Endocrinology Practice Questions

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

Metanephrines. **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].

Q: A 36-year-old female presents with symptoms of hyperparathyroidism, a tumor in the pancreas, adrenal cortical hyperplasia, pituitary adenomas, an islet cell tumor, and cutaneous angiofibromas. What is the diagnosis?

Multiple Endocrine Neoplasia Type I (MEN I). The patient presents with the classic triad of **Multiple Endocrine Neoplasia Type I (MEN 1)**, also known as **Wermer’s Syndrome**. This autosomal dominant condition is caused by a mutation in the *MEN1* gene (encoding the protein Menin). The diagnosis is confirmed by the presence of the **"3 Ps"**: 1. **Parathyroid:** Hyperparathyroidism (most common initial manifestation, usually due to multiglandular hyperplasia). 2. **Pancreas:** Enteropancreatic tumors (e.g., Gastrinomas, Insulinomas, or non-functional islet cell tumors). 3. **Pituitary:** Adenomas (most commonly Prolactinomas). Additionally, MEN 1 is associated with non-endocrine manifestations such as **cutaneous angiofibromas**, collagenomas, lipomas, and **adrenal cortical tumors** (usually non-functional hyperplasia), all of which are present in this clinical vignette. [1] **Why other options are incorrect:** * **MEN 2A (Sipple Syndrome):** Characterized by Medullary Thyroid Carcinoma (MTC), Pheochromocytoma, and Parathyroid hyperplasia. It does not involve the pituitary or pancreas. [1] * **MEN 2B:** Characterized by MTC, Pheochromocytoma, Mucosal neuromas, and Marfanoid habitus. It lacks parathyroid involvement. * **MEN 2C:** This is not a standard clinical classification in current medical literature; MEN 2 is strictly divided into 2A, 2B, and Familial MTC. **High-Yield Clinical Pearls for NEET-PG:** * **Inheritance:** Autosomal Dominant; Gene: *MEN1* (Chromosome 11q13). * **Most common feature:** Primary Hyperparathyroidism (>95% of patients). * **Most common pancreatic tumor:** Gastrinoma (Zollinger-Ellison Syndrome). * **Screening:** Annual biochemical screening (Calcium, PTH, Gastrin, Prolactin) is recommended for first-degree relatives. [1]

Q: What is the treatment of choice for a 52-year-old male with toxic adenoma?

Radioactive iodine. **Explanation:** Toxic Adenoma (Plummer’s Disease) is characterized by a single hyperfunctioning thyroid nodule that autonomously produces thyroid hormones, leading to the suppression of TSH and subsequent "shut down" of the surrounding normal thyroid tissue. **Why Radioactive Iodine (RAI) is the Correct Answer:** In patients over 40–45 years (like this 52-year-old male), **Radioactive Iodine ($I^{131}$)** is the treatment of choice. The underlying medical concept is the **"Selective Uptake"** principle: because the TSH is suppressed, the normal thyroid tissue is inactive and does not take up the iodine. Only the "hot" toxic nodule traps the $I^{131}$, leading to localized destruction of the adenoma while sparing the rest of the gland. This results in a very low risk of post-treatment hypothyroidism compared to Grave’s disease. **Analysis of Incorrect Options:** * **A. Surgical removal (Hemithyroidectomy):** While effective, surgery is generally reserved for younger patients (<40 years), very large nodules causing compressive symptoms, or when malignancy is suspected. * **B. Radiotherapy:** External beam radiation has no role in the management of benign toxic adenomas. * **D. Medical treatment:** Antithyroid drugs (Methimazole/PTU) are used only to achieve a euthyroid state before definitive therapy (RAI or Surgery). They are not a permanent cure because the nodule will resume hyperfunctioning once the medication is stopped. **NEET-PG High-Yield Pearls:** * **Investigation of Choice:** Radionuclide Thyroid Scan (shows a "Hot Nodule" with suppression of the rest of the gland). * **Treatment of Choice ( 40 years):** Radioactive Iodine ($I^{131}$). * **Toxic Multinodular Goiter (TMNG):** Also prefers RAI in elderly, but surgery (Total Thyroidectomy) if the goiter is large or retrosternal.

Q: Which of the following is a parenteral agent used in the management of diabetes mellitus?

Exenatide. **Explanation:** The correct answer is **Exenatide**. **Why Exenatide is correct:** Exenatide is a **GLP-1 Receptor Agonist** (Incretin mimetic). These agents work by stimulating glucose-dependent insulin secretion, suppressing glucagon release, and slowing gastric emptying [1]. Because GLP-1 agonists are peptide-based molecules, they are susceptible to degradation by gastrointestinal enzymes if taken orally. Therefore, they must be administered via **subcutaneous injection** (parenteral route) [1]. **Why the other options are incorrect:** * **Rosiglitazone (Option A):** A Thiazolidinedione (TZD) that acts as a PPAR-gamma agonist to improve insulin sensitivity [1]. It is administered **orally**. * **Repaglinide (Option B):** A Meglitinide (Glinide) that acts as a short-acting insulin secretagogue by closing ATP-sensitive potassium channels. It is administered **orally** before meals. * **Canagliflozin (Option D):** An SGLT-2 inhibitor that prevents glucose reabsorption in the proximal convoluted tubule of the kidney. It is administered **orally**. **High-Yield Clinical Pearls for NEET-PG:** * **Parenteral Antidiabetic Agents:** Include all **Insulins**, **GLP-1 Agonists** (e.g., Liraglutide, Dulaglutide), and **Pramlintide** (an Amylin analogue). * **Exception:** *Semaglutide* is the only GLP-1 agonist currently available in both oral and injectable forms. * **Key Side Effects:** GLP-1 agonists are associated with weight loss (beneficial in obese diabetics) but carry a risk of pancreatitis and are contraindicated in patients with a history of Medullary Thyroid Carcinoma (MTC). * **Weight Neutrality:** Metformin and DPP-4 inhibitors are weight neutral; GLP-1 agonists and SGLT-2 inhibitors promote weight loss; Sulfonylureas, TZDs, and Insulin cause weight gain.

Q: A patient with an endocrine abnormality shows a 'hung up' reflex. Which of the following conditions causes a 'hung up' reflex?

Hypothyroidism. ### Explanation **Correct Answer: C. Hypothyroidism** The **'hung up' reflex** (also known as Woltman’s sign) refers to a delayed relaxation phase of the deep tendon reflexes, most commonly observed in the Achilles tendon (ankle jerk). **Underlying Pathophysiology:** In hypothyroidism, the slowed relaxation is not due to a defect in nerve conduction, but rather a **mechanical delay in the muscle fibers**. Low levels of thyroid hormone lead to: 1. Decreased activity of the **calcium-ATPase pump** (SERCA) in the sarcoplasmic reticulum, which slows the reuptake of calcium required for muscle relaxation. 2. Changes in myosin isoform expression and slowed ATP turnover. **Analysis of Incorrect Options:** * **A. Myxedema:** While myxedema is a severe form of hypothyroidism, the term "Hypothyroidism" (Option C) is the broader, standard clinical diagnosis associated with this sign [1]. In many exams, if both are present, the primary disease state is preferred. * **B. Hyperthyroidism:** This condition typically presents with **brisk or hyperreflexic** deep tendon reflexes due to increased neuromuscular excitability. * **D. Pheochromocytoma:** This catecholamine-secreting tumor causes hypertension and tachycardia; it does not typically affect the relaxation phase of reflexes [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Woltman’s Sign:** Specifically refers to the delayed relaxation in hypothyroidism. * **Differential Diagnosis for Delayed Relaxation:** Besides hypothyroidism, it can be seen in anorexia nervosa, hypothermia, diabetes mellitus (rarely), and with certain drugs like beta-blockers. * **Pendular Knee Jerk:** Contrast this with the "hung up" reflex; pendular jerks are characteristic of **cerebellar lesions**. * **Pseudomyotonia:** Another term sometimes used to describe the slow relaxation phase in hypothyroid patients.

Q: What is the cause of Cushing's disease?

ACTH-producing pituitary tumor. **Explanation:** The distinction between **Cushing’s Syndrome** and **Cushing’s Disease** is a frequent high-yield topic in NEET-PG. Cushing’s Syndrome is the broad clinical state resulting from chronic exposure to excessive glucocorticoids. **Cushing’s Disease** specifically refers to the subset of cases (approximately 70% of endogenous causes) where the hypercortisolism is caused by an **ACTH-secreting pituitary adenoma** (Option A). **Analysis of Options:** * **Option A (Correct):** Cushing’s Disease is defined by a pituitary microadenoma (usually <10mm) that secretes excess ACTH, leading to bilateral adrenal hyperplasia and elevated cortisol. * **Option B (Incorrect):** Adrenal tumors (adenomas or carcinomas) cause ACTH-independent Cushing’s syndrome. In these cases, ACTH levels are suppressed due to negative feedback. * **Option C (Incorrect):** Ectopic ACTH production (often from Small Cell Lung Cancer or Bronchial Carcinoid) causes Cushing’s syndrome, not "Disease." These patients often present with rapid onset, severe hypokalemia, and hyperpigmentation. * **Option D (Incorrect):** Adrenal hyperplasia is a *consequence* of excess ACTH (either pituitary or ectopic), not the primary cause of Cushing’s Disease itself. **High-Yield Clinical Pearls for NEET-PG:** 1. **Screening Test:** 24-hour urinary free cortisol or Low-Dose Dexamethasone Suppression Test (LDDST). 2. **Confirmatory/Localization:** High-Dose Dexamethasone Suppression Test (HDDST) will suppress cortisol in Cushing’s **Disease** but *not* in ectopic ACTH or adrenal tumors. 3. **Gold Standard for Localization:** Inferior Petrosal Sinus Sampling (IPSS) is used if MRI is inconclusive to differentiate pituitary vs. ectopic sources. 4. **Treatment of Choice:** Transsphenoidal Surgery (TSS).

Q: Which of the following conditions causes hypercalcemia with a normal or low parathyroid hormone (PTH) level?

Sarcoidosis. ### Explanation The key to solving this question lies in understanding the **feedback loop** between serum calcium and Parathyroid Hormone (PTH). In a normal physiological state, hypercalcemia should suppress PTH secretion [2]. **1. Why Sarcoidosis is Correct:** Sarcoidosis is a granulomatous disease. Macrophages within the granulomas contain the enzyme **1-alpha-hydroxylase**, which independently converts 25-hydroxyvitamin D into its active form, **1,25-dihydroxyvitamin D (Calcitriol)**. This leads to increased intestinal calcium absorption [2]. The resulting hypercalcemia appropriately **suppresses the parathyroid glands**, leading to low or low-normal PTH levels (PTH-independent hypercalcemia) [2]. **2. Why the Other Options are Incorrect:** * **A & C (Parathyroid Adenoma/Hyperplasia):** These are causes of **Primary Hyperparathyroidism** [1]. Here, the pathology lies within the parathyroid gland itself, which autonomously secretes high levels of PTH despite elevated serum calcium [1]. * **B (Familial Hypocalciuric Hypercalcemia - FHH):** This is caused by an inactivating mutation in the **Calcium-Sensing Receptor (CaSR)** [1]. The parathyroid glands "perceive" normal calcium levels as low, leading to inappropriately **normal or mildly elevated PTH** levels in the presence of hypercalcemia [2]. **3. High-Yield Clinical Pearls for NEET-PG:** * **PTH-Independent Hypercalcemia (Low PTH):** Think of Malignancy (PTHrP), Sarcoidosis/Tuberculosis (Vitamin D mediated), Multiple Myeloma, and Vitamin D toxicity [2]. * **PTH-Dependent Hypercalcemia (High/Normal PTH):** Think of Primary Hyperparathyroidism and FHH [2]. * **Distinguishing FHH from Primary Hyperparathyroidism:** FHH presents with a **Urinary Calcium/Creatinine Clearance Ratio 0.02 in Primary Hyperparathyroidism. * **Sarcoidosis Triad:** Bilateral hilar lymphadenopathy, hypercalcemia, and elevated ACE (Angiotensin-Converting Enzyme) levels.

Question 1

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?

Accepted Answer

Serum TSH

Answer

Serum T3

Answer

TRH stimulation test

Answer

Radioactive iodine uptake

Question 2

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

Accepted Answer

Metanephrines

Answer

Vanillylmandelic acid (VMA)

Answer

5-Hydroxyindoleacetic acid (5HIAA)

Answer

5-Hydroxytryptophan (5HTP)

Question 3

A 20-year-old woman and her twin sister both experience increasing diplopia. Their conditions develop within 3 years of each other. On physical examination, they have exophthalmos and weak extraocular muscle movement. The thyroid gland is diffusely enlarged but painless in each sister, and there is no lymphadenopathy in either woman. Which of the following serum laboratory findings is most likely to be reported in these sisters?

Accepted Answer

Decreased thyroid-stimulating hormone level

Answer

Decreased free thyroxine level

Answer

High titer thyroid peroxidase autoantibodies

Answer

Increased thyrotropin-releasing hormone level

Question 4

Diabetic ketoacidosis is best managed by?

Accepted Answer

Crystalline insulin given intravenously.

Answer

Human insulin given intramuscularly.

Answer

Lente insulin given subcutaneously.

Answer

Isophane insulin given intradermally.

Question 5

A 36-year-old female presents with symptoms of hyperparathyroidism, a tumor in the pancreas, adrenal cortical hyperplasia, pituitary adenomas, an islet cell tumor, and cutaneous angiofibromas. What is the diagnosis?

Accepted Answer

Multiple Endocrine Neoplasia Type I (MEN I)

Answer

Multiple Endocrine Neoplasia Type IIA (MEN 2A)

Answer

Multiple Endocrine Neoplasia Type IIB (MEN 2B)

Answer

Multiple Endocrine Neoplasia Type IIC (MEN 2C)

Question 6

What is the treatment of choice for a 52-year-old male with toxic adenoma?

Accepted Answer

Radioactive iodine

Answer

Surgical removal of the adenoma

Answer

Radiotherapy

Answer

Medical treatment

Question 7

Which of the following is a parenteral agent used in the management of diabetes mellitus?

Accepted Answer

Exenatide

Answer

Rosiglitazone

Answer

Repaglinide

Answer

Canagliflozin

Question 8

A patient with an endocrine abnormality shows a 'hung up' reflex. Which of the following conditions causes a 'hung up' reflex?

Accepted Answer

Hypothyroidism

Answer

Myxedema

Answer

Hyperthyroidism

Answer

Pheochromocytoma

Question 9

What is the cause of Cushing's disease?

Accepted Answer

ACTH-producing pituitary tumor

Answer

Adrenal tumor

Answer

Ectopic production of ACTH

Answer

Adrenal hyperplasia

Question 10

Which of the following conditions causes hypercalcemia with a normal or low parathyroid hormone (PTH) level?

Accepted Answer

Sarcoidosis

Answer

Parathyroid adenoma

Answer

Familial hypocalciuric hypercalcemia

Answer

Parathyroid hyperplasia

Endocrinology — MCQs

Endocrinology — MCQs

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