Endocrine Pharmacology Practice Questions

Q: What is the drug of choice for central diabetes insipidus?

Desmopressin. **Explanation:** **Desmopressin (dDAVP)** is the drug of choice for **Central Diabetes Insipidus (CDI)**. CDI is characterized by a deficiency of Antidiuretic Hormone (ADH) from the posterior pituitary. Desmopressin is a synthetic analogue of vasopressin with two key modifications: it has a longer half-life and is a **selective V2 receptor agonist**. By acting on V2 receptors in the renal collecting ducts, it increases water reabsorption without causing the significant vasoconstriction associated with V1 receptor activation. It can be administered intranasally, orally, or parenterally. **Analysis of Incorrect Options:** * **Vasopressin (ADH):** While it is the endogenous hormone, it is not the drug of choice because it acts non-selectively on both V1 (vasoconstriction) and V2 receptors. It has a very short duration of action (15–20 minutes), requiring frequent dosing, and carries a risk of hypertension and myocardial ischemia. * **Lypressin:** This is a synthetic analogue (8-lysine vasopressin) formerly used for CDI. However, it has a shorter duration of action and less potency compared to Desmopressin, making it obsolete in modern practice. * **Presselin:** This is not a standard pharmacological agent used in the treatment of Diabetes Insipidus. **High-Yield Clinical Pearls for NEET-PG:** * **V2 Selectivity:** Desmopressin has a V2:V1 selectivity ratio of approximately 2000:1. * **Other Uses of Desmopressin:** It is also the drug of choice for **Nocturnal Enuresis** and is used in **Von Willebrand Disease (Type 1)** and **Hemophilia A** because it stimulates the release of Factor VIII and vWF from endothelial cells. * **Diagnosis:** To differentiate Central from Nephrogenic DI, a **Water Deprivation Test** followed by Desmopressin administration is used; a significant increase in urine osmolality indicates Central DI.

Q: Which of the following is given at intervals as a pulsatile therapy?

GnRH. **Explanation:** The correct answer is **GnRH (Gonadotropin-Releasing Hormone)**. **1. Why GnRH is the correct answer:** The physiological secretion of GnRH from the hypothalamus is naturally **pulsatile**. In clinical practice, the therapeutic effect of GnRH depends entirely on its mode of administration: * **Pulsatile administration:** Mimics physiological release and is used to **stimulate** the pituitary to release FSH and LH. This is used to treat infertility and delayed puberty (e.g., Kallmann syndrome). * **Continuous (Continuous/Non-pulsatile) administration:** Leads to **downregulation** and desensitization of GnRH receptors on pituitary gonadotropes, causing a "medical castration" effect. This is used in treating prostate cancer, endometriosis, and precocious puberty. **2. Why other options are incorrect:** * **GH (Growth Hormone):** While GH is naturally secreted in pulses (mainly at night), therapeutic GH is typically administered as a once-daily subcutaneous injection to maintain steady levels for growth stimulation. * **FSH (Follicle-Stimulating Hormone):** In ovulation induction protocols, FSH is given in a steady daily dose to promote follicular recruitment rather than in a pulsatile manner. * **Estrogen:** Estrogen is administered continuously (or cyclically in HRT/OCPs) to maintain systemic levels; it does not require pulsatile delivery to exert its biological effects. **High-Yield Clinical Pearls for NEET-PG:** * **GnRH Agonists (e.g., Leuprolide, Goserelin):** Initially cause a "flare-up" of symptoms due to a transient rise in LH/FSH before downregulation occurs. * **GnRH Antagonists (e.g., Cetrorelix, Degarelix):** Provide immediate suppression without the initial flare-up. * **Diagnostic Use:** Pulsatile GnRH can be used to differentiate between hypothalamic (responds to GnRH) and pituitary (does not respond) causes of hypogonadism.

Q: Which of the following drugs is NOT used for the treatment of osteoporosis?

Steroids. **Explanation:** The correct answer is **Steroids**. In fact, long-term use of glucocorticoids (steroids) is one of the most common causes of **secondary osteoporosis**. **Why Steroids are the correct answer:** Steroids induce bone loss through multiple mechanisms: 1. **Decreased Bone Formation:** They inhibit osteoblast activity and promote osteocyte apoptosis. 2. **Increased Bone Resorption:** They increase the expression of RANK-L and decrease Osteoprotegerin (OPG), leading to osteoclast activation. 3. **Calcium Imbalance:** They decrease intestinal calcium absorption and increase renal calcium excretion, leading to secondary hyperparathyroidism. **Why the other options are incorrect:** * **Bisphosphonates (e.g., Alendronate, Zoledronate):** These are the **first-line drugs** for osteoporosis. They inhibit osteoclast-mediated bone resorption by binding to hydroxyapatite crystals. * **Denosumab:** This is a monoclonal antibody against **RANK-L**. By inhibiting RANK-L, it prevents the maturation of osteoclasts, thereby increasing bone mineral density. * **Calcium:** Adequate calcium intake (often combined with Vitamin D) is a fundamental component of both prevention and treatment of osteoporosis to maintain bone mineralization. **High-Yield Clinical Pearls for NEET-PG:** * **Teriparatide:** A recombinant PTH analogue; it is the only **anabolic agent** (builds bone) mentioned frequently in exams. * **Raloxifene:** A Selective Estrogen Receptor Modulator (SERM) used for postmenopausal osteoporosis; it has the added benefit of reducing the risk of breast cancer. * **Drug of Choice:** Bisphosphonates remain the DOC for most patients with osteoporosis. * **Side Effect:** A classic side effect of Bisphosphonates is **esophagitis** (patients must stay upright for 30 minutes) and the rare **Osteonecrosis of the Jaw (ONJ)**.

Q: Teriparatide can be used for the treatment of:

Osteoporosis. **Explanation:** **Teriparatide** is a recombinant form of human parathyroid hormone (PTH 1-34). Its primary clinical indication is the treatment of **Osteoporosis** (both postmenopausal and idiopathic/hypogonadal in men), particularly in patients at high risk for fractures. 1. **Why Option A is Correct:** While continuous high levels of endogenous PTH (as seen in hyperparathyroidism) cause bone resorption, **intermittent (once-daily) subcutaneous administration** of Teriparatide has a paradoxical **anabolic effect**. It stimulates osteoblastic activity more than osteoclastic activity, leading to increased bone mineral density (BMD) and improved bone architecture. 2. **Why Other Options are Incorrect:** * **B (Breast Carcinoma):** Teriparatide is not used here. In fact, it is contraindicated in patients with a history of skeletal malignancies or bone metastases due to the theoretical risk of osteosarcoma. * **C (PCOD):** PCOD is managed with lifestyle changes, OCPs, metformin, or clomiphene. Teriparatide has no role in androgen or insulin regulation. * **D (Hyperparathyroidism):** Teriparatide is an exogenous PTH analogue. Administering it in hyperparathyroidism would worsen the hypercalcemia and bone loss associated with the disease. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Intermittent administration → "Anabolic Window" (Bone formation > Resorption). * **Black Box Warning:** Risk of **Osteosarcoma** (observed in rat studies); hence, it is usually restricted to a maximum lifetime use of 2 years. * **Contraindications:** Paget’s disease of bone, unexplained elevation of alkaline phosphatase, prior radiation therapy to the skeleton, and skeletal malignancies. * **Side Effects:** Hypercalcemia (transient), leg cramps, and dizziness.

Q: Which of the following agents is not used in the management of Cushing syndrome?

Amoxapine. **Explanation:** The management of Cushing syndrome involves inhibiting the overproduction of cortisol. This is achieved through adrenal steroidogenesis inhibitors, adrenolytic agents, or neuromodulators. **Why Amoxapine is the correct answer:** **Amoxapine** is a **Tricyclic Antidepressant (TCA)** primarily used in the treatment of major depressive disorders. It has no role in the suppression of the hypothalamic-pituitary-adrenal (HPA) axis or the inhibition of steroid enzymes. Therefore, it is not used in the management of Cushing syndrome. **Analysis of incorrect options:** * **Mitotane (Option A):** An adrenolytic agent that causes selective destruction of the adrenal cortex (specifically the zona fasciculata and reticularis). It is used primarily in adrenal carcinoma. * **Etomidate (Option B):** An intravenous anesthetic agent that, even at sub-hypnotic doses, is a potent inhibitor of **11β-hydroxylase**. It is used in the emergency management of severe hypercortisolism. * **Metyrapone (Option C):** A selective inhibitor of **11β-hydroxylase**, which blocks the final step of cortisol synthesis. It is frequently used for diagnostic testing and medical management of Cushing syndrome. **NEET-PG High-Yield Pearls:** * **Ketoconazole:** The most commonly used medical therapy for Cushing syndrome; it inhibits multiple enzymes (CYP17, 11β-hydroxylase, and side-chain cleavage). * **Mifepristone:** A glucocorticoid receptor antagonist used to treat hyperglycemia secondary to Cushing syndrome. * **Pasireotide:** A somatostatin analog used specifically for **Cushing Disease** (pituitary etiology) by inhibiting ACTH secretion. * **Drug of choice for medical management:** Ketoconazole is often preferred due to its efficacy and availability.

Q: Which of the following agents causes relaxation of the uterus to delay labor?

Ritodrine. **Explanation:** The correct answer is **Ritodrine**. **1. Why Ritodrine is correct:** Ritodrine is a **selective $\beta_2$-adrenergic agonist**. In the uterus, $\beta_2$ receptors are responsible for smooth muscle relaxation (tocolysis). When stimulated, these receptors increase intracellular cAMP, which inhibits myosin light chain kinase, leading to decreased uterine contractions. Ritodrine is specifically used as a **tocolytic agent** to delay premature labor [1], allowing time for the administration of corticosteroids (to accelerate fetal lung maturity). **2. Why the other options are incorrect:** * **Tolterodine:** This is a competitive **muscarinic (M3) receptor antagonist** used primarily for overactive bladder and urge incontinence. It acts on the detrusor muscle, not the uterine smooth muscle. * **Oxytocin:** This is a peptide hormone that **stimulates uterine contractions** (oxytocic) [2]. It is used for the induction of labor and the management of postpartum hemorrhage (PPH) [2]. * **Labetalol:** This is a combined **$\alpha_1$ and non-selective $\beta$ blocker**. While it is a first-line agent for pregnancy-induced hypertension (PIH), it does not cause uterine relaxation. **3. NEET-PG High-Yield Pearls:** * **Tocolytic of Choice:** Currently, **Nifedipine** (Calcium Channel Blocker) or **Atosiban** (Oxytocin antagonist) are often preferred over Ritodrine due to a better side-effect profile [1]. * **Side Effects of $\beta_2$ Agonists:** Maternal tachycardia, palpitations, hypokalemia, and pulmonary edema. * **Other Tocolytics:** Magnesium sulfate (neuroprotection) [1], Indomethacin (NSAID - can cause premature closure of ductus arteriosus). * **Mnemonic for Tocolytics:** "**I**t's **N**ot **M**y **T**ime" (**I**ndomethacin, **N**ifedipine, **M**agnesium sulfate, **T**erbutaline/Ritodrine).

Question 1

What is the drug of choice for central diabetes insipidus?

Accepted Answer

Desmopressin

Answer

Vasopressin

Answer

Lypressin

Answer

Presselin

Question 2

A 55-year-old woman undergoing tamoxifen therapy for breast cancer presents with vaginal bleeding. What is the best explanation for this symptom?

Accepted Answer

Tamoxifen has an antagonist effect on the breast but an agonist effect on the uterus.

Answer

Tamoxifen acts as an estrogen antagonist in both the breast and uterus, leading to a loss of endometrial cells.

Answer

Tamoxifen has an estrogen agonist effect on both the breast and uterus, leading to endometrial hyperplasia.

Answer

Tamoxifen has no effect on the uterus, and the vaginal bleeding is caused by an unrelated condition.

Question 3

Which of the following is given at intervals as a pulsatile therapy?

Accepted Answer

GnRH

Answer

GH

Answer

PSH

Answer

Estrogen

Question 4

Which of the following drugs is NOT used for the treatment of osteoporosis?

Accepted Answer

Steroids

Answer

Bisphosphonates

Answer

Denosumab

Answer

Calcium

Question 5

Teriparatide can be used for the treatment of:

Accepted Answer

Osteoporosis

Answer

Hormone responsive breast carcinoma

Answer

Polycystic ovarian disease

Answer

Hyperparathyroidism

Question 6

Which of the following agents is not used in the management of Cushing syndrome?

Accepted Answer

Amoxapine

Answer

Mitotane

Answer

Etomidate

Answer

Metyrapone

Question 7

In diabetes mellitus with increased HbA1c, which of the following is NOT a drug used in treatment?

Accepted Answer

Acarbose

Answer

Sulfonylureas

Answer

Biguanides

Answer

Thiazolidinediones

Question 8

Which of the following statements is TRUE regarding adrenal suppression caused by steroid therapy?

Accepted Answer

Adrenal suppression is less likely to occur in patients receiving inhaled steroids.

Answer

Adrenal suppression is not associated with atrophy of the adrenal glands.

Answer

Adrenal suppression should be expected in anyone receiving more than 5 mg of prednisolone daily.

Answer

Following cessation of steroid therapy, the stress response normalizes after 8 weeks.

Question 9

Which oral hypoglycemic agent causes the maximum hypoglycemia?

Accepted Answer

Sulfonylureas

Answer

Metformin

Answer

Miglitol

Answer

Pioglitazone

Question 10

Which of the following agents causes relaxation of the uterus to delay labor?

Accepted Answer

Ritodrine

Answer

Tolterodine

Answer

Oxytocin

Answer

Labetalol

Endocrine Pharmacology — MCQs

Endocrine Pharmacology — MCQs

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