2 receptors in the kidney. In fact, Bromocriptine is used to treat **Diabetes Mellitus Type 2** (specifically a quick-release formulation approved by the FDA), but it plays no role in the management of Diabetes Insipidus. **Analysis of Other Options:** * **Hyperprolactinoma:** Dopamine is the natural "Prolactin Inhibiting Hormone." By stimulating D2 receptors on pituitary lactotrophs, Bromocriptine effectively suppresses prolactin secretion and shrinks prolactin-secreting tumors. * **Acromegaly:** While dopamine stimulates Growth Hormone (GH) in healthy individuals, it paradoxically **suppresses GH secretion** in patients with acromegaly. Thus, Bromocriptine is used as an adjuvant treatment. * **Parkinsonism:** Parkinson’s disease involves a deficiency of dopamine in the nigrostriatal pathway. As a direct D2 agonist, Bromocriptine helps restore dopaminergic activity and improve motor symptoms. **High-Yield Clinical Pearls for NEET-PG:** 1. **Drug of Choice:** While Bromocriptine is effective, **Cabergoline** is now the preferred drug for hyperprolactinemia due to its higher efficacy, longer half-life (twice-weekly dosing), and better side-effect profile. 2. **Specific Side Effect:** Bromocriptine can cause **digital vasospasm** (Raynaud’s-like phenomenon) and pulmonary/retroperitoneal fibrosis with long-term use. 3. **Postpartum:** It was previously used to suppress postpartum lactation but is now avoided due to risks of seizures and stroke.

Practice by Chapter

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