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S2 - Mini #4 > Thyroid Histology: Biochemistry & Physiology > Flashcards

Thyroid Histology: Biochemistry & Physiology Flashcards

1
Q

In the hypothalamo-pituitary-thyroid axis, what form of feedback is physiological?

A. Positive feedback by TSH on the hypothalamus

B. Positive feedback by T3 and T4 on the pituitary

C. Positive feedback by T3 and T4 on the hypothalamus and pituitary

D. Negative feedback by TSH on the hypothalamus

E. Negative feedback by T3 and T4 on the pituitary

F. Negative feedback by T3 and T4 on the hypothalamus and pituitary

A

F

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2
Q

Which of the following hormones are produced by the thyroid gland? (choose all that apply)

A. Thyrotropin

B. Tri-iodothyronine

C. Thyroxine

D. Calcitriol

E. Calcitonin

A

B, C, and E

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3
Q

Which of the following choices correctly depicts the blood supply to the thyroid gland?

A. 1

B. 2

C. 3

D. 4

A

C.

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4
Q

When stimulated, what is the histological structure of the thyroid follicle?

A. Simple cuboidal epithelium surrounding a single follicular lumen

B. Stratified cuboidal epithelium surrounding a single follicular lumen

C. Stratified cuboidal epithelium surrounding multiple lumina

D. Simple columnar epithelium surrounding a single follicular lumen

E. Stratified columnar epithelium surrounding a single follicular lumen F. Stratified columnar epithelium surrounding multiple lumina

A

D. Simple columnar epithelium surrounding a single follicular lumen

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5
Q

In a thyroid follicle, what is the purpose of the follicular lumen?

A. Store iodide ions for use in thyroid hormone synthesis

B. Store thyroglobulin for use in thyroid hormone synthesis

C. Store calcitonin for use in parathyroid hormone synthesis

D. Store free thyroid hormone molecules in solution for thyroid hormone secretion

E. Store sodium and chloride ions for use in body water balance

A

B. Store thyroglobulin for use in thyroid hormone synthesis

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6
Q

In the figure below, identify the apical membrane.

A

A

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7
Q

In the figure below, identify A, B, C, and D.

A

A: Colloid.

B: Follicular cell.

C: Capillary.

D: Parafollicular (C) cells

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8
Q

Under normal circumstances, which of the following molecules has the most biological activity at its target tissues?

No, I won’t ask structures on the exam, but still, can you tell them apart?

A

C

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9
Q

In a person consuming a normal diet containing iodine, approximately what percent of this person’s iodine is stored within the thyroid gland?

A. less than 10

B. 25

C. 33

D. 50

E. 67

F. 75

G. greater than 90

A

E. 67

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10
Q

In the synthesis of thyroid hormone, in what state and through what cellular mechanism does iodine from the plasma enter the follicular cell?

A. It enters as iodide, through facilitated diffusion via a sodium symporter

B. It enters as iodide, through facilitated diffusion via a uniport

C. It enters as iodide, through primary active transport

D. It enters as iodine, through endocytosis of iodine-containing proteins

E. It enters as iodine, through facilitated diffusion via a sodium symporter

F. It enters as iodine, through facilitated diffusion via a uniport

G. It enters as iodine, through primary active transport

H. It enters as iodine, through endocytosis of iodine-containing proteins

A

A. It enters as iodide, through facilitated diffusion via a sodium symporter

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11
Q

In the synthesis of thyroid hormone, in what state and through what cellular mechanism does iodine from the follicular cell exit into the follicular lumen?

A. It exits as iodide, through facilitated diffusion via a sodium symporter

B. It exits as iodide, through facilitated diffusion via a uniport

C. It exits as iodide, through primary active transport

D. It exits as iodine, through exocytosis of iodine-containing proteins

E. It exits as iodine, through facilitated diffusion via a sodium symporter

F. It exits as iodine, through facilitated diffusion via a uniport

G. It exits as iodine, through primary active transport

H. It exits as iodine, through exocytosis of iodine-containing proteins

A

B. It exits as iodide, through facilitated diffusion via a uniport

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12
Q

In the synthesis of thyroid hormone, in what compartment does the actual production step of T3 and T4 synthesis take place?

A. Within the endoplasmic reticulum of the follicular cell
B. Within the vesicle being moved to the follicular membrane
C. In the lumen of the thyroid follicle
D. Within the lumen of the secondary lysosome of the follicular cell
E. In the plasma following secretion of precursor molecules from the follicular cell

A

C. In the lumen of the thyroid follicle

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13
Q

In the secretion of thyroid hormone, in what state and through what cellular mechanism does iodine from the colloid enter the follicular cell?

A. It enters as iodide, through facilitated diffusion via a sodium symporter

B. It enters as iodide, through facilitated diffusion via a uniport

C. It enters as iodide, through primary active transport

D. It enters as iodine, through endocytosis of iodine-containing proteins

E. It enters as iodine, through facilitated diffusion via a sodium symporter

F. It enters as iodine, through facilitated diffusion via a uniport

G. It enters as iodine, through primary active transport

H. It enters as iodine, through endocytosis of iodine-containing proteins

A

H. It enters as iodine, through endocytosis of iodine-containing proteins

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14
Q

On a quantitative basis, how is most secreted thyroid hormone transported in the plasma?

A. As thyroxine, freely dissolved in the plasma

B. As thyroxine, bound to albumin

C. As thyroxine, bound to transthyretin

D. As thyroxine, bound to thyroid binding globulin

E. As triiodothyronine, freely dissolved in the plasma

F. As triiodothyronine, bound to albumin

G. As triiodothyronine, bound to transthyretin

H. As triiodothyronine, bound to thyroid binding globulin

A

D. As thyroxine, bound to thyroid binding globulin

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15
Q

Through what mechanism does thyroid hormone alter the activity of its target cells?

A. Conversion of T4 into T3 in the cytoplasm, then T3 binding to a nuclear receptor, then stimulation of transcription

B. Conversion of T3 into T4 in the cytoplasm, then T4 binding to a nuclear receptor, then stimulation of transcription

C. Conversion of T4 into T3 in the cytoplasm, then T3 binding to a cytoplasmic receptor, then stimulation of transcription

D. Conversion of T3 into T4 in the cytoplasm, then T4 binding to a cytoplasmic receptor, then stimulation of transcription

A

A. Conversion of T4 into T3 in the cytoplasm, then T3 binding to a nuclear receptor, then stimulation of transcription

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16
Q

Through what physiological mechanism does leptin modulate secretion of thyroid hormone?

A. It has a direct effect on thyroid follicular cells, increasing hormone secretion

B. It has a direct effect on arcuate and paraventricular neurons, increasing TRH secretion

C. It has a direct effect on pituitary thyrotrophs, increasing TSH secretion

D. It has a direct effect on thyroid follicular cells, decreasing hormone secretion

E. It has a direct effect on arcuate and paraventricular neurons, decreasing TRH secretion

F. It has a direct effect on pituitary thyrotrophs, decreasing TSH secretion

A

B. It has a direct effect on arcuate and paraventricular neurons, increasing TRH secretion

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17
Q

What is the primary function of thyroid hormone?

A. It increases cardiac output

B. It increases food intake

C. It increases metabolic rate

D. It increases sweating

E. It increases growth and maturation.

A

C and E

18
Q

Which of the following result in the adaptive response of reduced T3 formation?

A. Fasting for a prolonged period

B. Exposure to cold environment

C. Exposure to human chorionic gonadotropin in early pregnancy

D. Becoming critically ill

A

A and D

19
Q

Thyroid hormone has many permissive actions. In cardiac muscle, which hormone or neurotransmitters’ effects on cardiac function is most significantly increased because of proteins whose production was the result of thyroid hormone action?

A. Acetylcholine

B. Epinephrine

C. Norepinephrine

D. Atrial natriuretic peptide

E. Insulin

A

B

(and to a lesser extent C)

20
Q

Which of the following effects of thyroid hormone increase heat production in the body?

A. Increased uncoupling protein-1 (UCP1) in brown adipose tissue

B. Increased bile acid synthesis

C. Increased differentiation of chondrocytes

D. Increased osteoblast activity in bone

E. Increased sodium-potassium pumps

A

A and E

21
Q

Which of the following effects of thyroid hormone are not directly related to metabolism?

A. Increased production of sex-hormone-binding-globulin

B. Increased mitochondrial biogenesis

C. Increased futile cycling in carbohydrate and fat metabolism

D. Increased free fatty acids in the plasma

E. Increased absorption of dietary glucose

A

A. Increased production of sex-hormone-binding-globulin

22
Q

Which of the following are effects of thyroid hormone in white adipose tissue?

A. Increase in triglyceride synthesis

B. Incorporation of triglycerides from plasma

C. Decrease in number of lipases

D. Stimulation of adipose cell differentiation

E. Stimulation of thermogenesis

A

D. Stimulation of adipose cell differentiation

23
Q

Which of the following are effects of thyroid hormone?

A. Increased cardiac output

B. Increased plasma triglycerides

C. Increased brain maturation

D. Increased fertility in adults of reproductive age

E. Increased peripheral vascular resistance

A

A, C, and D

24
Q

Which of the following disorders would be least likely to produce any symptoms in affected patients?

A. Deficiency of TBG in plasma

B. Deficiency in ability to produce TSH

C. Deficiency in ability to produce thyroxine

D. Overproduction of TSH

E. Overproduction of thyroxine

A

A. Deficiency of TBG in plasma

25
Q

Which of the following conditions are the most likely causes of thyrotoxicosis, a condition characterized by heat intolerance?

A. Primary hypothyroidism

B. Primary hyperthyroidism

C. Secondary hypothyroidism

D. Secondary hyperthyroidism

E. Iatrogenic hypothyroidism

F. Iatrogenic hyperthyroidism

A

B and D

(slight chance of F)

26
Q

A 26-year-old patient presents with chief complaint of feeling tired. She reveals that over the past year she has gained 30 pounds without trying. She says she cannot abide being in a cold environment, including in this office. Vital signs include a body temperature of 35.9 degrees C and a calculated BMI of 33.0 kg/m2. Physical exam reveals an enlarged area in the anterior portion of her neck which when palpated does not seem to contain nodules. A sample of her blood is sent to the laboratory. What are the most likely findings in this patient?

A. TSH is high, thyroxine is low, TBG is normal

B. TSH is high, thyroxine is low, TBG is low

C. TSH is high, thyroxine is high, TBG is normal

D. TSH is low, thyroxine is low, TBG is normal

E. TSH is low, thyroxine is low, TBG is low

F. TSH is low, thyroxine is high, TBG is normal

A

A. TSH is high, thyroxine is low, TBG is normal

Diffuse goiter: Hypertrophy and/or hyperplasia, usually caused by overstimulation through the TSH system.

versus Multinodular goiter: Multiple nodules and cysts present: multifocal hyperplastic condition of unknown origin; common in females, favored by iodine deficiency

27
Q

In the patient above, if her problem turns out to be a medullary carcinoma, what hormones would most likely be elevated in her plasma?

A. thyroxine

B. triiodothyronine

C. thyrotropin

D. calcitonin

E. calcitriol

A

C and D

28
Q

What is the most common cause of hyperthyroidism?

A. TSH-secreting pituitary adenoma

B. Follicular adenoma

C. Follicular carcinoma

D. Graves disease

E. Autoimmune thyroiditis

A

D. Graves Disease

29
Q

What form of thyroid dysfunction is characteristic of Hashimoto disease?

A. Primary hyperthyroidism

B. Primary hypothyroidism

C. Secondary hyperthyroidism

D. Secondary hypothyroidism

A

B. Primary hypothyroidism

30
Q

In the western diet, most salt sold in stores is supplemented with iodine. What condition or conditions is this supplementation intended to prevent?

A. Cretinism

B. Primary hypothyroidism

C. Secondary hypothyroidism

D. Graves disease

E. Hashimoto disease

F. Thyrotoxicosis

A

A and B

31
Q

Laboratory Tests: Total T3 and T4 & when it’s not useful

A

For hypothyroidism and hyperthyroidism, but uninformative when TBG level is abnormal.

32
Q

Laboratory Tests: Free T3

A

for assessment of hypothyroidism or hyperthyroidism.

33
Q

Laboratory Tests: TSH

A

to distinguish between primary and secondary forms of hypo- and hyperthyroidism. Abnormal TSH with normal free T3 is “subclinical” hypothyroidism or hyperthyroidism.

34
Q

Laboratory Tests: Calcitonin

A

screening test for medullary carcinoma

35
Q

Graves Disease

A

This is the most common cause of hyperthyroidism.

Autoimmune: stimulatory IgG antibody to TSH receptor

Colloid depletion and papillary proliferation of follicular epithelium

36
Q

Autoimmune Thyroiditis (Hashimoto disease)

A

Most common form of hypothyroidism (Initially transient hypo- or hyperthyroidism, eventually lasting hypothyroidism).

Antibodies to thyroperoxidase, thyroglobulin and/or TSH receptor

Treated with levothyroxine (Rx for all hypothyroidism)

37
Q

Deficiency of TBG

A

X-linked

T3 and T4 are 20% - 30% of normal

No signs of hypo- or hyperthyroidism

Thyroid status is normal because the pituitary gland senses the free (unbound) hormone, and regulates it into the normal range.

38
Q

Thyroid Disorders: Hypothyroidism

A

Underproduction of thyroid hormone

Primary: Failure of the thyroid gland, TSH high
Secondary: Failure of the pituitary gland, TSH low

39
Q

Thyroid Disorders: Hyperthyroidism

A

Overproduction of thyroid hormone

40
Q

Thyroid Disorders: Thyrotoxicosis

A

Thyroid hormone excess of any cause (hyperthyroidism or iatrogenic)

S2 - Mini #4 (18 decks)

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