Thyroid Gland in Human Anatomy MCQ Questions and Answers

1. The thyroid gland develops from which embryological structure?
A) Third pharyngeal pouch
B) Fourth pharyngeal pouch
C) Endodermal thickening at the foramen cecum
D) Neural crest cells
Answer: C) Endodermal thickening at the foramen cecum

2. The isthmus of the thyroid gland typically lies opposite which tracheal rings?
A) 1st and 2nd
B) 2nd and 3rd
C) 3rd and 4th
D) 4th and 5th
Answer: B) 2nd and 3rd

3. Which artery is most commonly injured during ligation near the superior pole of the thyroid gland?
A) Inferior thyroid artery
B) Thyroidea ima artery
C) Superior thyroid artery
D) External carotid artery
Answer: C) Superior thyroid artery

4. The recurrent laryngeal nerve is closely related to which structure near the thyroid?
A) Superior thyroid artery
B) Thyroidea ima vein
C) Inferior thyroid artery
D) Internal jugular vein
Answer: C) Inferior thyroid artery

5. Which nerve is at risk during ligation of the superior thyroid artery?
A) Recurrent laryngeal nerve
B) External branch of superior laryngeal nerve
C) Hypoglossal nerve
D) Internal laryngeal nerve
Answer: B) External branch of superior laryngeal nerve

6. The pyramidal lobe of the thyroid gland, when present, extends from which structure?
A) Inferior thyroid vein
B) Isthmus
C) Lateral lobe
D) Tracheal cartilage
Answer: B) Isthmus

7. Which of the following is derived from ultimobranchial body?
A) Parafollicular cells (C cells)
B) Follicular cells
C) Thyroglobulin
D) Colloid
Answer: A) Parafollicular cells (C cells)

8. Which of the following hormones is secreted by parafollicular cells?
A) Thyroxine (T4)
B) Triiodothyronine (T3)
C) Calcitonin
D) Thyroglobulin
Answer: C) Calcitonin

9. Which enzyme catalyzes the iodination of tyrosine residues in thyroglobulin?
A) 5′-deiodinase
B) Tyrosine hydroxylase
C) Thyroid peroxidase
D) Phenylethanolamine-N-methyltransferase
Answer: C) Thyroid peroxidase

10. Thyroid hormones are stored in the gland as:
A) Free T3 and T4
B) Iodinated thyroglobulin in the colloid
C) Monoiodotyrosine (MIT)
D) Diiodotyrosine (DIT)
Answer: B) Iodinated thyroglobulin in the colloid

11. Which ion is essential for thyroid hormone synthesis?
A) Calcium
B) Magnesium
C) Iodine
D) Fluorine
Answer: C) Iodine

12. The sodium-iodide symporter is located on which surface of the thyroid follicular cell?
A) Basolateral membrane
B) Apical membrane
C) Lateral membrane
D) None of the above
Answer: A) Basolateral membrane

13. Which of the following inhibits thyroid peroxidase activity?
A) Iodine deficiency
B) Propylthiouracil
C) Thyroxine
D) TSH
Answer: B) Propylthiouracil

14. Which enzyme converts T4 to T3 in peripheral tissues?
A) Thyroid peroxidase
B) Deiodinase type III
C) Deiodinase type I
D) Deiodinase type II
Answer: C) Deiodinase type I

15. Which of the following increases basal metabolic rate most strongly?
A) Cortisol
B) Growth hormone
C) Thyroxine
D) Aldosterone
Answer: C) Thyroxine

16. Which of the following is not a direct action of thyroid hormones?
A) Increased oxygen consumption
B) Decreased heart rate
C) Increased protein synthesis
D) Increased glucose absorption
Answer: B) Decreased heart rate

17. Which of the following thyroid hormones is more potent?
A) T3
B) T4
C) Reverse T3
D) Thyroglobulin
Answer: A) T3

18. In hyperthyroidism, which of the following ECG findings is most typical?
A) Bradycardia
B) Sinus tachycardia
C) First-degree block
D) ST depression
Answer: B) Sinus tachycardia

19. Which autoantibody is pathognomonic for Graves’ disease?
A) Anti-TPO
B) Anti-thyroglobulin
C) TSH receptor–stimulating antibody
D) Anti-microsomal antibody
Answer: C) TSH receptor–stimulating antibody

20. In hypothyroidism, which lipid abnormality is common?
A) Low LDL
B) Low total cholesterol
C) High LDL cholesterol
D) Low triglycerides
Answer: C) High LDL cholesterol

21. Which of the following is seen in cretinism?
A) Exophthalmos
B) Mental retardation
C) Goiter with hypermetabolism
D) Tachycardia
Answer: B) Mental retardation

22. Myxedema is characterized by:
A) Hypoglycemia
B) Accumulation of mucopolysaccharides in interstitial tissues
C) Increased metabolic rate
D) Hypernatremia
Answer: B) Accumulation of mucopolysaccharides in interstitial tissues

23. Thyroid storm is most commonly precipitated by:
A) Hypoglycemia
B) Surgery or infection in hyperthyroid patients
C) Low iodine intake
D) Radioiodine therapy
Answer: B) Surgery or infection in hyperthyroid patients

24. The thyroid gland receives sympathetic fibers from:
A) Superior, middle, and inferior cervical ganglia
B) Celiac plexus
C) Vagus nerve
D) Hypoglossal nerve
Answer: A) Superior, middle, and inferior cervical ganglia

25. Blood supply to the thyroid gland is mainly through:
A) Lingual and facial arteries
B) Superior and inferior thyroid arteries
C) Internal carotid artery
D) Occipital artery
Answer: B) Superior and inferior thyroid arteries

26. Which structure forms the initial outpouching that gives rise to the thyroid diverticulum?
A) Lateral lingual swellings
B) Foramen cecum
C) Epiglottic tubercle
D) Thyrohyoid membrane
Answer: B) Foramen cecum

27. The thyroglossal duct normally obliterates by which embryonic week?
A) 4th week
B) 10th week
C) 20th week
D) Birth
Answer: B) 10th week

28. Which cell type lines the thyroid follicle and is responsible for thyroid hormone synthesis?
A) Parafollicular (C) cells
B) Endothelial cells
C) Follicular epithelial cells (thyrocytes)
D) Macrophages
Answer: C) Follicular epithelial cells (thyrocytes)

29. On histology, colloid appears as:
A) Basophilic granular cytoplasm
B) Amorphous eosinophilic material within follicles
C) Clear cells arranged in sheets
D) Spindle cell stroma
Answer: B) Amorphous eosinophilic material within follicles

30. Which arterial variation supplies the thyroid in about 3–10% of individuals and may arise from the aortic arch or brachiocephalic trunk?
A) Superior thyroid artery
B) Inferior thyroid artery
C) Thyroidea ima artery
D) Ascending pharyngeal artery
Answer: C) Thyroidea ima artery

31. Which vein forms the anterior venous drainage from the thyroid isthmus to the external jugular vein?
A) Superior thyroid vein
B) Middle thyroid vein
C) Anterior jugular vein
D) Internal jugular vein
Answer: C) Anterior jugular vein

32. The most important surgical landmark to identify the recurrent laryngeal nerve in thyroid surgery is:
A) Superior thyroid artery crossing point
B) Thyrohyoid membrane
C) Ligament of Berry (thyroid–tracheal ligament)
D) Cricothyroid muscle
Answer: C) Ligament of Berry (thyroid–tracheal ligament)

33. Which muscle overlies the thyroid gland anteriorly and must be divided or retracted during thyroidectomy?
A) Sternocleidomastoid
B) Sternohyoid and sternothyroid (infrahyoid) muscles
C) Omohyoid only
D) Platysma only
Answer: B) Sternohyoid and sternothyroid (infrahyoid) muscles

34. A thyroglossal cyst commonly presents as a midline neck swelling that moves with swallowing and tongue protrusion because it is attached to:
A) Hyoid bone only
B) Foramen cecum via thyroglossal tract
C) Cricothyroid membrane
D) Sternum
Answer: B) Foramen cecum via thyroglossal tract

35. Which of the following is TRUE regarding parafollicular C cells?
A) Derived from endodermal floor of pharynx
B) Secrete thyroid hormones T3 and T4
C) Derived from neural crest via ultimobranchial body and secrete calcitonin
D) Occupy the colloid lumen
Answer: C) Derived from neural crest via ultimobranchial body and secrete calcitonin

36. Which inhibitor of thyroid hormone synthesis acts primarily by inhibiting thyroid peroxidase and also blocks peripheral conversion of T4 to T3?
A) Methimazole
B) Propylthiouracil (PTU)
C) Levothyroxine
D) Potassium iodide
Answer: B) Propylthiouracil (PTU)

37. Which drug, given in high doses, acutely reduces thyroid hormone release by inhibiting proteolysis of thyroglobulin and hormone release?
A) Methimazole
B) Potassium iodide (Lugol’s iodine)
C) Levothyroxine
D) Lithium
Answer: B) Potassium iodide (Lugol’s iodine)

38. Radioactive iodine uptake (RAIU) test is most useful for distinguishing:
A) Thyroiditis from hypothyroidism
B) Graves’ disease (high uptake) from subacute thyroiditis (low uptake)
C) Papillary carcinoma from follicular carcinoma
D) Ectopic thyroid tissue from normal thyroid
Answer: B) Graves’ disease (high uptake) from subacute thyroiditis (low uptake)

39. Which autoantibodies are commonly found in Hashimoto thyroiditis?
A) TSH receptor–stimulating antibodies only
B) Anti-dsDNA antibodies
C) Anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin antibodies
D) Anti-insulin antibodies
Answer: C) Anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin antibodies

40. Which thyroid cancer is most strongly associated with previous childhood radiation exposure?
A) Medullary carcinoma
B) Follicular carcinoma
C) Papillary carcinoma
D) Anaplastic carcinoma
Answer: C) Papillary carcinoma

41. Which histologic feature is characteristic of papillary thyroid carcinoma?
A) Nuclear pleomorphism with keratin pearls
B) Follicular architecture with capsular invasion only
C) Orphan Annie eye nuclei and psammoma bodies
D) Spindle cells with storiform pattern
Answer: C) Orphan Annie eye nuclei and psammoma bodies

42. Which thyroid carcinoma arises from parafollicular C cells and produces calcitonin?
A) Papillary carcinoma
B) Follicular carcinoma
C) Medullary carcinoma
D) Anaplastic carcinoma
Answer: C) Medullary carcinoma

43. A solitary thyroid nodule with fine-needle aspiration showing Hurthle cells (oncocytic cells) most suggests:
A) Papillary carcinoma
B) Follicular/Hürthle cell neoplasm — requires surgical excision to assess capsular/vascular invasion
C) Thyroid lymphoma
D) Graves’ disease
Answer: B) Follicular/Hürthle cell neoplasm — requires surgical excision to assess capsular/vascular invasion

44. Which of the following tumors is least likely to take up radioactive iodine?
A) Papillary carcinoma
B) Follicular carcinoma
C) Medullary carcinoma
D) Follicular adenoma
Answer: C) Medullary carcinoma

45. Which laboratory pattern is typical for primary hypothyroidism?
A) Low TSH, high T4
B) High TSH, low free T4
C) Low TSH, low T4
D) High TSH, high T4
Answer: B) High TSH, low free T4

46. In secondary (central) hypothyroidism due to pituitary failure, expected findings are:
A) Elevated TSH and low T4
B) Low or inappropriately normal TSH with low T4
C) High TSH and high T4
D) Low TSH and high T4
Answer: B) Low or inappropriately normal TSH with low T4

47. Which deiodinase predominately mediates local intracellular T3 generation in the brain and pituitary?
A) Deiodinase type I (D1)
B) Deiodinase type II (D2)
C) Deiodinase type III (D3)
D) Monoamine oxidase
Answer: B) Deiodinase type II (D2)

48. Reverse T3 (rT3) is produced by:
A) Iodination of thyroglobulin in the follicle
B) Peripheral deiodination of T4 (inner-ring deiodination)
C) Secretion by parafollicular cells
D) Oxidation of T3 in the liver
Answer: B) Peripheral deiodination of T4 (inner-ring deiodination)

49. Which of the following is a tumor marker used in monitoring differentiated thyroid carcinoma after thyroidectomy?
A) Calcitonin
B) Serum thyroglobulin
C) PSA
D) Alpha-fetoprotein
Answer: B) Serum thyroglobulin

50. A patient with Graves’ ophthalmopathy has proptosis due to:
A) Increased intraocular pressure only
B) Autoimmune-mediated infiltration and inflammation of orbital fibroblasts leading to glycosaminoglycan deposition and extraocular muscle enlargement
C) Pituitary adenoma
D) Direct tumor invasion from thyroid
Answer: B) Autoimmune-mediated infiltration and inflammation of orbital fibroblasts leading to glycosaminoglycan deposition and extraocular muscle enlargement

51. Which clinical sign is most specific for thyrotoxicosis?
A) Weight gain
B) Dry coarse skin
C) Warm moist skin with heat intolerance and hyperreflexia
D) Cold intolerance
Answer: C) Warm moist skin with heat intolerance and hyperreflexia

52. Which of the following is the commonest cause of hypothyroidism worldwide?
A) Surgical removal of thyroid
B) Iodine deficiency
C) Autoimmune (Hashimoto) in iodine-sufficient areas; iodine deficiency worldwide historically
D) Radiation therapy
Answer: B) Iodine deficiency

53. Which physical sign suggests chronic hypothyroidism rather than acute?
A) Hyperreflexia
B) Non-pitting myxedema and coarse hair
C) Exophthalmos
D) Warm moist skin
Answer: B) Non-pitting myxedema and coarse hair

54. Which is the most sensitive test for detecting subclinical hypothyroidism?
A) Serum T3 level
B) Serum T4 level
C) Serum TSH level
D) Thyroid ultrasound
Answer: C) Serum TSH level

55. Which cells are responsible for the reabsorption of iodinated thyroglobulin from the colloid during hormone release?
A) Parafollicular C cells
B) Endothelial cells
C) Follicular epithelial cells via endocytosis
D) Lymphocytes
Answer: C) Follicular epithelial cells via endocytosis

56. Which surgical complication causes hoarseness due to unilateral vocal cord paralysis?
A) Injury to external branch of superior laryngeal nerve
B) Injury to hypoglossal nerve
C) Injury to recurrent laryngeal nerve
D) Transection of middle thyroid vein
Answer: C) Injury to recurrent laryngeal nerve

57. Which nerve supplies the cricothyroid muscle and is at risk when ligating the superior thyroid artery?
A) Recurrent laryngeal nerve
B) Superior laryngeal internal branch
C) Vagus nerve
D) External branch of superior laryngeal nerve (branch of superior laryngeal from vagus)
Answer: D) External branch of superior laryngeal nerve (branch of superior laryngeal from vagus)

58. In subacute (de Quervain) thyroiditis, the typical clinical course includes:
A) Painless thyroid enlargement with hypothyroidism only
B) Painful tender thyroid with transient thyrotoxicosis followed by hypothyroid phase
C) Chronic progressive hyperthyroidism
D) Isolated calcitonin elevation
Answer: B) Painful tender thyroid with transient thyrotoxicosis followed by hypothyroid phase

59. Which anti-thyroid medication is preferred during the first trimester of pregnancy?
A) Methimazole (MMI)
B) Propylthiouracil (PTU)
C) Radioactive iodine
D) Levothyroxine
Answer: B) Propylthiouracil (PTU)

60. Which histological feature is most characteristic of Hashimoto thyroiditis?
A) Sheets of metastatic cells
B) Follicular cells with orphan Annie nuclei
C) Lymphoid aggregates with germinal centers and Hurthle cell change
D) Spindle cell bundles with osteoid formation
Answer: C) Lymphoid aggregates with germinal centers and Hurthle cell change

61. Which of the following best describes follicular thyroid carcinoma spread?
A) Lymphatic spread to cervical nodes predominantly
B) Hematogenous spread to bone and lung due to capsular/vascular invasion
C) Direct perineural invasion only
D) No metastatic potential
Answer: B) Hematogenous spread to bone and lung due to capsular/vascular invasion

62. Which imaging modality is best for evaluating a cold thyroid nodule identified on radionuclide scan?
A) Chest X-ray
B) Ultrasound of the neck with Doppler
C) MRI brain
D) Colonoscopy
Answer: B) Ultrasound of the neck with Doppler

63. Anaplastic thyroid carcinoma typically presents in:
A) Young adults with slow growth
B) Elderly patients with rapidly enlarging neck mass and local invasion
C) Children after iodine exposure
D) Patients with Hashimoto only and excellent prognosis
Answer: B) Elderly patients with rapidly enlarging neck mass and local invasion

64. Which test is most useful to diagnose central (pituitary) hyperthyroidism due to TSH-secreting pituitary adenoma?
A) High TSH and low T4
B) Inappropriately normal or high TSH with elevated free T4 and pituitary MRI
C) Positive anti-TPO antibodies
D) Low free T4 with high TSH only
Answer: B) Inappropriately normal or high TSH with elevated free T4 and pituitary MRI

65. Which factor stimulates thyroid hormone synthesis by increasing TSH secretion?
A) High plasma iodide
B) Low circulating T4/T3 (negative feedback) and TRH stimulation from hypothalamus
C) Excess cortisol
D) High somatostatin levels
Answer: B) Low circulating T4/T3 (negative feedback) and TRH stimulation from hypothalamus

66. Which statement regarding neonatal hypothyroidism screening is correct?
A) Screening is unnecessary as signs are obvious at birth
B) Newborn screening using TSH (or T4) allows early detection to prevent neurodevelopmental delay
C) Radioiodine uptake is the screening test of choice
D) Only symptomatic infants are tested
Answer: B) Newborn screening using TSH (or T4) allows early detection to prevent neurodevelopmental delay

67. Which biochemical abnormality is typical in non-thyroidal illness syndrome (“euthyroid sick”)?
A) Elevated TSH with high T4
B) Low T3, normal or low T4, and normal TSH
C) High T3 and high T4 with low TSH
D) Isolated elevated TSH only
Answer: B) Low T3, normal or low T4, and normal TSH

68. Thyroid hormone increases basal metabolic rate primarily by:
A) Decreasing mitochondrial number
B) Upregulating Na⁺/K⁺-ATPase and mitochondrial oxidative enzymes
C) Inhibiting uncoupling proteins
D) Reducing oxygen consumption
Answer: B) Upregulating Na⁺/K⁺-ATPase and mitochondrial oxidative enzymes

69. Which of the following is a manifestation of neonatal thyrotoxicosis due to maternal Graves’ disease?
A) Hypotonia only
B) Tachycardia, irritability, low birth weight, and possible heart failure
C) Macroglossia only
D) Cretinism features appear immediately
Answer: B) Tachycardia, irritability, low birth weight, and possible heart failure

70. Which condition is associated with Riedel thyroiditis?
A) Viral infection only
B) Extensive fibrosis of thyroid extending to local structures; may be part of IgG4-related systemic disease
C) Isolated medullary carcinoma
D) High radioactive iodine uptake
Answer: B) Extensive fibrosis of thyroid extending to local structures; may be part of IgG4-related systemic disease

71. Which molecular marker is commonly used to confirm medullary thyroid carcinoma?
A) Thyroglobulin immunostain
B) TTF-1 positivity only
C) Calcitonin and CEA elevation; RET proto-oncogene mutation in familial cases
D) Elevated TSH receptor antibodies
Answer: C) Calcitonin and CEA elevation; RET proto-oncogene mutation in familial cases

72. Which genetic mutation is classically associated with familial medullary thyroid carcinoma and MEN2 syndromes?
A) BRAF V600E mutation
B) RAS mutation only
C) RET proto-oncogene mutation
D) p53 mutation only
Answer: C) RET proto-oncogene mutation

73. Which of the following is most likely to cause a transient increase in serum thyroglobulin?
A) Radioiodine ablation alone
B) Surgical manipulation of thyroid tissue or fine-needle aspiration
C) Levothyroxine replacement
D) Methimazole therapy
Answer: B) Surgical manipulation of thyroid tissue or fine-needle aspiration

74. Which feature distinguishes follicular adenoma from follicular carcinoma on histopathology?
A) Nuclear grooves and psammoma bodies
B) Presence of capsular and/or vascular invasion in carcinoma
C) Lymphoid infiltrates with germinal centers
D) Sheets of C cells secreting calcitonin
Answer: B) Presence of capsular and/or vascular invasion in carcinoma

75. Which physiological effect does thyroid hormone have on the cardiovascular system?
A) Decreases cardiac output
B) Reduces myocardial contractility
C) Increases heart rate, contractility, and cardiac output
D) Causes systemic vasoconstriction only
Answer: C) Increases heart rate, contractility, and cardiac output

76. A “cold nodule” on thyroid scan indicates:
A) Increased uptake and high function
B) Decreased or absent uptake — may represent malignancy or non-functioning tissue
C) Normal thyroid tissue
D) Graves’ disease activity
Answer: B) Decreased or absent uptake — may represent malignancy or non-functioning tissue

77. Which laboratory finding is characteristic of subclinical hyperthyroidism?
A) High TSH and high T4
B) Low (suppressed) TSH with normal T4 and T3
C) Elevated anti-TPO antibodies only
D) Low T3 with high TSH
Answer: B) Low (suppressed) TSH with normal T4 and T3

78. Which growth factor is implicated in thyroid follicular cell proliferation in goiter formation?
A) EGF only
B) Insulin only
C) TSH via its trophic action on follicular cells
D) Calcitonin only
Answer: C) TSH via its trophic action on follicular cells

79. Which histologic subtype of papillary thyroid carcinoma is associated with a worse prognosis and tall cell morphology?
A) Follicular variant only
B) Tall cell variant of papillary carcinoma
C) Medullary variant
D) Papillary microcarcinoma only
Answer: B) Tall cell variant of papillary carcinoma

80. Which condition can cause transient suppression of TSH due to excess exogenous thyroid hormone intake?
A) Iodine deficiency
B) Primary hypothyroidism
C) Factitious thyrotoxicosis from excessive levothyroxine ingestion
D) Hashimoto thyroiditis only
Answer: C) Factitious thyrotoxicosis from excessive levothyroxine ingestion

81. Which test helps to detect metastatic differentiated thyroid carcinoma after total thyroidectomy and radioiodine ablation?
A) Serum TSH only
B) Diagnostic whole-body radioiodine scan and stimulated serum thyroglobulin
C) Serum calcitonin only
D) Chest X-ray only
Answer: B) Diagnostic whole-body radioiodine scan and stimulated serum thyroglobulin

82. Which of the following is the best long-term management for toxic multinodular goiter in an elderly patient unfit for surgery?
A) Immediate surgery only
B) Methimazole for life only
C) Radioactive iodine therapy (131-I)
D) High-dose iodine infusion repeatedly
Answer: C) Radioactive iodine therapy (131-I)

83. Which physiological change occurs in pregnancy affecting thyroid function tests?
A) Decreased total T4 due to hemodilution
B) Increased total T4/T3 due to increased thyroxine-binding globulin (TBG) — free T4 often normal
C) Elevated TSH due to placental TRH only
D) Absence of detectable hCG effect on thyroid
Answer: B) Increased total T4/T3 due to increased thyroxine-binding globulin (TBG) — free T4 often normal

84. Which lab marker is most useful for monitoring response to therapy in medullary thyroid carcinoma?
A) Serum thyroglobulin only
B) Serum calcitonin and CEA levels
C) TSH receptor antibody
D) T3/T4 ratio
Answer: B) Serum calcitonin and CEA levels

85. Which of the following is TRUE about papillary thyroid microcarcinoma (≤1 cm)?
A) Always requires total thyroidectomy
B) Often has excellent prognosis; may be observed or treated depending on risk factors
C) Commonly metastasizes hematogenously
D) Typically non-radioiodine avid
Answer: B) Often has excellent prognosis; may be observed or treated depending on risk factors

86. Which physiologic stimulus increases expression of NIS (sodium-iodide symporter) in thyroid follicular cells?
A) Excess dietary iodine
B) Thyroid-stimulating hormone (TSH)
C) Cortisol
D) Calcitonin
Answer: B) Thyroid-stimulating hormone (TSH)

87. Which of the following is a WHO-recommended public health measure to prevent endemic goiter?
A) Universal vaccination against influenza
B) Universal salt iodization
C) Routine radioactive iodine distribution
D) High-dose selenium supplementation for all
Answer: B) Universal salt iodization

88. Which histologic finding indicates chronic autoimmune destruction in the thyroid?
A) Sheets of anaplastic cells
B) Lymphoid infiltration with germinal centers and Hurthle cell metaplasia
C) Pure colloid-filled large follicles only
D) Large multinucleated giant cells exclusively
Answer: B) Lymphoid infiltration with germinal centers and Hurthle cell metaplasia

89. Which pituitary hormone directly stimulates thyroid hormone synthesis?
A) ACTH
B) GH
C) TSH (thyrotropin)
D) Prolactin
Answer: C) TSH (thyrotropin)

90. During thyroid hormone synthesis, thyroglobulin is iodinated at tyrosyl residues to form MIT and DIT in which location?
A) Cytosol of parafollicular cells
B) Colloid of thyroid follicle lumen (apical surface mediated)
C) Endoplasmic reticulum of hepatocytes
D) Mitochondria of follicular cells
Answer: B) Colloid of thyroid follicle lumen (apical surface mediated)

91. Which is an indication for total thyroidectomy in differentiated thyroid cancer?
A) Microcarcinoma <5 mm only
B) Tumor >4 cm, bilateral disease, extrathyroidal extension, or distant metastases
C) Solitary benign adenoma only
D) Hyperthyroidism without nodules
Answer: B) Tumor >4 cm, bilateral disease, extrathyroidal extension, or distant metastases

92. Which of the following causes a decreased peripheral conversion of T4 to T3?
A) Hyperthyroidism only
B) Amiodarone, glucocorticoids, severe non-thyroidal illness
C) Excess selenium supplementation
D) High TSH state
Answer: B) Amiodarone, glucocorticoids, severe non-thyroidal illness

93. Which physical exam finding is typical of toxic multinodular goiter compared to Graves’ disease?
A) Diffuse bruit and exophthalmos only
B) Nodular irregular thyroid with less prominent ophthalmopathy
C) Pretibial myxedema exclusively
D) High anti-TSH receptor antibodies always present
Answer: B) Nodular irregular thyroid with less prominent ophthalmopathy

94. Which of the following patterns is most suggestive of subclinical hypothyroidism requiring monitoring?
A) Normal TSH and low T4
B) Low TSH and high T4
C) Mildly elevated TSH with normal free T4
D) High T4 with low T3 only
Answer: C) Mildly elevated TSH with normal free T4

95. Which immune-mediated phenomenon in Graves’ disease leads to diffuse thyroid enlargement?
A) Deposition of immune complexes only
B) Direct viral infection of thyroid
C) TSH receptor–stimulating immunoglobulins causing follicular hyperplasia and hypertrophy
D) Parafollicular cell hyperplasia only
Answer: C) TSH receptor–stimulating immunoglobulins causing follicular hyperplasia and hypertrophy

96. Which of the following is TRUE regarding use of recombinant TSH (rhTSH) in thyroid carcinoma follow-up?
A) rhTSH is used to suppress TSH only
B) rhTSH is used to stimulate thyroglobulin production and radioiodine uptake without thyroid hormone withdrawal
C) rhTSH cures metastatic disease by itself
D) rhTSH is equivalent to radioactive iodine therapy
Answer: B) rhTSH is used to stimulate thyroglobulin production and radioiodine uptake without thyroid hormone withdrawal

97. Which of the following laboratory features is typical in primary hyperthyroidism?
A) Elevated TSH, low T4
B) Suppressed TSH with elevated free T4 and T3
C) Low TSH with low T4 only
D) Normal TSH with low T3 only
Answer: B) Suppressed TSH with elevated free T4 and T3

98. Which of the following presents as a rapidly enlarging thyroid mass in an elderly patient and is almost always unresectable with poor prognosis?
A) Papillary carcinoma
B) Follicular adenoma
C) Anaplastic (undifferentiated) thyroid carcinoma
D) Medullary carcinoma with excellent prognosis
Answer: C) Anaplastic (undifferentiated) thyroid carcinoma

99. Which pathology is most associated with painless (silent) thyroiditis and postpartum thyroiditis?
A) Bacterial infection only
B) Subacute lymphocytic (painless) thyroiditis — transient thyrotoxicosis followed by hypothyroid phase
C) Riedel thyroiditis only
D) Papillary carcinoma only
Answer: B) Subacute lymphocytic (painless) thyroiditis — transient thyrotoxicosis followed by hypothyroid phase

100. Which clinical feature distinguishes primary hyperparathyroidism from thyroid disease (important differential in neck surgery)?
A) Hoarseness and dysphagia only
B) Hypercalcemia with kidney stones, bone pain — biochemical rather than thyroid hormone changes
C) Heat intolerance and weight loss only
D) Exophthalmos and pretibial myxedema
Answer: B) Hypercalcemia with kidney stones, bone pain — biochemical rather than thyroid hormone changes