Endocrinology — MCQs

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 121: At what value of a one-hour glucose challenge test would you recommend a standard glucose tolerance test?

A. 120 mg/dL
B. 140 mg/dL (Correct Answer)
C. 150 mg/dL
D. 160 mg/dL

Explanation: This question pertains to the screening protocol for **Gestational Diabetes Mellitus (GDM)** using the two-step approach (Carpenter-Coustan criteria). ### **Explanation** The screening process typically begins between **24 and 28 weeks of gestation** with a **50g Glucose Challenge Test (GCT)** [1]. This is a non-fasting test where plasma glucose is measured one hour after glucose ingestion [1]. * **The Threshold:** A value of **≥140 mg/dL (7.8 mmol/L)** is the standard cutoff used to identify women at high risk. If the GCT result meets or exceeds this value, the test is considered "positive" (abnormal), and the patient must proceed to the diagnostic **100g, 3-hour Oral Glucose Tolerance Test (OGTT)**. * *Note:* Some clinicians use a lower cutoff of 130 mg/dL to increase sensitivity, but 140 mg/dL remains the most widely tested standard in medical examinations. ### **Analysis of Incorrect Options** * **A. 120 mg/dL:** This value is too low and falls within the normal postprandial range for many individuals; using this would result in an excessive number of false positives. * **C. 150 mg/dL & D. 160 mg/dL:** While these values are certainly abnormal, they are too high to serve as a primary screening cutoff [2]. Using these would miss a significant percentage of women with GDM (low sensitivity). ### **High-Yield Clinical Pearls for NEET-PG** * **DIPSI Guidelines:** In India, the DIPSI (Diabetes in Pregnancy Study Group India) recommends a **single-step** procedure: 75g glucose load regardless of fasting status. A 2-hour value **≥140 mg/dL** is diagnostic of GDM. * **O'Sullivan's Criteria:** If the 1-hour GCT is **>200 mg/dL**, GDM is diagnosed directly without needing a follow-up OGTT [2]. * **Risk Factors:** Screening should be done at the **first prenatal visit** if the patient is obese, has a history of GDM, or has a strong family history of Type 2 Diabetes.

Question 122: What is the most common cause of Addison's disease?

A. Autoimmune adrenalitis (Correct Answer)
B. Meningococcal septicemia
C. Malignancy
D. Tuberculosis

Explanation: **Explanation:** **Addison’s Disease (Primary Adrenal Insufficiency)** occurs when the adrenal cortex is destroyed, leading to a deficiency of glucocorticoids, mineralocorticoids, and adrenal androgens [1][2]. 1. **Why Autoimmune Adrenalitis is Correct:** In developed countries and globally as a whole, **Autoimmune Adrenalitis** is the most common cause (responsible for ~80% of cases). It involves the production of antibodies against the enzyme **21-hydroxylase**, leading to lymphocytic infiltration and atrophy of the adrenal cortex. It often occurs as part of Autoimmune Polyendocrine Syndromes (APS Type 1 and 2) [1]. 2. **Analysis of Incorrect Options:** * **Tuberculosis (D):** Historically, TB was the leading cause [2]. It remains a significant cause in developing countries (like India), but globally, it has been overtaken by autoimmune etiology. On imaging, TB typically shows **adrenal enlargement with calcification** [1], whereas autoimmune disease shows atrophic glands. * **Meningococcal Septicemia (B):** This causes acute adrenal insufficiency due to bilateral adrenal hemorrhage, known as **Waterhouse-Friderichsen Syndrome**. It is an acute crisis rather than the chronic presentation of Addison’s. * **Malignancy (C):** Metastatic spread (commonly from lung or breast cancer) can destroy the adrenal glands, but this is a much rarer cause compared to autoimmune destruction [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Hyperpigmentation:** A hallmark of primary adrenal insufficiency (due to increased ACTH/MSH), seen specifically in skin creases, buccal mucosa, and scars. * **Electrolyte Triad:** Hyponatremia, Hyperkalemia, and Metabolic Acidosis. * **Screening Test:** ACTH Stimulation Test (Cosyntropin test) is the gold standard for diagnosis [3]. * **Treatment:** Glucocorticoid (Hydrocortisone) and Mineralocorticoid (Fludrocortisone) replacement [1]. Stress doses are required during surgery or infection [3].

Question 123: A patient presents with shock and is suspected to have hypoglycemia. What is the primary basis for treatment?

A. Administer intravenous glucose after clinical assessment.
B. Check for urine sugar.
C. Measure blood glucose levels. (Correct Answer)
D. Establish intravenous access.

Explanation: **Explanation:** In any patient presenting with altered sensorium or shock, **hypoglycemia** is a critical "can't-miss" diagnosis. The primary basis for treatment is the **biochemical confirmation of low blood glucose levels.** [1] 1. **Why Option C is Correct:** According to **Whipple’s Triad**, the diagnosis of hypoglycemia requires: (1) Symptoms consistent with hypoglycemia, (2) A low plasma glucose concentration, and (3) Relief of symptoms after the glucose level is raised. In an emergency setting, a rapid bedside capillary blood glucose (CBG) test is the standard of care to confirm the diagnosis before or during the initiation of therapy to avoid unnecessary glucose loading or misdiagnosis. [1] 2. **Why Other Options are Incorrect:** * **Option A:** While IV glucose is the treatment, administering it *before* any assessment or confirmation can be counterproductive if the shock is due to other causes (e.g., intracranial hemorrhage), where hyperglycemia might worsen neuronal injury. * **Option B:** Urine sugar is irrelevant in hypoglycemia; it is used to screen for glycosuria in hyperglycemia/diabetes. * **Option D:** Establishing IV access is a supportive step, but it is not the "basis for treatment" or the diagnostic priority. **Clinical Pearls for NEET-PG:** * **Whipple’s Triad:** Essential for diagnosing true hypoglycemia. * **Neuroglycopenic symptoms:** Occur at glucose levels <50–55 mg/dL (confusion, seizure, coma). * **Drug of Choice:** In an unconscious patient, **100 ml of 25% Dextrose** or **50 ml of 50% Dextrose** IV is the standard emergency bolus. [2] * **Glucagon:** Can be given IM/SC if IV access is unavailable, but it is ineffective in starved patients or those with liver disease (depleted glycogen stores).

Question 124: Which of the following is NOT a feature of tumour lysis syndrome?

A. Hyperuricemia
B. Hypocalcemia
C. Hyperphosphatemia
D. Hypernatremia (Correct Answer)

Explanation: Explanation: Tumor Lysis Syndrome (TLS) is a metabolic emergency caused by the rapid breakdown of malignant cells, typically following chemotherapy for high-grade hematologic malignancies (e.g., Burkitt lymphoma, ALL). When cells lyse, they release their intracellular contents into the systemic circulation. Why Hypernatremia is the Correct Answer: Hypernatremia is not a feature of TLS. Sodium is the primary extracellular cation; therefore, the destruction of cells does not significantly increase serum sodium levels. In fact, aggressive hydration (the mainstay of TLS management) may sometimes lead to dilutional hyponatremia [1], but hypernatremia is not part of the classic metabolic triad. Why the other options are incorrect (Features of TLS): * Hyperuricemia (A): Catabolism of purines from released nucleic acids leads to high uric acid levels [2], which can cause acute kidney injury (urate nephropathy). * Hyperphosphatemia (C): Malignant cells contain significantly higher concentrations of intracellular phosphorus than normal cells. Rapid release leads to hyperphosphatemia. * Hypocalcemia (B): This is a secondary phenomenon. Excess phosphorus binds to serum calcium, forming calcium-phosphate crystals that deposit in soft tissues and the kidneys, leading to a drop in ionized calcium. * Hyperkalemia: (Though not an option, it is a hallmark) Release of intracellular potassium can lead to life-threatening arrhythmias. Clinical Pearls for NEET-PG: * Cairo-Bishop Definition: Used to classify laboratory vs. clinical TLS. * Prophylaxis: Aggressive IV hydration and Allopurinol (xanthine oxidase inhibitor). * Treatment of Choice for Hyperuricemia: Rasburicase (recombinant urate oxidase) which converts uric acid to the highly soluble allantoin. * The "TLS Triad + 1": Hyperkalemia, Hyperphosphatemia, Hyperuricemia, and Hypocalcemia.

Question 125: A 23-year-old female air force officer notes a lower pitch to her voice, coarsening of her hair, an increased tendency toward weight gain, menorrhagia, and increasing intolerance to cold. Which of the following laboratory abnormalities is expected?

A. Increased serum free T4
B. Increased serum T3 resin uptake
C. Increased saturation of thyroid hormone-binding sites on TBG
D. Increased serum TSH (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Increased serum TSH** **Analysis of the Clinical Scenario:** The patient presents with classic signs and symptoms of **Primary Hypothyroidism**: * **Metabolic slowing:** Weight gain and cold intolerance [3]. * **Dermatological/Adnexal changes:** Coarsening of hair and deepening of the voice (due to glycosaminoglycan deposition in the larynx). * **Gynecological:** Menorrhagia (common in hypothyroidism due to altered coagulation factors and impaired estrogen metabolism). In **Primary Hypothyroidism**, the thyroid gland fails to produce sufficient thyroid hormones (T4 and T3). The loss of negative feedback on the pituitary gland leads to a compensatory **increase in Serum TSH** (Thyroid Stimulating Hormone) [1], [2]. This is the most sensitive initial screening test for the condition. **Why the other options are incorrect:** * **A. Increased serum free T4:** This is seen in hyperthyroidism. In primary hypothyroidism, free T4 is low or low-normal [1]. * **B. Increased serum T3 resin uptake:** T3 resin uptake (T3RU) measures the available binding sites on Thyroid-Binding Globulin (TBG). In hypothyroidism, there are more empty binding sites because T4 levels are low; therefore, T3RU is **decreased**. (Increased T3RU is seen in hyperthyroidism or states with low TBG). * **C. Increased saturation of TBG:** Since the total amount of circulating thyroid hormone is low in hypothyroidism, the percentage of TBG saturated with hormone is **decreased**, not increased. **NEET-PG High-Yield Pearls:** * **Screening:** Serum TSH is the best initial and most sensitive test for primary hypothyroidism. * **Subclinical Hypothyroidism:** Defined as elevated TSH with a **normal** free T4 level. * **Wolff-Chaikoff Effect:** Autoregulation where a large iodine load inhibits thyroid hormone synthesis; can lead to hypothyroidism. * **Anemia in Hypothyroidism:** Most commonly **Normocytic Normochromic**, but can be Macrocytic (due to associated Pernicious Anemia or decreased metabolism).

Question 126: What is the single best test for the diagnosis of hypothyroidism?

A. T3
B. T4
C. TSH (Correct Answer)
D. RAIU

Explanation: The diagnosis of hypothyroidism primarily relies on the hypothalamic-pituitary-thyroid axis [1]. **Serum TSH (Thyroid Stimulating Hormone)** is the single best, most sensitive, and most specific screening test for both primary hypothyroidism and hyperthyroidism [1], [2]. Due to the inverse logarithmic relationship between TSH and free T4, even a minor decrease in thyroid hormone levels triggers a significant compensatory rise in TSH, making it the earliest marker of thyroid dysfunction [1]. **Why other options are incorrect:** * **T4 (Thyroxine):** While Free T4 is used to confirm the diagnosis and assess severity, it is less sensitive than TSH [2]. In "Subclinical Hypothyroidism," TSH is elevated while T4 remains within the normal range [1]. * **T3 (Triiodothyronine):** This is the least useful test for hypothyroidism [1]. T3 levels often remain within the normal range until late stages of the disease due to increased peripheral conversion of T4 to T3 and preferential secretion of T3 by the failing gland. * **RAIU (Radioactive Iodine Uptake):** This test measures the metabolic activity of the gland. It is primarily used in the differential diagnosis of **hyperthyroidism** (e.g., Graves' vs. Thyroiditis) and has no role in the routine diagnosis of hypothyroidism. **High-Yield Clinical Pearls for NEET-PG:** * **Best Screening Test:** TSH. * **Best test to monitor Levothyroxine therapy:** TSH (target 0.5–2.5 mIU/L). * **Exception:** In **Secondary (Central) Hypothyroidism**, TSH is unreliable (may be low, normal, or slightly high but non-functional) [2]. Here, **Free T4** is the best test for diagnosis and monitoring [2]. * **Subclinical Hypothyroidism:** Elevated TSH with Normal Free T4 [1].

Question 127: A 30-year-old woman is evaluated for fatigue and found to have a low serum thyroxine level. Five years ago, she was treated for Graves' disease with radioactive iodine. What is the diagnostic test of choice?

A. Serum TSH (Correct Answer)
B. Serum T3
C. TRH stimulation test
D. Radioactive iodine uptake

Explanation: The patient presents with symptoms and biochemical evidence of hypothyroidism (low T4) following definitive treatment for Graves' disease with radioactive iodine (RAI). RAI therapy frequently leads to permanent primary hypothyroidism due to the destruction of thyroid follicular cells. **1. Why Serum TSH is the Correct Answer:** In **primary hypothyroidism**, the pituitary gland responds to low circulating thyroid hormones (T3/T4) by increasing the secretion of Thyroid Stimulating Hormone (TSH) via the negative feedback loop [1]. **Serum TSH is the most sensitive and specific screening and diagnostic test** for primary hypothyroidism. An elevated TSH in the presence of low free T4 confirms the diagnosis. **2. Why Incorrect Options are Wrong:** * **Serum T3:** T3 levels are often the last to drop in hypothyroidism. Many patients with overt hypothyroidism may have T3 levels within the normal range due to increased TSH-induced conversion of T4 to T3 [1]. It is not a reliable diagnostic tool for hypothyroidism. * **TRH Stimulation Test:** This was historically used to diagnose secondary (central) hypothyroidism or subclinical hyperthyroidism. With modern, highly sensitive 3rd generation TSH assays, this test is rarely required in clinical practice [1]. * **Radioactive Iodine Uptake (RAIU):** RAIU measures the *function* of the gland (useful in differentiating causes of hyperthyroidism). In a patient who has already received RAI therapy, the gland is fibrotic/destroyed; RAIU would be low but does not provide a primary diagnosis of the thyroid state. **NEET-PG High-Yield Pearls:** * **Most common cause of hypothyroidism post-Graves' treatment:** Radioactive Iodine ablation (usually occurs within 6–12 months). * **Best Screening Test for Thyroid Dysfunction:** Serum TSH [1]. * **Amiodarone:** Can cause both hypothyroidism (Wolff-Chaikoff effect) and hyperthyroidism (Jod-Basedow phenomenon). * **Subclinical Hypothyroidism:** Elevated TSH with a **normal** Free T4 [1]. Treatment is generally indicated if TSH >10 mIU/L or if the patient is pregnant.

Question 128: Raised calcium and phosphorus are seen in which of the following conditions?

A. Chronic renal failure (CRF)
B. Vitamin D intoxication (Correct Answer)
C. Hyperparathyroidism
D. Pseudohypoparathyroidism

Explanation: ### Explanation The correct answer is **Vitamin D intoxication**. **1. Why Vitamin D Intoxication is Correct:** Vitamin D (specifically its active form, Calcitriol) acts on three main sites to regulate mineral homeostasis: [1] * **Intestine:** It significantly increases the absorption of both **Calcium and Phosphorus**. * **Bone:** In high doses, it promotes bone resorption, releasing both minerals into the ECF. * **Kidneys:** It increases the reabsorption of Calcium and Phosphorus in the distal tubules. Consequently, an excess of Vitamin D leads to simultaneous **Hypercalcemia** and **Hyperphosphatemia**, along with symptoms like thickening of long bones and calcification of soft tissues. [1] **2. Why the Other Options are Incorrect:** * **Chronic Renal Failure (CRF):** Characterized by **Hypocalcemia** (due to decreased 1-alpha-hydroxylase activity/low Calcitriol) and **Hyperphosphatemia** (due to decreased renal excretion). * **Hyperparathyroidism:** Parathyroid hormone (PTH) increases Calcium but is **phosphaturic**. It decreases proximal tubular reabsorption of phosphate, leading to **Hypercalcemia** and **Hypophosphatemia**. * **Pseudohypoparathyroidism:** This is a state of PTH resistance. It mimics hypoparathyroidism, resulting in **Hypocalcemia** and **Hyperphosphatemia**. **3. NEET-PG High-Yield Pearls:** * **The "Rule of Reciprocity":** Usually, Calcium and Phosphorus move in opposite directions (e.g., PTH action). Vitamin D is the notable exception where both move in the **same** direction. * **Sarcoidosis:** Patients with Sarcoidosis develop hypercalcemia and hyperphosphatemia because macrophages in granulomas contain 1-alpha-hydroxylase, which converts Vitamin D to its active form uncontrollably. * **Milk-Alkali Syndrome:** Another cause of high calcium and high phosphorus, often associated with metabolic alkalosis and renal failure.

Question 129: Which of the following urinary metabolites are most sensitive for the diagnosis of pheochromocytomas?

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

Explanation: **Explanation:** The diagnosis of **Pheochromocytoma** (a catecholamine-secreting tumor of the adrenal medulla) relies on demonstrating excess catecholamine production [2]. **Why Metanephrines are the correct answer:** Metanephrines (normetanephrine and metanephrine) are the intermediate metabolites of catecholamines [2]. Within the tumor cells, the enzyme **Catechol-O-methyltransferase (COMT)** continuously converts catecholamines into metanephrines. This process occurs independently of the episodic release of hormones into the bloodstream. Consequently, metanephrines are produced and leaked into the circulation/urine continuously, making them the **most sensitive** marker (sensitivity ~97-99%) for diagnosis. **Analysis of Incorrect Options:** * **A. Vanillylmandelic acid (VMA):** VMA is the end-product of catecholamine metabolism. While highly specific, it has **low sensitivity** because its levels only rise significantly during periods of massive catecholamine release. It is no longer the first-line screening test. * **C & D. 5-HIAA and 5-HTP:** These are metabolites of **serotonin**. They are used in the diagnosis of **Carcinoid Syndrome**, not pheochromocytoma. **NEET-PG High-Yield Pearls:** * **Screening Test of Choice:** Plasma free metanephrines (highest sensitivity). * **Confirmatory Test:** 24-hour urinary fractionated metanephrines and catecholamines. * **Rule of 10s:** 10% are bilateral, 10% are malignant, 10% are extra-adrenal (Paragangliomas), and 10% occur in children. * **Clinical Triad:** Episodic headache, sweating (diaphoresis), and tachycardia/palpitations. * **Pre-operative Management:** Always give **Alpha-blockers first** (e.g., Phenoxybenzamine) followed by Beta-blockers to prevent a hypertensive crisis [1].

Question 130: Advanced bone age is seen in all conditions except which of the following?

A. Marfan's syndrome (Correct Answer)
B. Congenital adrenal hyperplasia
C. Precocious puberty
D. Obesity

Explanation: **Explanation:** Bone age is a measure of skeletal maturity, typically assessed via X-ray of the left hand and wrist. **Advanced bone age** occurs when skeletal maturation is faster than chronological age, usually due to early or excessive exposure to sex steroids or growth-promoting hormones. [1] **Why Marfan’s Syndrome is the Correct Answer:** In **Marfan’s syndrome**, patients exhibit tall stature and arachnodactyly due to a genetic defect in fibrillin-1, which leads to connective tissue laxity and longitudinal overgrowth of long bones. However, this is a structural/skeletal dysplasia rather than a hormonal maturation issue. Consequently, the **bone age in Marfan’s syndrome is typically normal** (concordant with chronological age), making it the "except" in this list. **Analysis of Incorrect Options:** * **Congenital Adrenal Hyperplasia (CAH):** Excess adrenal androgens cause rapid linear growth initially but lead to premature closure of epiphyseal plates. This results in significantly **advanced bone age**. * **Precocious Puberty:** Early secretion of estrogen or testosterone triggers premature skeletal maturation and epiphyseal fusion, leading to **advanced bone age**. * **Obesity:** Childhood obesity is associated with increased levels of insulin and leptin, and the peripheral conversion of androgens to estrogens in adipose tissue. This often leads to accelerated linear growth and **advanced bone age**. **High-Yield Clinical Pearls for NEET-PG:** * **Delayed Bone Age:** Seen in Constitutional Delay of Growth and Puberty (CDGP), Hypothyroidism, Growth Hormone deficiency, and Malnutrition. * **Advanced Bone Age:** Seen in CAH, Precocious puberty, Hyperthyroidism, and Exogenous androgen/estrogen exposure. * **Rule of Thumb:** If a child is tall for their age but has an advanced bone age, their final adult height potential is often reduced due to early epiphyseal fusion. [1]

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