Thyroid Disorders — MCQs
A 6-month-old infant shows delayed social smile, poor head control, and hypotonia. TSH is elevated, and T4 is low. What is the most likely diagnosis?
Which of the following conditions is the most common complication of radioiodine treatment for Graves' disease?
Which of the following forms of thyroid hormone is most readily found in the circulation?
Which of the following is not a feature of hypothyroidism in infancy?
A one-year-old child presents with short stature, lethargy, and constipation. Clinical examination shows a palpable goiter. Laboratory investigations revealed a low T4 and elevated TSH. Which of the following is the most likely diagnosis?
A 30-year-old female complaints of fatigue and is unable to gain weight. On examination, her body felt warm. Which of the following investigation can be helpful in reaching the diagnosis?
Most common cause of Congenital hypothyroidism is
A 5-year-old girl presents with difficulty breathing. On examination of the oral cavity, a 3 cm mass is found in the midline on the posterior aspect of the tongue. The most likely diagnosis is:
Treatment for childhood hypothyroidism is with -
Consider the following disorders : 1. Delayed motor milestones 2. Spastic diplegia 3. Nyctalopia 4. Hearing defects Which of the above disorders occur as part of the spectrum of iodine deficiency disorders ?
Thyroid Disorders Indian Medical PG Practice Questions and MCQs
Question 1: A 6-month-old infant shows delayed social smile, poor head control, and hypotonia. TSH is elevated, and T4 is low. What is the most likely diagnosis?
- A. Down syndrome
- B. Prader-Willi syndrome
- C. Cerebral palsy
- D. Congenital hypothyroidism (Correct Answer)
Explanation: ***Congenital hypothyroidism*** - The combination of **developmental delay** (delayed social smile, poor head control), **hypotonia**, and **abnormal thyroid function tests** (elevated TSH, low T4) is highly suggestive of congenital hypothyroidism. - Early diagnosis and treatment are crucial to prevent **intellectual disability** and severe developmental impairments. *Down syndrome* - While infants with Down syndrome often present with **hypotonia** and developmental delay, the characteristic **facial features** (e.g., epicanthal folds, upward slanting palpebral fissures) and a **normal thyroid profile** would typically differentiate it. - Down syndrome is a **chromosomal disorder** (trisomy 21) not primarily characterized by thyroid dysfunction, although **hypothyroidism** can be a co-occurrence. *Prader-Willi syndrome* - This syndrome is characterized by **severe hypotonia** and feeding difficulties in infancy, followed by childhood-onset **hyperphagia** and obesity. - It is a **genetic disorder** affecting chromosome 15, and while developmental delay and hypotonia are present, routine thyroid function tests are usually normal. *Cerebral palsy* - Cerebral palsy is a group of **motor disorders** caused by non-progressive brain damage that occurs during fetal development or early in life, leading to **abnormal muscle tone**, posture, and movement. - While it can manifest with hypotonia and developmental delay, cerebral palsy is not associated with **elevated TSH and low T4**.
Question 2: Which of the following conditions is the most common complication of radioiodine treatment for Graves' disease?
- A. Hypothyroidism (Correct Answer)
- B. Thyroid cancer
- C. Thyroid storm
- D. Subacute thyroiditis
Explanation: ***Hypothyroidism*** - **Radioiodine (RAI) therapy** destroys overactive thyroid cells, making it highly effective for Graves' disease but often leading to a permanent state of **hypothyroidism** post-treatment. - The goal of RAI is to eliminate the source of excess hormone production, and while effective, it frequently necessitates lifelong **thyroid hormone replacement**. *Thyroid storm* - **Thyroid storm** is a rare, life-threatening complication, usually seen in untreated or undertreated hyperthyroidism or during acute stress, not typically a direct outcome of effective RAI. - While a transient increase in thyroid hormones can occur shortly after RAI, a full-blown thyroid storm is infrequent with proper preparation and management. *Thyroid cancer* - There is no significant evidence to suggest an increased risk of **thyroid cancer** in adults following therapeutic doses of radioiodine for Graves' disease [1]. - The radiation dose is targeted primarily at the thyroid gland, and studies have shown no clear link to increased malignancy [1]. *Subacute thyroiditis* - **Subacute thyroiditis** (also known as de Quervain's thyroiditis) is typically a post-viral inflammatory condition of the thyroid, characterized by pain and tenderness in the thyroid gland [2]. - It does not directly result from radioiodine treatment; however, some patients may experience a transient inflammatory response (radiation thyroiditis) after RAI, which is usually mild and self-limiting, not true subacute thyroiditis.
Question 3: Which of the following forms of thyroid hormone is most readily found in the circulation?
- A. TSH.
- B. Thyroxine (T4). (Correct Answer)
- C. Thyroglobulin.
- D. Tri-iodothyronine (T3).
Explanation: ***Thyroxine (T4)*** - **Thyroxine (T4)** is the primary thyroid hormone secreted by the thyroid gland and is the most abundant form found in the circulation. - Approximately **80%** of the thyroid hormone released is T4, which then undergoes peripheral deiodination to form the more active T3. *TSH* - **TSH (Thyroid-Stimulating Hormone)** is a pituitary hormone that *regulates* thyroid function, not a thyroid hormone produced by the thyroid gland itself. - TSH levels are used to assess thyroid gland activity, but it is not the most abundant thyroid hormone in circulation. *Thyroglobulin* - **Thyroglobulin** is a large glycoprotein produced by thyroid follicular cells that serves as the precursor and storage protein for thyroid hormones *within* the thyroid gland. - While it contains T3 and T4 residues, most thyroglobulin is not released into circulation under normal physiological conditions; elevated levels can indicate thyroid damage or cancer. *Tri-iodothyronine (T3)* - **Tri-iodothyronine (T3)** is the biologically *active* form of thyroid hormone, but it is primarily derived from the peripheral conversion of T4. - Although T3 is more potent than T4, it is present in much lower concentrations in the circulation compared to T4.
Question 4: Which of the following is not a feature of hypothyroidism in infancy?
- A. Umbilical hernia
- B. Constipation
- C. Coarse facies
- D. Premature closure of posterior fontanelle (Correct Answer)
Explanation: ***Premature closure of posterior fontanelle*** - Delayed closure of fontanelles, particularly the **posterior fontanelle**, is a characteristic feature of **congenital hypothyroidism** due to impaired bone maturation. - Therefore, **premature closure** would be inconsistent with a diagnosis of hypothyroidism in infancy. *Coarse facies* - **Coarse facial features** such as a broad nasal bridge, puffy eyelids, and a protuberant tongue are common manifestations of **congenital hypothyroidism** due to the accumulation of glycosaminoglycans. - This is a direct consequence of the metabolic derangements caused by insufficient thyroid hormone. *Umbilical hernia* - An **umbilical hernia** is frequently observed in infants with hypothyroidism, resulting from generalized **hypotonia** and incomplete closure of the umbilical ring. - The reduced muscle tone characteristic of the condition contributes to this physical finding. *Constipation* - **Constipation** is a common gastrointestinal symptom in infants with hypothyroidism, caused by **decreased gut motility** secondary to reduced thyroid hormone levels. - This is a clinical indicator of the systemic metabolic slowing associated with the condition.
Question 5: A one-year-old child presents with short stature, lethargy, and constipation. Clinical examination shows a palpable goiter. Laboratory investigations revealed a low T4 and elevated TSH. Which of the following is the most likely diagnosis?
- A. Thyroid Dyshormonogenesis (Correct Answer)
- B. Central Hypothyroidism
- C. Thyroid Dysgenesis
- D. TSH Receptor Blocking Antibody
Explanation: ***Thyroid Dyshormonogenesis*** - This condition involves a defect in the **synthesis of thyroid hormones**, leading to **hypothyroidism** despite a physically normal or enlarged gland (goiter). - The combination of **goiter (palpable)** with **low T4** and **elevated TSH** in an infant points to the thyroid gland's inability to produce hormones effectively, prompting increased TSH stimulation. *Central Hypothyroidism* - Characterized by **low TSH** (or inappropriately normal TSH) alongside **low T4**, indicating a problem with the pituitary or hypothalamus. - A **goiter would not typically be present** as the thyroid gland is not being excessively stimulated; the child presents with an elevated TSH. *Thyroid Dysgenesis* - This typically presents with an **absent or underdeveloped thyroid gland**, meaning a **goiter would not be palpable**. - While it causes **low T4** and **elevated TSH**, the presence of a palpable goiter rules out dysgenesis. *TSH Receptor Blocking Antibody* - These antibodies block the TSH receptor, leading to **atrophic thyroiditis** and **hypothyroidism**, but typically without a goiter. - The thyroid gland is unable to respond to TSH, but it does not usually cause the gland to grow.
Question 6: A 30-year-old female complaints of fatigue and is unable to gain weight. On examination, her body felt warm. Which of the following investigation can be helpful in reaching the diagnosis?
- A. Elevated TSH with normal thyroid hormone levels
- B. Elevated TSH with low thyroid hormone levels
- C. Normal TSH with abnormal thyroid hormone levels
- D. Suppressed TSH with elevated thyroid hormone levels (Correct Answer)
Explanation: Suppressed TSH with elevated thyroid hormone levels - The patient's symptoms of **fatigue** (despite being warm) and **difficulty gaining weight**, coupled with her body feeling **warm**, are classic signs of **hyperthyroidism**. [1] - In hyperthyroidism, the thyroid gland produces **excessive thyroid hormones (T3 and T4)**, which in turn **suppresses TSH** production from the pituitary gland through negative feedback. [2] *Elevated TSH with normal thyroid hormone levels* - This pattern is characteristic of **subclinical hypothyroidism**, where the thyroid gland is beginning to fail, leading to increased TSH to maintain normal thyroid hormone levels. [3] - The patient's symptoms of feeling warm and difficulty gaining weight are inconsistent with hypothyroidism. [1] *Elevated TSH with low thyroid hormone levels* - This indicates **primary hypothyroidism**, where the thyroid gland is underactive and produces insufficient thyroid hormones, leading to a compensatory rise in TSH. [2] - Hypothyroidism typically presents with **weight gain**, **cold intolerance**, and fatigue, which contradict the patient's presentation. [1] *Normal TSH with abnormal thyroid hormone levels* - This scenario usually suggests **central hypothyroidism** (pituitary or hypothalamic dysfunction affecting TSH production) or **thyroid hormone resistance**. [3] - While possible in some rare cases, it does not fit the typical clinical picture of hyperthyroidism presented by the patient's symptoms.
Question 7: Most common cause of Congenital hypothyroidism is
- A. Iodine deficiency
- B. Thyroid agenesis
- C. Thyroid dysharmonogenesis
- D. Thyroid dysgenesis (Correct Answer)
Explanation: ***Thyroid dysgenesis*** - This is the most prevalent cause of congenital hypothyroidism, accounting for approximately **85% of cases**. - It encompasses a range of developmental abnormalities including **aplasia (agenesis)**, **hypoplasia**, or **ectopia** of the thyroid gland. *Iodine deficiency* - While a common cause of hypothyroidism globally, it is primarily an **environmental cause of acquired hypothyroidism**, not the most frequent cause of *congenital* hypothyroidism in developed countries. - Severe iodine deficiency during pregnancy can lead to **cretinism**, but generally, thyroid dysgenesis is more common for congenital forms. *Thyroid agenesis* - This refers to the **complete absence of the thyroid gland** and is a specific form of thyroid dysgenesis. - While it is a cause of congenital hypothyroidism, the broader category of **thyroid dysgenesis** (which includes agenesis, hypoplasia, and ectopia) is the most common overall cause. *Thyroid dysharmonogenesis* - This term refers to **inborn errors of thyroid hormone synthesis**, also known as **dyshormonogenesis**. - These genetic defects disrupt various steps in thyroid hormone production, but they are collectively less common than thyroid dysgenesis as the cause of congenital hypothyroidism.
Question 8: A 5-year-old girl presents with difficulty breathing. On examination of the oral cavity, a 3 cm mass is found in the midline on the posterior aspect of the tongue. The most likely diagnosis is:
- A. Foreign body stuck to the tongue
- B. Lingual tonsil
- C. Dermoid
- D. Lingual thyroid (Correct Answer)
Explanation: ***Lingual thyroid*** - A lingual thyroid is **ectopic thyroid tissue** located at the base of the tongue, often presenting as a **midline mass**. - Its presence can lead to **obstruction of the airway** or difficulty swallowing, explaining the patient's difficulty breathing. *Foreign body stuck to the tongue* - While a foreign body could cause obstruction, it would typically present with a **sudden onset** and usually has a clear history of ingestion. - A 3 cm mass in the midline is more consistent with a **developmental anomaly** rather than an acutely lodged object. *Lingual tonsil* - The lingual tonsils are normal lymphatic tissue located at the **base of the tongue**; however, they are usually **bilateral and diffuse**, not presenting as a single 3 cm midline mass. - Significant enlargement of a single lingual tonsil to this size causing respiratory distress is **uncommon** without other inflammatory signs. *Dermoid* - A dermoid cyst can appear as a **midline mass** in the oral cavity, but typically it presents as a **soft, doughy, non-transilluminating swelling**. - While it can cause obstructive symptoms if large, a lingual thyroid is a more specific diagnosis for a **vascularized mass** at the base of the tongue in this clinical context.
Question 9: Treatment for childhood hypothyroidism is with -
- A. TSH
- B. Propylthiouracil
- C. Levothyroxine (Correct Answer)
- D. T3
Explanation: ***Correct: Levothyroxine*** - **Levothyroxine** is synthetic **thyroxine (T4)**, the standard hormone replacement therapy for childhood hypothyroidism - It is **well-absorbed orally**, has a **long half-life**, and provides stable thyroid hormone levels - Once administered, it is converted to **T3 (the active form)** in peripheral tissues, ensuring steady thyroid hormone supply - **Preferred in children** for consistent growth and neurodevelopment *Incorrect: TSH* - **TSH (Thyroid-Stimulating Hormone)** is produced by the pituitary gland to stimulate thyroid hormone production - In **primary hypothyroidism**, TSH levels are *elevated* due to lack of negative feedback - TSH is a **diagnostic marker**, not a therapeutic agent for hormone replacement *Incorrect: Propylthiouracil* - **Propylthiouracil** is an **anti-thyroid drug** used to treat **hyperthyroidism** (excessive thyroid hormone) - It works by *inhibiting* thyroid hormone synthesis - Using it in hypothyroidism would **worsen** the condition by further reducing thyroid hormone levels *Incorrect: T3* - **T3 (triiodothyronine)** is the more metabolically active form of thyroid hormone - It has a **shorter half-life** and causes more **fluctuating hormone levels** - **Not preferred** for long-term replacement in children due to difficulty maintaining stable levels - Most levothyroxine (T4) is naturally converted to T3 *in vivo*, providing adequate T3 without direct supplementation
Question 10: Consider the following disorders : 1. Delayed motor milestones 2. Spastic diplegia 3. Nyctalopia 4. Hearing defects Which of the above disorders occur as part of the spectrum of iodine deficiency disorders ?
- A. 2, 3 and 4
- B. 1, 2 and 3
- C. 1 and 3 only
- D. 1, 2 and 4 (Correct Answer)
Explanation: ***1, 2 and 4*** - **Delayed motor milestones** and **spastic diplegia** are hallmark neurological symptoms of **cretinism**, caused by severe congenital iodine deficiency. The spasticity results from pyramidal tract involvement affecting motor development. - **Hearing defects** (sensorineural deafness) are frequently observed in individuals with iodine deficiency disorders due to impaired thyroid hormone synthesis affecting inner ear development during critical developmental periods. *2, 3 and 4* - **Nyctalopia (night blindness)** is primarily associated with **Vitamin A deficiency**, not iodine deficiency. - While spastic diplegia and hearing defects are linked to iodine deficiency, the inclusion of nyctalopia makes this option incorrect. *1, 2 and 3* - This option correctly identifies delayed motor milestones and spastic diplegia as symptoms of iodine deficiency, but **nyctalopia** is an incorrect association with iodine deficiency. - Therefore, the presence of nyctalopia invalidates this choice. *1 and 3 only* - This option correctly includes **delayed motor milestones** but incorrectly includes **nyctalopia** as an iodine deficiency disorder. - It also omits other significant neurological and developmental problems like spastic diplegia and hearing defects that are part of the IDD spectrum.
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