Endocrinology — MCQs

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 291: Thyroid storm can be treated by all the following drugs except?

A. Propylthiouracil
B. Dexamethasone
C. Propranolol
D. Aspirin (Correct Answer)

Explanation: **Explanation:** Thyroid storm is a life-threatening medical emergency [2] characterized by extreme hypermetabolism. The management focuses on inhibiting thyroid hormone synthesis, blocking hormone release, preventing peripheral conversion of T4 to T3 [2], and controlling sympathetic overactivity [1]. **Why Aspirin is the Correct Answer (Contraindicated):** Aspirin (and other Salicylates) is strictly contraindicated in thyroid storm. It competes with thyroid hormones (T3 and T4) for binding sites on **Thyroid-Binding Globulin (TBG)**. By displacing T4/T3 from these proteins, aspirin increases the levels of **free (active) thyroid hormones** in the serum, which can acutely worsen the clinical features of the storm. **Analysis of Incorrect Options (Used in Treatment):** * **Propylthiouracil (PTU):** The preferred antithyroid drug in storm [3]. It inhibits the enzyme thyroid peroxidase (blocking synthesis) and, crucially, inhibits the **peripheral conversion of T4 to T3**. * **Dexamethasone:** Glucocorticoids are used because they inhibit the peripheral conversion of T4 to T3 and provide coverage for potential relative adrenal insufficiency associated with severe thyrotoxicosis. * **Propranolol:** A non-selective beta-blocker used to control sympathetic symptoms (tachycardia, tremors, agitation) [1]. Like PTU and Steroids, high-dose propranolol also helps decrease T4 to T3 conversion [2]. **NEET-PG High-Yield Pearls:** 1. **Drug of Choice for Fever:** Acetaminophen (Paracetamol) is the preferred antipyretic in thyroid storm. 2. **Sequence of Treatment:** Always give PTU/Methimazole *before* Iodine (Lugol’s solution/SSKI) to prevent the iodine from being used as a substrate for new hormone synthesis (Jod-Basedow phenomenon). 3. **Burch-Wartofsky Point Scale:** The clinical scoring system used to diagnose Thyroid Storm.

Question 292: A patient presents with palpitations, headaches, profuse sweating, and hypertension, raising suspicion for pheochromocytoma. Which diagnostic procedure is NOT typically performed in the evaluation of pheochromocytoma?

A. CT scan
B. MRI
C. FNAC (Fine Needle Aspiration Cytology) (Correct Answer)
D. MIBG scan (Iodine-131 metaiodobenzylguanidine scan)

Explanation: **Explanation:** The diagnosis of pheochromocytoma relies on biochemical confirmation followed by anatomical and functional imaging. **FNAC (Fine Needle Aspiration Cytology)** is strictly **contraindicated** in suspected cases of pheochromocytoma [1]. Performing a needle biopsy on a catecholamine-secreting tumor can trigger a massive, life-threatening release of catecholamines, leading to a "hypertensive crisis," fatal arrhythmias, or hemorrhage. Furthermore, cytology cannot reliably distinguish between benign and malignant adrenal medullary tumors; malignancy is only confirmed by the presence of metastasis to non-chromaffin tissues. **Analysis of Incorrect Options:** * **CT Scan (with non-ionic contrast):** This is usually the initial imaging modality of choice for localization due to its excellent spatial resolution for adrenal masses [2]. * **MRI:** Highly sensitive and preferred in children, pregnant women, or patients with surgical clips [2]. Pheochromocytomas characteristically show a **"Light Bulb" appearance** (hyperintensity) on T2-weighted images. * **MIBG Scan:** A functional imaging technique using a norepinephrine analogue [2]. It is particularly useful for detecting extra-adrenal tumors (paragangliomas) and metastatic disease [2]. **NEET-PG Clinical Pearls:** * **Rule of 10s:** 10% are bilateral, 10% are extra-adrenal, 10% are malignant, and 10% occur in children. * **Biochemical Screening:** The most sensitive initial test is **plasma free metanephrines**; the most specific is **24-hour urinary metanephrines**. * **Pre-operative Management:** Always start **Alpha-blockade (e.g., Phenoxybenzamine)** before Beta-blockade to avoid an unopposed alpha-mediated hypertensive crisis.

Question 293: Which of the following conditions is NOT associated with weight gain?

A. Pheochromocytoma (Correct Answer)
B. Cushing's syndrome
C. Hypothyroidism
D. Insulin secreting tumor

Explanation: **Explanation:** The correct answer is **Pheochromocytoma**. This condition is characterized by a catecholamine-secreting tumor (usually of the adrenal medulla). Excess epinephrine and norepinephrine increase the basal metabolic rate (BMR) and promote glycogenolysis and lipolysis [2]. Consequently, patients typically present with **weight loss** despite a normal or increased appetite [1], alongside the classic triad of episodic headache, sweating, and tachycardia [1]. **Analysis of Incorrect Options:** * **Cushing’s Syndrome:** Excess cortisol leads to increased gluconeogenesis and adipogenesis. It causes **central obesity** with a characteristic distribution of fat (buffalo hump, moon facies, and supraclavicular fat pads) [1]. * **Hypothyroidism:** A deficiency in thyroid hormones leads to a significant decrease in the BMR. Weight gain in these patients is primarily due to **accumulation of glycosaminoglycans** (myxedema) and water retention, rather than just fat [1]. * **Insulin-secreting tumor (Insulinoma):** High levels of insulin promote anabolic processes and inhibit lipolysis. Patients often experience recurrent hypoglycemia, which triggers compensatory **hyperphagia** (increased eating to relieve symptoms), leading to significant weight gain. **High-Yield Clinical Pearls for NEET-PG:** * **Rule of 10s for Pheochromocytoma:** 10% bilateral, 10% malignant, 10% extra-adrenal (Paraganglioma), and 10% pediatric. * **MEN 2A & 2B:** Always screen for Pheochromocytoma before surgery for Medullary Thyroid Carcinoma to prevent a hypertensive crisis. * **Diagnosis:** The most sensitive initial screening test is **plasma free metanephrines**; the most specific is 24-hour urinary metanephrines.

Question 294: All of the following are increased in pheochromocytomas, except?

A. Vanillylmandelic acid (VMA)
B. Metanephrines
C. 5-Hydroxyindoleacetic acid (5-HIAA) (Correct Answer)
D. Catecholamines

Explanation: **Explanation:** Pheochromocytoma is a catecholamine-secreting tumor arising from the chromaffin cells of the adrenal medulla. To answer this question, one must distinguish between the metabolic pathways of catecholamines and serotonin. **Why 5-HIAA is the correct answer:** **5-Hydroxyindoleacetic acid (5-HIAA)** is the primary end-metabolite of **serotonin**. It is the gold-standard biochemical marker for **Carcinoid Syndrome**, not pheochromocytoma. Since pheochromocytomas secrete epinephrine and norepinephrine (catecholamines), they do not result in elevated levels of 5-HIAA. **Why the other options are incorrect:** * **Catecholamines (Option D):** These are the primary hormones (Epinephrine, Norepinephrine, and occasionally Dopamine) produced by the tumor. Their elevation is the direct cause of the clinical triad of headache, sweating, and palpitations. * **Metanephrines (Option B):** Catecholamines are metabolized within the tumor cells by the enzyme Catechol-O-methyltransferase (COMT) into metanephrines (normetanephrine and metanephrine). **Plasma free metanephrines** are the most sensitive screening test for pheochromocytoma. * **Vanillylmandelic acid (VMA) (Option A):** This is the final breakdown product of both metanephrines and catecholamines. While 24-hour urinary VMA is a classic marker, it is less sensitive than metanephrines due to interference by diet and drugs. **High-Yield Clinical Pearls for NEET-PG:** 1. **Rule of 10s:** 10% bilateral, 10% malignant, 10% pediatric, 10% extra-adrenal (Paragangliomas). 2. **Best Screening Test:** Plasma free metanephrines (High sensitivity). 3. **Best Confirmatory Test:** 24-hour urinary metanephrines and catecholamines (High specificity). 4. **Localization:** Contrast-enhanced CT (CECT) is the initial imaging; **123I-MIBG scan** is used for extra-adrenal or metastatic tumors. 5. **Pre-op Management:** Always give **Alpha-blockers (Phenoxybenzamine)** before Beta-blockers to prevent a hypertensive crisis.

Question 295: All of the following are associated with hypergonadotropic hypogonadism in males, EXCEPT?

A. Viral orchitis
B. Klinefelter's syndrome
C. Kallman's syndrome (Correct Answer)
D. Noonan syndrome

Explanation: ### Explanation The key to answering this question lies in distinguishing between **Primary** and **Secondary** hypogonadism based on the Hypothalamic-Pituitary-Gonadal (HPG) axis [1]. **1. Why Kallmann’s Syndrome is the Correct Answer:** Kallmann’s syndrome is a form of **Hypogonadotropic Hypogonadism** (Secondary Hypogonadism). It is caused by the failure of GnRH-secreting neurons to migrate from the olfactory placode to the hypothalamus. This results in low levels of GnRH, leading to low FSH/LH (hypogonadotropic) and subsequently low testosterone. It is classically associated with **anosmia** or hyposmia due to olfactory bulb hypoplasia. **2. Why the other options are incorrect (Hypergonadotropic Hypogonadism):** In these conditions, the defect is in the **testes (Primary Hypogonadism)**. Because the testes cannot produce testosterone or inhibin, the negative feedback loop is lost, causing the pituitary to secrete high levels of FSH and LH (hypergonadotropic) [1]. * **Viral Orchitis:** Mumps is the most common viral cause. Severe inflammation leads to seminiferous tubule damage and testicular atrophy [3]. * **Klinefelter’s Syndrome (47, XXY):** The most common genetic cause of male hypogonadism [2]. Characterized by testicular dysgenesis, hyalinization of tubules, and elevated gonadotropins [3], [4]. * **Noonan Syndrome:** Often called the "Male Turner Syndrome" (though it affects both sexes). It is an autosomal dominant disorder (mutations in *PTPN11* gene) frequently associated with cryptorchidism and primary gonadal failure [3]. ### High-Yield Clinical Pearls for NEET-PG: * **Kallmann’s Syndrome:** Look for the "Red Flag" triad: **Hypogonadism + Anosmia + Midline defects** (cleft lip/palate). * **Klinefelter’s Syndrome:** Key findings include small firm testes, gynecomastia, long legs (increased crown-to-pubis length), and an increased risk of breast cancer and germ cell tumors [3], [4]. * **Diagnostic Rule:** * Low Testosterone + High LH/FSH = **Primary** (Hypergonadotropic) [3]. * Low Testosterone + Low/Normal LH/FSH = **Secondary** (Hypogonadotropic).

Question 296: Which of the following is NOT a feature of hypercalcemia?

A. Osteitis fibrosa cystica
B. Pathological fractures
C. Pancreatitis
D. All of the above (Correct Answer)

Explanation: Explanation: Hypercalcemia, most commonly caused by Primary Hyperparathyroidism (PHPT) or malignancy, affects multiple organ systems [1]. The classic mnemonic "Stones, Bones, Abdominal Groans, and Psychic Moans" summarizes its clinical presentation. 1. **Bones (Options A & B):** Excess Parathyroid Hormone (PTH) increases osteoclastic activity, leading to bone resorption [1]. This results in **Osteitis fibrosa cystica** (characterized by "brown tumors" and subperiosteal resorption of the phalanges) and **Pathological fractures** due to decreased bone mineral density [1]. 2. **Abdominal Groans (Option C):** Hypercalcemia is a known cause of **Pancreatitis**. High calcium levels can lead to the activation of trypsinogen within the pancreas and the formation of calcium deposits in the pancreatic ducts, triggering inflammation. It is also associated with peptic ulcer disease due to increased gastrin secretion [1]. **Why "All of the above" is correct:** The question asks which of the following is NOT a feature; however, based on the provided key, all listed options (A, B, and C) are actually **well-established features** of hypercalcemia. Therefore, the option "All of the above" serves to confirm that every preceding choice is a valid clinical manifestation of the condition. **High-Yield Clinical Pearls for NEET-PG:** * **ECG Findings:** Hypercalcemia causes a **shortened QT interval**, whereas hypocalcemia causes QT prolongation. * **Renal Effects:** Nephrolithiasis (calcium oxalate stones) and Polyuria (due to nephrogenic diabetes insipidus) are common [1]. * **Most Common Cause:** In outpatients, it is Primary Hyperparathyroidism; in hospitalized patients, it is Malignancy (often via PTHrP) [1]. * **Treatment:** The first-line management for severe hypercalcemia is aggressive **IV hydration with Normal Saline**, followed by loop diuretics (only after rehydration) and Bisphosphonates [1].

Question 297: All of the following conditions are indications for radioactive iodine use, EXCEPT:

A. Age > 40 years
B. Elderly
C. Hyperthyroid children (Correct Answer)
D. Presence of comorbidities

Explanation: **Explanation:** Radioactive Iodine (RAI), specifically **I-131**, is a definitive treatment for hyperthyroidism (Graves' disease or toxic multinodular goiter) [1]. However, its use is governed by specific indications and contraindications based on age and clinical status. **Why "Hyperthyroid children" is the correct answer:** Radioactive iodine is generally **avoided in children and adolescents** (especially those under 10–15 years of age). The primary concerns are the theoretical long-term risk of thyroid carcinoma, potential genetic damage to germ cells, and the high sensitivity of developing tissues to radiation. In pediatric populations, anti-thyroid drugs (ATDs) or surgery are the preferred modalities [1]. **Analysis of incorrect options:** * **Age > 40 years & Elderly:** RAI is often the **treatment of choice** for patients over 40 and the elderly. It provides a permanent cure for hyperthyroidism without the surgical risks associated with anesthesia in older populations. * **Presence of comorbidities:** Patients with significant cardiac disease (e.g., atrial fibrillation, heart failure) or other systemic comorbidities are ideal candidates for RAI. It avoids the physiological stress of surgery while effectively controlling the thyrotoxic state that exacerbates these conditions. **NEET-PG High-Yield Pearls:** * **Absolute Contraindications for RAI:** Pregnancy (risk of fetal thyroid ablation) and Breastfeeding [1]. * **Relative Contraindication:** Active/Moderate-to-severe Graves' Ophthalmopathy (RAI can worsen the condition; steroids are given if RAI is used) [1]. * **Pre-treatment:** In elderly or cardiac patients, it is mandatory to achieve euthyroidism with ATDs *before* giving RAI to prevent a thyroid storm caused by the release of stored hormones. * **Follow-up:** The most common long-term complication of RAI is **hypothyroidism**, requiring lifelong levothyroxine.

Question 298: What is the investigation of choice for hyperprolactinemia?

A. TRH estimation
B. LH estimation
C. Prolactin estimation (Correct Answer)
D. Estradiol estimation

Explanation: ### **Explanation** **Correct Option: C. Prolactin estimation** The diagnosis of hyperprolactinemia is established by the biochemical demonstration of elevated serum prolactin levels [1]. In a patient presenting with symptoms such as galactorrhea, amenorrhea, or infertility (in females) and erectile dysfunction or decreased libido (in males), the **initial and definitive investigation of choice** is a fasting serum prolactin measurement [1]. * **Medical Concept:** Prolactin is secreted by the lactotrophs of the anterior pituitary. A single elevated value is usually sufficient for diagnosis, provided the sample was taken without excessive venipuncture stress. In the presence of a sellar mass lesion, it is crucial that serum prolactin is measured before emergency surgery is performed [1]. **Why other options are incorrect:** * **A. TRH estimation:** While Primary Hypothyroidism can cause hyperprolactinemia (due to increased TRH stimulating prolactin release) [1], TRH estimation is not a routine clinical test. Instead, TSH is measured to rule out thyroid etiology. * **B. LH estimation:** LH levels are often suppressed in hyperprolactinemia due to the inhibition of GnRH pulsatility, but this is a secondary effect and not used for primary diagnosis. * **D. Estradiol estimation:** Similar to LH, estradiol may be low in hyperprolactinemic states [1], but it is non-specific and does not confirm the diagnosis. --- ### **High-Yield Clinical Pearls for NEET-PG** * **Hook Effect:** In cases of giant prolactinomas (>4 cm), extremely high prolactin levels can saturate the assay, leading to a falsely low reading. * **Macroprolactinemia:** If a patient is asymptomatic but has high prolactin, consider "Macroprolactin" (prolactin bound to IgG) [1]. This is biologically inactive. * **Imaging:** Once hyperprolactinemia is confirmed biochemically, the next step to identify the cause (e.g., adenoma) is an **MRI of the Pituitary with Gadolinium** [1]. * **Drug-induced:** Always rule out drugs (especially dopamine antagonists like antipsychotics) which are common causes of mild-to-moderate elevations [1].

Question 299: Hypomagnesemia is associated with which of the following conditions?

A. Alcoholism (Correct Answer)
B. Hypothyroidism
C. Both
D. None

Explanation: Hypomagnesemia is associated with which of the following conditions? **Explanation:** **1. Why Alcoholism is Correct:** Chronic alcoholism is the most common cause of hypomagnesemia in clinical practice. The underlying mechanisms are multifactorial: * **Renal Loss:** Ethanol acts as a direct tubular toxin, causing reversible impairment of magnesium reabsorption in the loop of Henle and distal tubules, leading to hypermagnesuria. * **Nutritional Deficiency:** Alcoholics often have poor dietary intake of magnesium-rich foods. * **Gastrointestinal Loss:** Chronic diarrhea and malabsorption associated with alcoholism further deplete magnesium stores [1]. **2. Why Hypothyroidism is Incorrect:** Hypothyroidism is typically associated with **hypermagnesemia** (mildly elevated magnesium levels). This occurs because thyroid hormones normally promote the renal clearance of magnesium; a deficiency in these hormones leads to increased renal tubular reabsorption. Conversely, *hyperthyroidism* is a known cause of hypomagnesemia due to increased renal excretion. **3. High-Yield Clinical Pearls for NEET-PG:** * **The "Refractory Hypokalemia" Rule:** If a patient has hypokalemia that does not respond to potassium supplementation, always check magnesium levels [1]. Magnesium is a cofactor for the ROMK channels; its deficiency leads to excessive potassium secretion in the distal tubule. * **Hypocalcemia Link:** Severe hypomagnesemia causes hypocalcemia by inducing PTH resistance and inhibiting PTH secretion. * **ECG Findings:** Look for prolonged PR and QT intervals, T-wave flattening, and specifically **Torsades de Pointes** (treated with IV Magnesium Sulfate). * **Other Causes:** Loop/Thiazide diuretics, Aminoglycosides, Amphotericin B, and Cisplatin are frequent pharmacological culprits [1].

Question 300: How is hyperthyroidism diagnosed?

A. Triiodothyronine (T3) and Thyroxine (T4)
B. Triiodothyronine (T3), Thyroxine (T4), and Thyroid Stimulating Hormone (TSH) (Correct Answer)
C. Triiodothyronine (T3), Thyroxine (T4), and Radioactive Iodine Uptake (RAI)
D. Triiodothyronine (T3), Thyroxine (T4), Radioactive Iodine Uptake (RAI), and TSH

Explanation: The diagnosis of hyperthyroidism relies on the biochemical assessment of the hypothalamic-pituitary-thyroid axis. The primary screening and diagnostic tool is the **Serum TSH level**, which is the most sensitive indicator. In primary hyperthyroidism, elevated levels of free **T4 and T3** exert negative feedback on the pituitary, leading to a suppressed TSH (usually <0.01 mU/L) [1]. **Why Option B is correct:** To confirm a diagnosis of hyperthyroidism, one must demonstrate both a suppressed TSH and elevated levels of thyroid hormones (T3 and T4) [3]. Measuring T3 is crucial because, in early Graves' disease or toxic nodules, "T3 toxicosis" may occur where T4 remains normal but T3 is elevated. **Why other options are incorrect:** * **Option A:** Lacks TSH. Without TSH, you cannot distinguish between primary hyperthyroidism and rare secondary causes (TSH-secreting tumors). * **Options C & D:** These include **Radioactive Iodine Uptake (RAI)**. While RAI is essential for determining the **etiology** (e.g., Graves' vs. Thyroiditis), it is not required for the initial biochemical **diagnosis** of the hyperthyroid state itself [2]. **NEET-PG High-Yield Pearls:** * **Best Initial Test:** Serum TSH. * **Subclinical Hyperthyroidism:** Low TSH with normal Free T4 and T3. * **T3 Toxicosis:** Low TSH, normal T4, but high T3 (seen in ~5% of patients). * **Amiodarone:** Can cause both hyperthyroidism (Type 1 or 2) and hypothyroidism (Wolff-Chaikoff effect). * **Pregnancy:** Always use Total T3/T4 (which increase due to TBG) or pregnancy-specific free hormone ranges.

Practice by Chapter

Diabetes Mellitus

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Thyroid Disorders

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Adrenal Gland Disorders

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Pituitary Disorders

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Calcium and Bone Metabolism

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Reproductive Endocrinology

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Lipid Disorders

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Endocrine Hypertension

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Multiple Endocrine Neoplasia

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Obesity and Metabolic Syndrome

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Neuroendocrine Tumors

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Endocrine Emergencies

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