Endocrine Pathology Practice Questions

Q: In malignant hyperthermia, what causes the increased heat production?

Increased muscle metabolism due to excess calcium ions. **Explanation:** **Malignant Hyperthermia (MH)** is a pharmacogenetic hypermetabolic crisis triggered by volatile anesthetics (e.g., Halothane) or depolarizing muscle relaxants (e.g., Succinylcholine). 1. **Why Option A is Correct:** The underlying defect is most commonly a mutation in the **RYR1 (Ryanodine Receptor)** gene on chromosome 19. This receptor regulates the release of calcium from the sarcoplasmic reticulum. In susceptible individuals, triggers cause the RYR1 channel to remain open, leading to a massive **efflux of calcium ions** into the sarcoplasm. This excess calcium causes continuous muscle contraction and overactivation of the ATP-dependent calcium reuptake pumps. The resulting **hypermetabolic state** consumes massive amounts of ATP, generating excessive heat, CO₂, and lactic acid. 2. **Why Other Options are Incorrect:** * **B. Thermic effect of food:** This refers to the energy expenditure required for digestion and is unrelated to anesthetic-induced crises. * **C. Increased sympathetic discharge:** While MH presents with tachycardia and hypertension (mimicking sympathetic overactivity), these are secondary responses to hypercarbia and acidosis, not the primary source of heat. * **D. Mitochondrial thermogenesis:** While mitochondria are involved in cellular respiration, the primary heat source in MH is the mechanical and biochemical work of the myofibrils and ion pumps in the sarcoplasm. **High-Yield Clinical Pearls for NEET-PG:** * **Earliest Sign:** Increase in **End-tidal CO₂ (ETCO₂)**. * **Clinical Features:** Muscle rigidity (specifically Masseter muscle rigidity), hyperpyrexia, and rhabdomyolysis. * **Drug of Choice:** **Dantrolene** (Mechanism: Acts as a muscle relaxant by binding to RYR1 and inhibiting calcium release). * **Inheritance:** Autosomal Dominant.

Q: A 58-year-old woman presents with difficulty in swallowing. After a comprehensive workup by a gastroenterologist rules out primary esophageal disease, she is referred to an endocrinologist. The endocrinologist suspects Riedel thyroiditis. Which of the following physical examination findings would best help confirm this diagnosis?

Very firm thyroid gland. **Explanation:** **Riedel Thyroiditis** is a rare form of chronic thyroiditis characterized by extensive **fibrosis** that replaces the normal thyroid parenchyma and extends into adjacent neck structures (e.g., esophagus, trachea, recurrent laryngeal nerves) [1]. 1. **Why Option D is correct:** The hallmark of Riedel thyroiditis is a **"stony-hard" or "woody" thyroid gland**. This extreme firmness is due to dense fibrous tissue replacement. The fibrosis often extends beyond the capsule, causing obstructive symptoms like dysphagia (difficulty swallowing) or dyspnea, as seen in this patient [1]. 2. **Why other options are incorrect:** * **Option A (Eyeball protrusion):** Exophthalmos is characteristic of **Graves' Disease**, caused by autoimmune-mediated inflammation of orbital tissues, not fibrosis [1]. * **Option B (Massive, soft gland):** A soft or boggy gland is more typical of a simple diffuse goiter. Riedel thyroiditis is never soft; it is fixed and hard [1]. * **Option C (Painful/Tender gland):** Tenderness is the classic feature of **De Quervain (Subacute Granulomatous) Thyroiditis**, which usually follows a viral infection. Riedel thyroiditis is typically painless. **High-Yield Clinical Pearls for NEET-PG:** * **IgG4-Related Disease:** Riedel thyroiditis is now considered part of the systemic IgG4-related sclerosing disease spectrum (associated with retroperitoneal fibrosis and sclerosing cholangitis) [1]. * **"Hard as Wood":** This is the classic descriptor used in exams to differentiate it from Anaplastic Carcinoma, which also presents as a hard, fixed mass in older patients [1]. * **Histology:** Shows dense collagenous fibrous tissue with a sparse lymphocytic infiltrate; importantly, there is **no giant cell formation** (unlike De Quervain). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1091-1092.

Q: A tumor similar to that shown in the illustration is observed in a biopsy specimen from the thyroid of a 50-year-old woman. An adjacent lymph node is also involved. Which of the following descriptions of this tumor is most appropriate?

Slow-growing lesion with relatively good prognosis. ***Slow-growing lesion with relatively good prognosis*** - The histological features described suggest **papillary thyroid carcinoma**, which has an excellent prognosis with **10-year survival rates >95%**. - Despite **lymph node involvement**, papillary carcinoma grows slowly and responds well to **surgical resection** and **radioiodine therapy**. *Functional tumor resulting in thyrotoxicosis* - **Papillary thyroid carcinoma** is typically **non-functional** and does not produce excess thyroid hormones. - Functional tumors causing thyrotoxicosis are usually **toxic adenomas** or **toxic multinodular goiter**, not malignant lesions. *Origin from C cells* - **C cells** (parafollicular cells) give rise to **medullary thyroid carcinoma**, not papillary carcinoma. - Papillary carcinoma originates from **follicular epithelial cells** and shows characteristic **papillary architecture** with **Orphan Annie eye nuclei**. *Calcitonin-producing tumor* - **Calcitonin** is produced by **medullary thyroid carcinoma** arising from C cells, not papillary carcinoma. - Papillary carcinoma produces **thyroglobulin** as a tumor marker, which is used for monitoring recurrence after treatment.

Question 1

Medullary carcinoma of the thyroid arises from which of the following cells?

Accepted Answer

Parafollicular cells

Answer

Cells lining the acini

Answer

Capsule of the thyroid

Answer

Stroma of the gland

Question 2

What is true about papillary carcinoma?

Accepted Answer

Lymph node metastases are common

Answer

Often encapsulated

Answer

Bad prognosis

Answer

Iodine deficiency is an important risk factor

Question 3

Which type of adenoma has the highest propensity to undergo dystrophic calcification?

Accepted Answer

Lactotroph adenoma

Answer

Somatotroph adenoma

Answer

Corticotroph adenoma

Answer

Thyrotroph adenoma

Question 4

A 29-year-old woman presents with a 6-month history of nervousness, muscle weakness, heat intolerance, excessive sweating, and a 9 kg weight loss despite increased caloric intake. She also reports palpitations and amenorrhea. Physical examination reveals warm, moist skin and exophthalmos. A thyroid biopsy is performed. Which of the following best describes the expected pathologic findings?

Accepted Answer

Follicular hyperplasia with scalloping of colloid

Answer

Atrophy and fibrosis

Answer

Dense lymphoid infiltrate with germinal centers

Answer

Necrotizing parenchymal granulomas

Question 5

Pheochromocytoma with malignant potential exclusively secretes which of the following?

Accepted Answer

Dopamine

Answer

Epinephrine

Answer

Metanephrine

Answer

Norepinephrine

Question 6

In malignant hyperthermia, what causes the increased heat production?

Accepted Answer

Increased muscle metabolism due to excess calcium ions

Answer

Thermic effect of food

Answer

Increased sympathetic discharge

Answer

Mitochondrial thermogenesis

Question 7

Familial hypocalciuric hypercalcemia is characterized by mild elevation of calcium and parathyroid hormone (PTH) levels. It is primarily caused by a mutation in which of the following?

Accepted Answer

Mutation of the calcium-sensing receptor (CaSR)

Answer

Missense mutation of the mitochondrial calcium receptor

Answer

Missense mutation of the ribosomal calcium surface protein

Answer

Missense mutation of the Golgi complex receptor

Question 8

A 58-year-old woman presents with difficulty in swallowing. After a comprehensive workup by a gastroenterologist rules out primary esophageal disease, she is referred to an endocrinologist. The endocrinologist suspects Riedel thyroiditis. Which of the following physical examination findings would best help confirm this diagnosis?

Accepted Answer

Very firm thyroid gland

Answer

Eyeball protrusion

Answer

Massive, soft thyroid gland

Answer

Painful and tender thyroid gland

Question 9

A tumor similar to that shown in the illustration is observed in a biopsy specimen from the thyroid of a 50-year-old woman. An adjacent lymph node is also involved. Which of the following descriptions of this tumor is most appropriate?

Accepted Answer

Slow-growing lesion with relatively good prognosis

Answer

Functional tumor resulting in thyrotoxicosis

Answer

Origin from C cells

Answer

Calcitonin-producing tumor

Question 10

Thymic hyperplasia is seen in which condition?

Accepted Answer

Myasthenia gravis

Answer

Thymoma

Answer

Thymic lymphoma

Answer

Scleroderma

Endocrine Pathology — MCQs

Endocrine Pathology — MCQs

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