Thyroid Gland Disorders — MCQs
What is the most common thyroid tumor associated with multiple endocrine neoplasia (MEN)?
Inferior thyroid artery supplies which of the following structures? 1. Thyroid 2. Parathyroid 3. Esophagus 4. Thymus
Which of the following changes in voice is not produced as a result of external laryngeal nerve injury post thyroidectomy?
A 4 cm thyroid nodule that is mobile but causing compressive symptoms presents several considerations. Which of the following statements is false?
What is the treatment of choice for medullary carcinoma of the thyroid?
Which of the following is the initial investigation of choice for a patient presenting with a solitary nodule of the thyroid?
A 23-year-old male patient presents with midline swelling in the neck. The swelling moves with deglutition and protrusion of the tongue. What is the likely diagnosis?
Which of the following conditions is least likely to cause bilateral recurrent laryngeal nerve palsy?
A 55-year-old male patient presents to the clinic with left lower lip weakness following a recent parotid gland surgery. Considering the surgical history and current symptoms, what is the most likely site of the lesion causing this patient's condition?
Which nerve is most commonly injured during submandibular gland surgery?
Thyroid Gland Disorders Indian Medical PG Practice Questions and MCQs
Question 1: What is the most common thyroid tumor associated with multiple endocrine neoplasia (MEN)?
- A. Follicular
- B. Papillary
- C. Anaplastic
- D. Medullary (Correct Answer)
Explanation: ***Medullary*** - The **commonest thyroid tumor** in Multiple Endocrine Neoplasia (MEN) type 2 is medullary thyroid carcinoma, associated with **calcitonin production** [1]. - It arises from **C cells (parafollicular cells)** and is linked to **RET oncogene mutations** in MEN syndromes [1]. *Papillary* - Papillary thyroid carcinoma is the **most common thyroid cancer overall**, but not specifically associated with MEN syndromes. - It typically presents with **lymphatic spread**, whereas medullary carcinoma has a different genetic association. *Follicular* - Follicular thyroid carcinoma is less common in MEN and usually occurs sporadically. - It primarily arises from **follicular cells** and involves a different mechanism than medullary carcinoma. *Anaplastic* - Anaplastic thyroid carcinoma is a rare and highly aggressive form, not commonly associated with MEN. - It usually arises from **differentiated thyroid cancers** and presents in older patients, which does not align with MEN's typical presentations. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1102-1103.
Question 2: Inferior thyroid artery supplies which of the following structures? 1. Thyroid 2. Parathyroid 3. Esophagus 4. Thymus
- A. 1 and 2 only
- B. 1,2 and 3 (Correct Answer)
- C. 1,2 and 4 only
- D. 1,2,3 and 4
Explanation: ***1,2 and 3*** - The **inferior thyroid artery** is a branch of the **thyrocervical trunk** and supplies the **thyroid gland**, **parathyroid glands**, and the **cervical part of the esophagus** [1]. - It also gives branches to the **trachea** and **larynx** (via the inferior laryngeal artery). - These are the standard, consistently described structures supplied by this artery in anatomical texts. *1 and 2 only* - This option is incomplete as the inferior thyroid artery provides blood supply to more structures than just the thyroid and parathyroid glands. - It also supplies the **cervical portion of the esophagus** through its esophageal branches. *1,2 and 4 only* - This option is incorrect because the inferior thyroid artery does supply the **esophagus** (cervical part), which is missing from this option. - The **thymus** is primarily supplied by branches of the **internal thoracic artery**, not the inferior thyroid artery. *1,2,3 and 4* - This option is incorrect because the **thymus** is NOT a standard structure supplied by the inferior thyroid artery. - The thymus receives its blood supply primarily from the **internal thoracic artery** (anterior mediastinal branches) and sometimes from the **superior thyroid artery**. [1] - The inferior thyroid artery's distribution includes thyroid, parathyroid, esophagus, trachea, and larynx—but not the thymus.
Question 3: Which of the following changes in voice is not produced as a result of external laryngeal nerve injury post thyroidectomy?
- A. Inability to sing at higher ranges
- B. Poor volume and projection
- C. Hoarseness (Correct Answer)
- D. Voice fatigue
Explanation: ***Hoarseness*** - **Hoarseness** is primarily caused by injury to the **recurrent laryngeal nerve (RLN)**, which innervates most intrinsic laryngeal muscles responsible for vocal cord adduction and abduction. - An external laryngeal nerve (ELN) injury affects the **cricothyroid muscle**, leading to less tension on the vocal cords, but typically not frank hoarseness. *Voice fatigue* - Injury to the external laryngeal nerve (ELN) weakens the **cricothyroid muscle**, which is responsible for tensing and elongating the vocal cords. - This weakness leads to greater effort required to maintain vocal quality, resulting in **voice fatigue**. *Inability to sing at higher ranges* - The **cricothyroid muscle**, innervated by the ELN, is crucial for increasing vocal cord tension. - Increased tension is necessary for adjusting vocal pitch and reaching **higher frequencies** or notes. *Poor volume and projection* - The cricothyroid muscle's role in vocal cord tension contributes to the efficiency of vocal fold vibration. - Reduced tension due to ELN injury can lead to decreased **vocal power and projection**.
Question 4: A 4 cm thyroid nodule that is mobile but causing compressive symptoms presents several considerations. Which of the following statements is false?
- A. Management may include subtotal thyroidectomy in certain cases.
- B. FNAC cannot reliably distinguish between follicular adenoma and carcinoma.
- C. Cold nodules are always malignant. (Correct Answer)
- D. FNAC is the first-line investigation of choice for thyroid nodules.
Explanation: ***Cold nodules are always malignant.*** - This statement is **false** because while **cold nodules** (those that do not take up radioactive iodine on scintigraphy) have a higher risk of malignancy compared to hot nodules, the vast majority are still **benign**. - Approximately **80-85% of cold nodules are benign**, emphasizing that a cold appearance on scan is an indicator for further investigation, not a definitive diagnosis of cancer. *FNAC is the first-line investigation of choice for thyroid nodules.* - This statement is **true** as fine needle aspiration cytology (**FNAC**) is the **first-line investigation** for evaluating thyroid nodules. - It is minimally invasive, cost-effective, and has high sensitivity and specificity for diagnosing thyroid malignancy. *Management may include subtotal thyroidectomy in certain cases.* - This statement is **true** as **subtotal thyroidectomy** can be considered for **benign multinodular goiter** causing compressive symptoms, especially when total thyroidectomy is deemed too aggressive or increases complication risk. - This approach aims to relieve compression while preserving some thyroid function. *FNAC cannot reliably distinguish between follicular adenoma and carcinoma.* - This statement is **true** because the distinction between a **follicular adenoma** (benign) and a **follicular carcinoma** (malignant) relies on identifying **capsular or vascular invasion**, which cannot be assessed by cytology alone. - A **surgical biopsy** like lobectomy is often required for definitive diagnosis of follicular lesions.
Question 5: What is the treatment of choice for medullary carcinoma of the thyroid?
- A. I-131 ablation
- B. Total thyroidectomy (Correct Answer)
- C. Partial thyroidectomy
- D. Hemithyroidectomy
Explanation: ***Total thyroidectomy*** - This is the **treatment of choice for medullary thyroid carcinoma (MTC)** due to its multifocal nature and high propensity for lymph node metastasis - **Complete surgical resection** (often with central compartment neck dissection) provides the best chance for cure by removing all thyroid tissue and involved lymph nodes - MTC arises from **parafollicular C cells** (calcitonin-producing cells) and frequently involves both lobes, making total thyroidectomy essential *Partial thyroidectomy* - This procedure removes only a portion of the thyroid gland, which is **insufficient for MTC** given its tendency for multifocality and bilateral involvement - Leaves residual thyroid tissue that could harbor undetected disease or develop future recurrences - Does not adequately address the aggressive nature of MTC *I-131 ablation* - **Radioactive iodine therapy** is effective for differentiated thyroid cancers (papillary and follicular) that take up iodine - MTC originates from **parafollicular C cells that do not concentrate iodine**, making I-131 ablation completely ineffective - This is a key distinguishing feature of MTC from other thyroid malignancies *Hemithyroidectomy* - This procedure removes only one thyroid lobe, which is **inadequate for MTC** - Risks leaving behind primary tumor in the contralateral lobe or occult bilateral disease - Fails to address the multifocal nature of MTC, particularly in hereditary cases (MEN 2A, MEN 2B, familial MTC)
Question 6: Which of the following is the initial investigation of choice for a patient presenting with a solitary nodule of the thyroid?
- A. Thyroid function test
- B. FNAC (Correct Answer)
- C. Radionuclide scan
- D. MRI
Explanation: ***FNAC*** - **Fine needle aspiration cytology (FNAC)** is the most important initial investigation for a solitary thyroid nodule to determine if it is benign or malignant. [1] - It offers a highly accurate and minimally invasive method for **cytological analysis** to guide further management. *Thyroid function test* - While important for assessing **thyroid hormone levels** and diagnosing hyper or hypothyroidism, it does not directly evaluate the **malignant potential** of a nodule. [1] - Normal thyroid function does **not rule out malignancy** within a nodule. *Radionuclide scan* - A **radionuclide scan** is useful for assessing the **functional status** of a nodule (hot or cold). [1] - However, non-functional (**cold**) nodules are more suspicious for malignancy, but the scan doesn't provide **histological diagnosis**. *MRI* - **MRI** provides detailed anatomical imaging of the thyroid and surrounding structures but is generally not the **initial diagnostic test of choice** for evaluating a solitary nodule. [1] - It is typically reserved for assessing **nodule extension** or **lymph node involvement** once malignancy is suspected or confirmed. [1]
Question 7: A 23-year-old male patient presents with midline swelling in the neck. The swelling moves with deglutition and protrusion of the tongue. What is the likely diagnosis?
- A. Brachial cyst
- B. Thyroglossal cyst (Correct Answer)
- C. Plunging ranula
- D. Dermoid cyst
Explanation: ***Thyroglossal cyst*** - A **thyroglossal cyst** is a congenital anomaly that arises from the persistent **thyroglossal duct**, a remnant of the thyroid's embryologic descent. - Its classic diagnostic feature is its movement with **deglutition** (due to attachment to the hyoid bone, which moves during swallowing) and **protrusion of the tongue** (as the thyroglossal duct is connected to the base of the tongue). *Brachial cyst* - A **brachial cyst** is a congenital neck mass that typically presents as a lateral neck swelling, often located along the anterior border of the **sternocleidomastoid muscle**. - Unlike a thyroglossal cyst, it does not typically move with **deglutition** or **tongue protrusion**. *Plunging ranula* - A **plunging ranula** is a type of mucocele that arises from the **sublingual gland** and extends below the mylohyoid muscle into the neck. - It presents as a cervical mass but is typically located in the floor of the mouth or submandibular region and does not move with **deglutition** or **tongue protrusion**. *Dermoid cyst* - A **dermoid cyst** is a congenital cyst that can occur anywhere on the body, including the head and neck, often presenting as a painless mass. - It arises from sequestered embryonic ectoderm and mesoderm, containing skin appendages, but it does not move with **deglutition** or **tongue protrusion**.
Question 8: Which of the following conditions is least likely to cause bilateral recurrent laryngeal nerve palsy?
- A. Thyroid carcinoma
- B. Lymphadenopathy
- C. Thyroid surgery
- D. Aortic aneurysm (Correct Answer)
Explanation: ***Aortic aneurysm*** - An aortic aneurysm, especially of the ascending aorta, is **less likely to cause bilateral recurrent laryngeal nerve palsy** because the left recurrent laryngeal nerve typically hooks under the aortic arch, while the right nerve hooks under the subclavian artery. - For **bilateral involvement**, two separate and simultaneous lesions affecting both nerves would be required at different anatomical locations with this etiology, making it a rare cause. *Thyroid carcinoma* - An aggressive **thyroid carcinoma** can directly invade or compress the recurrent laryngeal nerves (RLNs) due to their proximity to the thyroid gland. - If the carcinoma is extensive or multifocal, it can lead to **bilateral involvement** by affecting both nerves. *Lymphadenopathy* - Significant **cervical or mediastinal lymphadenopathy** (e.g., due to metastatic disease or lymphoma) can compress or encase both recurrent laryngeal nerves. - This proximity allows for potential **bilateral compression or damage** to the nerves as they ascend in the tracheoesophageal grooves. *Thyroid surgery* - **Thyroidectomy** is a common cause of recurrent laryngeal nerve injury due to the nerves' close anatomical relationship with the thyroid gland. - **Bilateral recurrent laryngeal nerve palsy** can occur if both nerves are damaged during dissection, often due to surgical misidentification, thermal injury, or traction.
Question 9: A 55-year-old male patient presents to the clinic with left lower lip weakness following a recent parotid gland surgery. Considering the surgical history and current symptoms, what is the most likely site of the lesion causing this patient's condition?
- A. Main trunk of facial nerve
- B. Temporal branch of facial nerve
- C. Parotid duct
- D. Marginal mandibular branch of the facial nerve (Correct Answer)
Explanation: ***Marginal mandibular branch of the facial nerve*** - This branch supplies the muscles around the lower lip, including the **depressor anguli oris** and **depressor labii inferioris**, which are responsible for lower lip movement. - Damage to this specific branch during **parotid gland surgery** is a common cause of isolated **lower lip weakness**, as it runs superficial to the submandibular gland and is vulnerable during dissections in this area. *Main trunk of facial nerve* - Injury to the main trunk would result in **widespread paralysis** of all facial muscles on the affected side, not just isolated lower lip weakness. - The main trunk emerges from the stylomastoid foramen and then enters the parotid gland before branching, so damage here would affect all subsequent branches. *Temporal branch of facial nerve* - This branch innervates muscles responsible for eyebrow movement and forehead wrinkling (e.g., **frontalis muscle**). - Damage to the temporal branch would cause inability to raise the eyebrow and smooth out the forehead, not lower lip weakness. *Parotid duct* - The parotid duct (Stensen's duct) is responsible for transporting saliva from the parotid gland to the oral cavity. - Injury to the parotid duct would lead to complications like **salivary fistula** or **sialocele**, but it does not carry motor innervation to facial muscles and would not cause weakness.
Question 10: Which nerve is most commonly injured during submandibular gland surgery?
- A. Lingual nerve
- B. Marginal mandibular branch of facial nerve (Correct Answer)
- C. Mylohyoid nerve
- D. Hypoglossal nerve
Explanation: ***Marginal mandibular branch of facial nerve*** - The **marginal mandibular nerve** courses superficially over and along the superior border of the submandibular gland, making it the **most vulnerable** structure during surgery - It is at highest risk during elevation of the gland, ligation of the facial vessels, and dissection near the gland's superior border - Injury leads to **weakness or paralysis of the depressor muscles of the lower lip** (depressor anguli oris and depressor labii inferioris), causing an asymmetric smile and difficulty with lip movements - This is the **most common nerve injury** in submandibular gland surgery due to its superficial anatomical position *Incorrect: Lingual nerve* - The **lingual nerve** passes medial to the submandibular duct and deep to the gland - While it can be injured during dissection of the submandibular duct or deeper aspects of the gland, it is **less commonly injured** than the marginal mandibular nerve - Damage results in **loss of taste and general sensation** to the anterior two-thirds of the tongue on the ipsilateral side *Incorrect: Mylohyoid nerve* - The **mylohyoid nerve** travels on the inferior surface of the mylohyoid muscle, generally beneath and protected by this muscle - It supplies the mylohyoid and anterior belly of the digastric muscles - Injury is **uncommon** during routine submandibular gland excision due to its protected anatomical position *Incorrect: Hypoglossal nerve* - The **hypoglossal nerve** lies deep and inferior to the submandibular gland - It supplies motor innervation to the intrinsic and extrinsic muscles of the tongue - It is the **least commonly injured** nerve as it is well-protected by its deep position, unless dissection is carried excessively deep or inferiorly
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