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Thyroid MCQ’s

1. Which is the false statement regarding thyroid embryogenesis?

  • Options:
    • A. Thyroid primordial cells develop from pharyngeal ectoderm
    • B. Migrates caudally posterior to cricoid cartilage
    • C. Foramen caecum embryologic reminder of thyroid origin
    • D. Thyrocytes form thyroid follicles
  • Answer: B. Migrates caudally posterior to cricoid cartilage
  • Explanation:
    • Thyroid primordial cells develop from the pharyngeal ectoderm, forming a medial anlage by gestational days 16-17.
    • The thyroid diverticulum migrates anterior to the cricoid cartilage, not posterior.
    • The foramen cecum is an embryologic reminder of thyroid origin.
    • Thyrocytes are responsible for forming the thyroid follicles.
  • Reference: Clark’s Textbook of Endocrine Surgery, 3rd Edition, Page 3.

2. DiGeorge Syndrome

  • Options:
    • A. Failure of development of parathyroid
    • B. Thymic aplasia
    • C. Cardiac defects and facial malformations
    • D. Microdeletion or rearrangement of long arm of chromosome 22
  • Answer: D. Microdeletion or rearrangement of the long arm of chromosome 22
  • Explanation:
    • DiGeorge Syndrome results from a microdeletion of chromosome 22q11.2 (short arm).
    • It involves failure of development of the parathyroid glands, thymic aplasia, and is accompanied by cardiac and facial defects.
    • The answer reflects that the short arm is involved, not the long arm.
  • Reference: Clark’s Textbook of Endocrine Surgery, 3rd Edition, Page 4.

3. Iodine deficiency is associated with all except?

  • Options:
    • A. Nodular goitre
    • B. Hypothyroidism
    • C. Cretinism
    • D. Papillary carcinoma thyroid
  • Answer: D. Papillary carcinoma thyroid
  • Explanation:
    • Iodine deficiency is associated with nodular goitre, hypothyroidism, and cretinism.
    • Follicular thyroid carcinoma (FTC), not papillary carcinoma thyroid (PTC), is more commonly linked to iodine deficiency.

4. Iodine excess is associated with all the following except?

  • Options:
    • A. Autoimmune Thyroid Disease
    • B. Grave's Disease
    • C. Hashimoto's Thyroiditis
    • D. Follicular Carcinoma Thyroid
  • Answer: D. Follicular Carcinoma Thyroid
  • Explanation:
    • Iodine excess is linked to autoimmune thyroid diseases, such as Grave's disease and Hashimoto's thyroiditis.
    • It is not typically associated with follicular carcinoma thyroid.

5. Transcription factors involved in the development of thyroid gland are all except?

  • Options:
    • A. NKX2-1
    • B. FOXE1
    • C. GATA3
    • D. PAX-8
  • Explanation:
    • Answer: C. GATA3
    • Transcription factors involved in thyroid gland development include NKX2-1, FOXE1, and PAX-8.
    • GATA3 is not involved in thyroid gland development.
    • Mutations in NKX2-1, FOXE1, or PAX-8 are associated with thyroid dysplasia and congenital hypothyroidism.
    • These transcription factors regulate thyroid-specific genes like thyroperoxidase and thyroglobulin.
  • Reference: Clark’s Textbook of Endocrine Surgery, 3rd Edition, Page 3.

Transcription Factors Involved in Thyroid Development

  1. Key Transcription Factors:
    • NKX2-1: Previously known as thyroid transcription factor 1 (TTF-1).
    • FOXE1: Formerly referred to as TTF-2.
    • PAX8: A paired homeodomain factor.
  2. Roles in Thyroid Development:
    • These transcription factors bind to specific regulatory elements within the promoters of thyroid-specific genes, such as:
      • Thyroperoxidase
      • Thyroglobulin
    • These factors are expressed during the descent of the thyroid primordium from its pharyngeal origin.
  3. Mutations and Associated Conditions:
    • NKX2-1: Associated with thyroid dysplasia, congenital hypothyroidism, pulmonary disease, and choreoathetosis.
    • FOXE1: Associated with cleft palate.
    • PAX8: Linked to renal hemiagenesis.
  4. Other Homeobox Transcription Factors:
    • NKX2-5: Rarely associated with congenital hypothyroidism.
    • Other factors such as Hhex, Hoxa3, and Pax3 are also relevant to thyroid development, particularly in mouse models.

6. Hypoparathyroidism is associated with mutations in all except?

A. GATA3

B. TBCE

C. NKX2-1

D. GCM2

Explanation:

  • Answer: C (NKX2-1)
  • Reference: Clark's Textbook of Endocrine Surgery, 3rd Edition, Page 3
  • GATA3: Associated with HDR syndrome, which includes hypoparathyroidism, sensorineural deafness, and renal aplasia.
  • TBCE: [Tubulin-specific chaperone E] Involved in hypoparathyroidism-retardation-dysmorphism syndrome.
  • GCM2: Linked to familial isolated hypoparathyroidism.
  • NKX2-1: Primarily related to thyroid development and not typically associated with hypoparathyroidism, making it the correct answer as the exception.

7. Ratio of levels of T3 and T4 in stored thyroglobulin is

A. 1:13

B. 1:10

C. 1:20

D. 1:18

Explanation:

  • Answer: A (1:13)

The ratio of T3 to T4 in stored thyroglobulin is approximately 1:13, indicating a much higher concentration of T4 compared to T3 in stored thyroglobulin.

8. Thyroid hormone receptors. All are true except?

A. Steroid hormone receptor superfamily

B. 2 TR genes, α and β

C. Alpha and Beta are located on chromosomes 17 and 4 respectively

D. Differential splicing yields 4 different isoforms TRα1 and 2, TRβ1 and 2

Explanation:

  • Answer: C (Alpha and Beta are located on chromosomes 17 and 4 respectively)
  • Correct Information: Chromosome 17 and Chromosome 3
  • Steroid hormone receptor superfamily: Thyroid hormone receptors belong to this superfamily.
  • 2 TR genes, α and β: There are two primary genes for thyroid hormone receptors—TRα and TRβ.
  • Location: TRα is located on chromosome 17, while TRβ is located on chromosome 3 (not 4, making this the false statement).
  • Differential splicing: This process results in the four isoforms—TRα1, TRα2, TRβ1, and TRβ2.

9. TSH has Alpha and Beta subunit, and the α-subunit is common to all the following except?

A. Follicle-stimulating hormone

B. Luteinizing hormone

C. Human chorionic gonadotropin

D. Oxytocin

Explanation:

  • Answer: D (Oxytocin)

TSH, FSH, LH, and hCG share the same α-subunit, while their β-subunits provide specificity for their function. Oxytocin does not share this α-subunit, as it is a completely different hormone.

10. All are true regarding Calcitonin except?

A. Secreted by parafollicular C cells

B. 32 amino acid polypeptide with disulfide ring

C. Downregulated by pentagastrin infusion, alcohol

D. Acts principally by inhibition of bone resorption

Explanation:

  • Answer: C (Downregulated by pentagastrin infusion, alcohol)

Calcitonin secretion is actually stimulated by calcium infusion, pentagastrin, and alcohol, not downregulated. The hormone is secreted by C cells, is a 32 amino acid polypeptide, and primarily functions to inhibit bone resorption, helping to lower serum calcium levels.

11. All are true about Calcitonin except?

A. Inhibits osteoclast action

B. In physiological situations, does not cause lowering of calcium levels

C. In medullary carcinoma of the thyroid (MCT), calcitonin levels are 1000x normal

D. Causes severe hypocalcemia in MCT

Explanation:

  • Answer: D (Causes severe hypocalcemia in MCT)

Even though calcitonin levels are extremely high in MCT, hypocalcemia is not observed. Patients with total thyroidectomy (no C cells left) maintain normal calcium metabolism, implying that calcitonin does not play a crucial role in maintaining calcium levels physiologically.

12. Identify the incorrect statement

A. Thyroid gland weighs an average of 17g, wrapped around upper tracheal rings and larynx

B. Relations: carotid sheath posteriorly, SCM, sternohyoid, and sternothyroid laterally and anteriorly

C. If the strap muscles are to be divided, it must be done high at cricothyroid level

D. Sectioning of strap muscles has gross functional consequences

Explanation:

  • Answer: D (Sectioning of strap muscles has gross functional consequences)

The strap muscles (sternohyoid, sternothyroid) can be divided without significant clinical functional consequences. If they are divided, it should be done high near the cricoid to preserve their innervation.

13. Identify the false statement

A. Color of the parathyroid gland depends on adipocyte content and vascularization

B. Light brown or coffee-colored when very fatty

C. Darker or reddish brown when more cellular or vascular

D. Hard and do not retain original shape during dissection

Explanation:

  • Answer: D (Hard and do not retain original shape during dissection)

Parathyroid glands are soft and supple, and they do retain their shape during dissection. They can become flattened by adjacent structures but will return to their original shape once separated.

14. Venous drainage of parathyroid gland, all are true except?

A. By capsular network of thyroid

B. Venous pedicles of thyroid body

C. None of the above

D. Combination of A and B

  • Answer: C (None of the above)

Explanation:

  • The venous drainage of the parathyroid glands occurs via three main routes:
    1. Capsular network of the thyroid
    2. Venous pedicles of the thyroid body
    3. Combination of both capsular network and venous pedicles
  • When a thyroid lobectomy is performed, it can render the ipsilateral parathyroid glands ischemic due to disruption of their venous drainage.

15. Superior parathyroid is supplied by all except?

A. Inferior thyroid artery

B. Posterior branch of superior thyroid artery

C. Anterior branch of superior thyroid artery

D. Posterior marginal arch of Evans

  • Answer: C (Anterior branch of superior thyroid artery)

Explanation:

  • The superior parathyroid gland receives its blood supply from:
    • Inferior thyroid artery
    • Posterior branch of superior thyroid artery
    • Posterior marginal arch of Evans
  • The anterior branch of the superior thyroid artery does not supply the superior parathyroid gland.

16. Grading system of endemic goitres, all are false except:

A. Grade 1: No palpable or visible goitre

B. Grade 2: Palpable but not visible in neutral neck position

C. Grade 3: Visible and palpable in neutral neck position

D. Has 3 grades

  • Answer: D (Has 3 grades)

Explanation:

  • The grading system for endemic goiters is as follows:
    • Grade 0: No palpable or visible goiter
    • Grade 1: Palpable but not visible goiter in a neutral neck position; moves upward when swallowing
    • Grade 2: Visible goiter in a neutral neck position and palpable on examination
    • Grade 3: Visible and palpable in a neutral neck position; more prominent

17. Iodine deficiency disorders (IDD), all are true except?

A. Done through supplementation and food fortification

B. Prevention of endemic goiters

C. Iodization of salt does affect color, taste, or odor

D. Public health education of people helps in the long term

  • Answer: C (Iodization of salt does affect color, taste, or odor)

Explanation:

  • Iodization of salt does not affect its color, taste, or odor.
  • Public health initiatives for iodine deficiency prevention involve:
    • Supplementation and food fortification
    • Education of the public to raise awareness
    • Iodine deficiency prevention helps reduce the prevalence of endemic goiters.

18. Clinically relevant size reduction following medical therapy in diffuse endemic goitre refers to:

A. <25% reduction in size

B. >25% reduction in size

C. <50% reduction in size

D. >50% reduction in size

  • Answer: D (>50% reduction in size)

Explanation:

  • LT4 (levothyroxine) therapy is effective in reducing the size of diffuse goiters.
  • Clinically significant size reduction is considered a >50% decrease in goiter size, and this is more common in diffuse goiters than in nodular goiters.

19. rhTSH is used in:

A. Facilitate RAI therapy

B. Can double thyroid RAI uptake

C. Approved only for treatment of thyroid malignancy

D. All of the above

  • Answer: D (All of the above)

Explanation:

  • Recombinant human TSH (rhTSH) is used to:
    • Facilitate RAI therapy (radioactive iodine) by increasing the uptake of RAI.
    • It can double thyroid RAI uptake.
    • Currently, rhTSH is approved for treating thyroid malignancies but is being evaluated in off-label studies for other thyroid conditions such as goiters.

20. Postoperative permanent hypoparathyroidism:

A. <3%

B. <1%

C. >1%

D. >3%

  • Answer: A (<3%)

Explanation:

  • Permanent hypoparathyroidism is a rare complication of thyroid surgery.
  • The acceptable rate of permanent hypoparathyroidism post-surgery is reported to be between 1% and 2% in specialized thyroid surgery centers around the world.
  • Therefore, the rate of <3% is considered an acceptable outcome in most thyroid surgeries.

21. Most common location of thyroglossal duct cyst

A. Infrahyoid

B. Suprahyoid

C. Suprasternal

D. Lingual

  • Answer: A (Infrahyoid)

Explanation:

  • The most common location of a thyroglossal duct cyst is infrahyoid or thyrohyoid, found in 60-80% of cases. It typically lies close to or just inferior to the body of the hyoid bone, between the hyoid bone and the thyroid cartilage.
  • Other less common locations include:
    • Suprahyoid (25%)
    • Suprasternal (7-13%)
    • Lingual (1-2%)
  • Rare atypical locations include intrahyoid, intrathyroid, intralaryngeal, and mediastinal.

22. Sistrunk's operation may injure the following nerves except?

A. Superior laryngeal nerve

B. Lingual nerve

C. Hypoglossal nerve

D. Recurrent laryngeal nerve

  • Answer: D (Recurrent laryngeal nerve)

Explanation:

  • In Sistrunk’s operation, care must be taken to avoid injury to certain nerves while performing the central hyoidectomy. The operation requires removal of a generous cuff of tissue around the hyoid bone, and staying in the midline is important to avoid injury.
  • Nerves at risk include:
    • Lingual nerve
    • Superior laryngeal nerve
    • Hypoglossal nerve
  • Recurrent laryngeal nerve is not at risk in this procedure.

23. AUS or FUS refers to

A. Bethesda 2

B. Bethesda 3

C. Bethesda 4

D. Bethesda 1

  • Answer: B (Bethesda 3)

Explanation:

  • Atypia of Undetermined Significance (AUS) or Follicular Lesion of Undetermined Significance (FUS) corresponds to Bethesda 3 in the Bethesda System for Reporting Thyroid Cytopathology.
  • The Bethesda classification system includes:
    • 1: Nondiagnostic
    • 2: Benign
    • 3: AUS/FUS
    • 4: Suspicious for follicular or Hürthle cell neoplasm
    • 5: Suspicious for malignancy
    • 6: Malignant

24. Side effects of Radio iodine therapy include all except?

A. Hypothyroidism

B. Induction of Grave's disease

C. Permanent thyrotoxicosis

D. Radiation thyroiditis

  • Answer: C (Permanent thyrotoxicosis)

Explanation:

  • Side effects of radioiodine therapy include:
    • Hypothyroidism (20-30% at 5 years post-treatment)
    • Radiation thyroiditis, which is usually mild but can cause acute thyroid swelling in patients with large substernal goiters.
    • Induction of Graves' disease in about 5% of patients due to release of antigens that stimulate an autoimmune response.
    • Temporary thyrotoxicosis, which can be managed with antithyroid drugs and/or adrenergic blocking agents before and after 131I administration.
  • Permanent thyrotoxicosis is not a side effect of radioiodine therapy.

25. Hartley-Dunhill operation

A. Total thyroidectomy

B. Sub-total Lobectomy on both sides

C. Total lobectomy on one side and sub-total lobectomy of the other

D. Isthmusectomy

  • Answer: C (Total lobectomy on one side and sub-total lobectomy of the other)

Explanation:

  • The Hartley-Dunhill operation involves a total lobectomy on one side and a subtotal lobectomy on the other side, leaving a 4-5 g remnant of thyroid tissue posteriorly.
  • This operation is preferred as it minimizes the extent of surgery if reoperation is necessary in case of recurrence.

26. de Quervain's thyroiditis, all are true except:

A. Granulomatous thyroiditis

B. Subacute granulomatous thyroiditis

C. Pseudogranulomatous thyroiditis

D. Surgery is the mainstay of treatment

  • Answer: D (Surgery is the mainstay of treatment)

Explanation:

  • de Quervain's thyroiditis is also known as:
    • Granulomatous thyroiditis
    • Subacute granulomatous thyroiditis
    • Pseudogranulomatous thyroiditis
  • It is the most common cause of a painful thyroid gland, first described by de Quervain in 1904.
  • Thyroidectomy (surgery) is not the mainstay of treatment; it is reserved only for rare cases where the condition does not respond to medical management.

27. Chronic autoimmune thyroiditis, all are true except:

A. Has two forms: atrophic and goitrous

B. Hashimoto's thyroiditis is the most common inflammatory disease of the thyroid

C. Is mostly in the atrophic form

D. Struma lymphomatosa refers to transformation of thyroid tissue to lymphoid tissue

  • Answer: C (Is mostly in the atrophic form)

Explanation:

  • Chronic autoimmune thyroiditis has two forms:
    • Atrophic form
    • Goitrous form (Hashimoto's thyroiditis)
  • Hashimoto's thyroiditis is the most common inflammatory disease of the thyroid and was first described as struma lymphomatosa in 1912, which refers to the transformation of thyroid tissue into lymphoid tissue.
  • The goitrous form is more common than the atrophic form.

28. Characteristics in Hashimoto's thyroiditis, all are true except:

A. Lined by Hürthle or Askanazy cells

B. Abundant eosinophilic and granular cytoplasm

C. Fibrosis if >30% is considered the fibrous variant

D. Fibrosis if >50% is considered the fibrous variant

  • Answer: D (Fibrosis if >50% is considered the fibrous variant)

Explanation:

  • Hashimoto's thyroiditis is characterized by follicles lined by Hürthle or Askanazy cells, with abundant eosinophilic and granular cytoplasm.
  • Fibrosis is considered the fibrous variant if it involves ≥30% of the gland. If fibrosis is extensive, the remaining thyroid tissue shows lymphocytic change.

29. Incidence of hashitoxicosis:

A. 1%

B. 3%

C. 5%

D. 10%

  • Answer: C (5%)

Explanation:

  • Approximately 20% of patients with chronic autoimmune thyroiditis present with hypothyroidism, and 5% present with hyperthyroidism (hashitoxicosis).

30. Higher incidence of baseline chronic autoimmune thyroid disease is seen in all except:

A. MEN 2

B. POEMS syndrome

C. Addison's disease

D. Turcot's syndrome

  • Answer: D (Turcot's syndrome)

Explanation:

  • A higher incidence of chronic autoimmune thyroid disease is seen in patients with:
    • MEN 2 (Multiple Endocrine Neoplasia type 2)
    • POEMS syndrome (Polyneuropathy, Organomegaly, Endocrinopathy, M protein, and Skin changes)
    • Addison's disease
    • Down syndrome and Turner syndrome
  • Turcot's syndrome is not associated with a higher incidence of autoimmune thyroid disease.

31. All are true regarding Riedel's thyroiditis except:

A. Progressive painless hard anterior neck mass

B. "Woody" thyroid gland

C. FNAC diagnostic

D. Surgery is the mainstay of treatment

  • Answer: C (FNAC diagnostic)

Explanation:

  • Riedel's thyroiditis presents as a progressive, painless, hard anterior neck mass, often described as a "woody" thyroid gland.
  • The diagnosis cannot be confirmed with FNAC (Fine Needle Aspiration Cytology) as it is inadequate due to the fibrous nature of the gland.
  • Surgery is considered a treatment option when there are compressive symptoms, but the diagnosis is confirmed by open thyroid biopsy to rule out malignancy.

32. Causes of primary hypothyroidism include:

A. Iodine deficiency

B. Total thyroidectomy

C. Radioactive iodine

D. All of the above

  • Answer: D (All of the above)

Explanation:

  • Primary hypothyroidism can result from several causes, including:
    • Iodine deficiency
    • Total thyroidectomy
    • Radioactive iodine treatment
  • Other causes include chronic autoimmune thyroiditis (e.g., Hashimoto's), subacute lymphocytic/postpartum thyroiditis, and Riedel's thyroiditis.

33. Graves' disease, all are true except:

A. Smoking is the strongest modifiable risk factor

B. Most common cause of hyperthyroidism in the US

C. Ophthalmopathy and dermopathy may occur with periods of remission

D. Extrathyroidal manifestations are more common in toxic multinodular goiter

  • Answer: D (Extrathyroidal manifestations are more common in toxic MNG)

Explanation:

  • Graves' disease is the most common cause of hyperthyroidism in the US.
  • Smoking is a major modifiable risk factor for the development and exacerbation of Graves' disease.
  • It is characterized by extrathyroidal manifestations such as ophthalmopathy and dermopathy (e.g., pretibial myxedema), which can occur with periods of remission.
  • These extrathyroidal manifestations are not common in toxic multinodular goiter (MNG), which lacks the immunologic features seen in Graves' disease.

34. Absolute indications for surgery in Graves' disease are all except:

A. Graves with suspected malignant nodule

B. Pregnant females not controlled with antithyroid drugs

C. Children

D. Poor compliance to medical therapy

  • Answer: D (Poor compliance to medical therapy)

Explanation:

  • Absolute indications for surgery in Graves' disease include:
    • Graves' disease with suspected malignant nodule
    • Pregnant females not controlled with antithyroid medications
    • Children with Graves' disease
    • Local compressive symptoms and recurrence after antithyroid drug treatment.
  • Poor compliance to medical therapy is not considered an absolute indication for surgery, though it may influence treatment decisions.

35. Plummer's disease, all are true except:

A. Toxic MNG or solitary toxic nodule

B. As common as Graves' disease

C. Extrathyroidal manifestations absent

D. Thyroid antibodies absent

  • Answer: B (As common as Graves' disease)

Explanation:

  • Plummer's disease refers to toxic multinodular goiter (MNG) or solitary toxic nodule.
  • It is not as common as Graves' disease, especially in iodine-sufficient areas, where it accounts for less than 5% of thyrotoxicosis cases.
  • Extrathyroidal manifestations and thyroid antibodies are typically absent in Plummer's disease, distinguishing it from Graves' disease.

36. Inherited syndromes with thyroid cancer are all except?

Question:

Which of the following inherited syndromes is not associated with thyroid cancer?

A. FAP

B. Gardner’s Syndrome

C. MEN1

D. PTEN Hamartoma tumor syndrome

Answer: C (MEN1)

Explanation:

  • FAP (Familial adenomatous polyposis) is associated with papillary thyroid cancer (PTC), particularly the cribriform morular variant.
  • Gardner's Syndrome is a variant of FAP and is associated with an increased risk of PTC > FTC (follicular thyroid cancer).
  • PTEN Hamartoma tumor syndrome is associated with follicular thyroid cancer (FTC).
  • MEN1 (Multiple Endocrine Neoplasia Type 1) is not associated with thyroid cancer, unlike MEN2A and MEN2B, which are linked to medullary thyroid cancer (MTC).
  • Other syndromes linked to thyroid cancer include Carney complex, Cowden's syndrome (FTC), Werner's syndrome, and Familial medullary thyroid cancer.

Reference: Clark's Textbook of Endocrine Surgery, 3rd Edition, Page 121

37. USG features of suspicion of malignancy in a thyroid nodule

Question:

Which of the following is not a feature of malignancy in a thyroid nodule on ultrasonography?

A. Absence of hypoechoic surrounding halo

B. Irregular borders

C. Hypovascularity

D. Microcalcifications

Answer: C (Hypovascularity)

Explanation:

Ultrasonography (USG) identifies suspicious features that may indicate malignancy in a thyroid nodule:

  • Hypoechogenicity
  • Irregular borders
  • Absence of a hypoechoic surrounding halo
  • Hypervascularity (not hypovascularity)
  • Microcalcifications

These features suggest a higher risk of malignancy, and nodules exhibiting these characteristics warrant further investigation.

Reference: Clark's Textbook of Endocrine Surgery, 3rd Edition, Page 123

38. Risk of malignancy in Bethesda Category 4 FNA

Question:

What is the risk of malignancy in a fine-needle aspiration (FNA) biopsy categorized as Bethesda 4?

A. 1-4%

B. 0-3%

C. 5-15%

D. 15-30%

Answer: D (15-30%)

Explanation:

Bethesda 4 (Follicular Neoplasm or Suspicious for Follicular Neoplasm) represents a risk of malignancy of 15-30%. In such cases, thyroid lobectomy is recommended for low-risk patients with a single asymptomatic nodule and a functional thyroid, to confirm the diagnosis and potentially remove the malignancy.

Reference: Clark's Textbook of Endocrine Surgery, 3rd Edition, Page 125

39. The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) - All are true except?

Question:

Which of the following statements about the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) is incorrect?

A. 6 tiers of risk

B. 4 - Follicular neoplasm or Hürthle cell neoplasm

C. 2 - Benign

D. 6 - Suspicious for malignancy

Answer: D (6 - Suspicious for malignancy)

Explanation:

TBSRTC has six distinct risk categories:

  1. Nondiagnostic/Unsatisfactory
  2. Benign
  3. Atypia of undetermined significance (AUS) or Follicular lesion of undetermined significance (FLUS)
  4. Suspicious for Follicular or Hürthle cell neoplasm
  5. Suspicious for malignancy
  6. Malignant

The incorrect statement is that Tier 6 represents 'Suspicious for malignancy'; in fact, it represents 'Malignant'.

Reference: Clark's Textbook of Endocrine Surgery, 3rd Edition, Page 125

Question:

In which Bethesda category is surgery the primary recommended management?

A. Bethesda 2

B. Bethesda 4

C. Bethesda 1

D. Bethesda 3

Answer: B (Bethesda 4)

Explanation:

Bethesda Category 4 (Follicular Neoplasm or Suspicious for Follicular Neoplasm) represents a risk of malignancy of 15-30%, prompting a recommendation for thyroid lobectomy in patients with low-risk profiles and a single asymptomatic nodule. Surgery helps confirm the diagnosis and treat any potential malignancy.

Reference: Clark's Textbook of Endocrine Surgery, 3rd Edition, Page 125

New Set

41. Identify the incorrect statement regarding the thyroid gland

Question:

Which of the following is an incorrect statement about the thyroid gland?

A. Contains 2 separate physiologic endocrine systems

B. One responsible for production of T3 and T4

C. Other responsible for production of calcitonin

D. None of the above

Answer: D (None of the above)

Explanation:

  • The thyroid gland consists of two distinct endocrine systems:
    1. One responsible for the production of thyroid hormones T3 (triiodothyronine) and T4 (thyroxine).
    2. The other responsible for the production of calcitonin, a hormone involved in calcium metabolism.

These statements are accurate, and hence, there is no incorrect option.

Reference: Clark's Textbook of Endocrine Surgery, 3rd Edition, Page 3

42. Identify the correct statement regarding the thyroid gland

Question:

Which of the following statements about the thyroid gland is correct?

A. Functional unit is the thyroid follicle

B. Size of the follicle varies from 100 to 300 microns

C. Primary function is to make and store thyroid hormones

D. All of the above

Answer: D (All of the above)

Explanation:

  • The thyroid follicle is the functional unit responsible for the production of thyroid hormones.
  • The average size of the follicle varies from 100 to 300 microns, with each follicle surrounded by capillaries.
  • The primary function of these follicles is to synthesize and store thyroid hormones, which are eventually released into the bloodstream.
  • Calcitonin, on the other hand, is produced by C cells (parafollicular cells) of neural crest origin located within the thyroid.

Reference: Clark's Textbook of Endocrine Surgery

43. The thyroid diverticulum forms from a thickening in

Question:

From where does the thyroid diverticulum form?

A. Midline of the anterior pharyngeal floor

B. Midline of the posterior pharyngeal floor

C. Midline of the lateral pharyngeal floor

D. All of the above

Answer: A (Midline of the anterior pharyngeal floor)

Explanation:

The thyroid diverticulum originates from a thickening in the midline of the anterior pharyngeal floor, which later gives rise to the thyroid gland during embryonic development.

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44. Identify the incorrect statement regarding thyroid development

Question:

Which of the following statements about thyroid development is incorrect?

A. Thyroid diverticulum migrates caudally anterior to the cricoid cartilage

B. Infiltrated by cells from ultimobranchial bodies

C. Superior parathyroids seen posterolateral to the thyroid

D. Inferior parathyroids seen anteromedial to the thyroid

Answer: D (Inferior parathyroids seen anteromedial to the thyroid)

Explanation:

  • The thyroid diverticulum migrates caudally, anterior to the cricoid cartilage.
  • The ultimobranchial bodies contribute C cells to the thyroid.
  • The superior parathyroids are located posterolateral to the thyroid gland, but the inferior parathyroids are actually located inferolateral, not anteromedial, making option D incorrect.

Reference: Clark's Textbook of Endocrine Surgery, 3rd Edition, Page 4

45. Uptake of iodide into the follicular cells is by

Question:

How is iodide transported into the follicular cells?

A. Passive transport

B. Diffusion

C. Active transport

D. None of the above

Answer: C (Active transport)

Explanation:

Iodide is actively transported into thyroid follicular cells through a sodium/iodide symporter located on the basolateral membrane of these cells. This process is crucial for the synthesis of thyroid hormones.

46. True regarding thyroglobulin are all except

Question:

Which of the following statements about thyroglobulin is incorrect?

A. Synthesis occurs exclusively in the thyroid gland

B. Small quantities can be detected in normal individuals

C. Defect in synthesis causes moderate to severe hypothyroidism with raised blood levels

D. Multiple vesicles containing thyroglobulin are incorporated into follicular cells by endocytosis

Answer: C (Defect in synthesis causes moderate to severe hypothyroidism with raised blood levels)

Explanation:

  • Thyroglobulin is synthesized exclusively in the thyroid gland, where it is stored in the colloid of the thyroid follicles.
  • Small amounts of thyroglobulin can be detected in the blood of normal individuals.
  • However, defects in thyroglobulin synthesis typically result in moderate to severe hypothyroidism with low blood levels of thyroglobulin, not raised levels.
  • Multiple vesicles containing thyroglobulin are indeed incorporated into the follicular cells by endocytosis during the hormone release process.

47. True regarding Pendred's Syndrome

Question:

Which of the following statements about Pendred's Syndrome is true?

A. A partial organification defect of thyroglobulin

B. Goitre

C. Sensorineural deafness

D. All of the above

Answer: D (All of the above)

Explanation:

Pendred's Syndrome is characterized by:

  • A partial organification defect of thyroglobulin.
  • The presence of goitre, with or without overt hypothyroidism.
  • Sensorineural deafness due to mutations in the PDS gene that encodes the pendrin protein.

48. True regarding Pendred's Syndrome A/E

Question:

Which of the following is not true about Pendred's Syndrome?

A. Goitre with or without overt hypothyroidism

B. Sensorineural deafness

C. Mutation in a putative sulfate transporter gene

D. None of the above

Answer: D (None of the above)

Explanation:

All the given statements are true regarding Pendred's Syndrome:

  • Goitre may occur with or without overt hypothyroidism.
  • Sensorineural deafness is a hallmark of the syndrome.
  • The condition is linked to mutations in a putative sulfate transporter gene (PDS).

49. Identify the correct statement regarding thyroid hormones

Question:

Which of the following statements about thyroid hormones is correct?

A. 99% of circulating thyroid hormones are free

B. 99% are bound to serum proteins

C. Transthyretin transports most of the thyroid hormone

D. Albumin-bound is the main storage form

Answer: B (99% are bound to serum proteins)

Explanation:

  • More than 99% of thyroid hormones are bound to serum proteins, primarily thyroxine-binding globulin (TBG), with smaller amounts bound to transthyretin and albumin.
  • Only a small fraction of thyroid hormones remains in the free form, which is biologically active.

50. Circulating thyroid hormones are bound to

Question:

Which proteins bind circulating thyroid hormones?

A. Thyroxine-binding globulin

B. Transthyretin

C. Albumin

D. All of the above

Answer: D (All of the above)

Explanation:

Thyroid hormones in circulation are predominantly bound to:

  • Thyroxine-binding globulin (TBG), which carries the majority of thyroid hormones.
  • Transthyretin (also known as prealbumin).
  • Albumin, which binds a smaller fraction of thyroid hormones.

51. Type II 5'deiodinase is seen in all except?

Question:

In which of the following tissues is Type II 5'deiodinase (5'DII) not present?

A. CNS

B. Pituitary

C. Placenta

D. Kidney

Answer: D (Kidney)

Explanation:

  • Type I deiodinase (5'DI) is predominantly found in the liver, kidney, and thyroid and is responsible for converting T4 to T3 in peripheral tissues.
  • Type II deiodinase (5'DII) is present in the central nervous system (CNS), pituitary, placenta, brown adipose tissue, cardiac and skeletal muscle, and thyroid. It plays a key role in maintaining local T3 levels in these tissues.
  • Type III deiodinase (5'DIII), which inactivates thyroid hormones, is found in the placenta and CNS, where it converts T4 to reverse T3 (rT3).

The kidney is not a site for Type II 5'deiodinase, making option D correct.

52. Critical subtype receptor involved in the negative feedback effects of T3

Question:

Which of the following thyroid hormone receptors is involved in the negative feedback regulation of T3?

A. TRalpha1

B. TRalpha2

C. TRbeta1

D. TRbeta2

Answer: D (TRbeta2)

Explanation:

  • Thyroid hormone receptors (TRs) are encoded by two genes, TRα and TRβ, which give rise to different isoforms such as TRalpha1, TRalpha2, TRbeta1, and TRbeta2.
  • TRalpha1 is predominantly expressed in tissues like the myocardium, skeletal muscle, and fat.
  • TRbeta1 is found in the pituitary and liver.
  • TRbeta2 is specifically expressed in the hypothalamus and pituitary, where it plays a critical role in mediating the negative feedback effects of T3 on thyroid-stimulating hormone (TSH) secretion, making it the primary receptor involved in this feedback loop.

Reference: The TRbeta2 receptor is particularly important in the negative regulation of TSH production in response to T3 levels, ensuring proper hormonal balance.

15. Identify the incorrect statement regarding Thyroxine Receptors

Question:

Which of the following statements about thyroxine receptors is incorrect?

A. TRalpha derived from Chr 17

B. TRbeta derived from Chr 3

C. TRalpha1 and 2 isoforms differ via their aminotermini

D. TRbeta1 and 2 isoforms differ via their aminotermini

Answer: C (TRalpha1 and 2 isoforms differ via their aminotermini)

Explanation:

  • TRalpha is indeed derived from chromosome 17, and TRbeta is derived from chromosome 3, making options A and B correct.
  • TRalpha1 and TRalpha2 differ in their carboxy termini, not the aminotermini, making option C incorrect.
  • TRbeta1 and TRbeta2 differ in their aminotermini, making option D correct.

Reference: The figure from Lazar illustrates the differential splicing of the primary messenger RNA that results in these isoform variations.

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17. The alpha subunit of TSH is common to

Question:

The alpha subunit of TSH is common to which of the following hormones?

A. FSH

B. LH

C. hCG

D. All of the above

Answer: D (All of the above)

Explanation:

  • The alpha subunit of TSH (Thyroid-Stimulating Hormone) is structurally identical to the alpha subunits of FSH (Follicle-Stimulating Hormone), LH (Luteinizing Hormone), and hCG (Human Chorionic Gonadotropin).
  • The beta subunits of these hormones differ, providing hormone-specific biological activity.

18. External factors that can affect thyroid regulation include

Question:

Which of the following external factors can affect thyroid regulation?

A. Nonthyroidal illness

B. Starvation

C. Temperature changes

D. All of the above

Answer: D (All of the above)

Explanation:

Several external factors can influence thyroid regulation:

  • Nonthyroidal illness: Illnesses not directly related to the thyroid can affect thyroid hormone levels.
  • Starvation: Prolonged fasting or malnutrition leads to reduced levels of thyroid hormones, especially T3.
  • Temperature changes: Exposure to extreme temperatures, particularly cold, can affect thyroid function by altering metabolic demands.

These factors can lead to altered thyroid hormone levels without directly affecting the thyroid gland itself.

19. Sick euthyroid syndrome refers to

Question:

Sick euthyroid syndrome refers to which of the following?

A. Reduced levels of peripheral thyroid hormone levels

B. Absence of compensatory rise in TSH

C. Both of the above

D. None of the above

Answer: C (Both of the above)

Explanation:

Sick euthyroid syndrome occurs during severe illness or stress and is characterized by:

  • Reduced peripheral levels of thyroid hormones (T3 and T4).
  • No compensatory rise in TSH, despite low thyroid hormone levels. This distinguishes it from primary hypothyroidism, where TSH would be elevated in response to low thyroid hormone levels.

This syndrome is also called non-thyroidal illness syndrome and is a common finding in critically ill patients.

20. Wolff-Chaikoff effect

Question:

What is the Wolff-Chaikoff effect?

A. Is a thyroid hormone autoregulatory mechanism

B. Excessive dietary iodide causes increase in organification initially

C. Later decreased organification

D. All of the above

Answer: D (All of the above)

Explanation:

The Wolff-Chaikoff effect is a thyroid autoregulatory mechanism that occurs when there is an excess of dietary iodide:

  • Initially, the thyroid gland increases iodide organification (the process by which iodide is incorporated into thyroid hormones).
  • However, continued excessive iodide intake leads to a decrease in organification and a subsequent reduction in thyroid hormone synthesis.
  • This effect helps prevent iodide-induced hyperthyroidism by temporarily inhibiting hormone production when iodine levels are excessive.

This mechanism illustrates how the thyroid can control its own hormone production based on iodine availability.