Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Block 3; Week 6 Michelle > Thyroid O'Driscoll > Flashcards

Thyroid O'Driscoll Flashcards

1
Q

How much does the thyroid gland?

A

15-20 grams

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where is the thyroid gland located?

A

below the larynx

anterior to the trachea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe the cellular composition of the thyroid gland.

A 
follicular cells
endothelial cells
parafollicular (C) cells
fibroblasts
lymphocytes
adipocytes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What happens in the follicular cells?

A

thyroid hormone synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the fcn of the endothelial cells of the thyroid gland?

A

they line the capillaries that provide blood to the follicles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the function of the parafollicular (C) cells?

A

production of calcitonin, important in calcium metabolism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe the morphology of the thyroid follicular cells.

A

they are closed off follicles
lined w/ cuboidal epithelial cells
filled w/ colloid: mainly composed of thyroglobulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What does the apical surface of the follicular/epithelial cells face? The basolateral side?

A

Apical: faces the lumen
Basolateral: faces the interstitium, the capillaries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the 2 main thyroid metabolic hormones?

A

T4 (thyroxine) & T3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What percentage of thyroid secretions are T4? What % are T3?

A

T4: 93% of secretions
T3: 7% of secretions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Which has a greater plasma conc’n: T3 or T4?

A

T4!!!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Which is more potent: T4 or T3?

A

T3!!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a second source of T3, aside from the thyroid gland?

A

Much of the T4 is converted into T3 once it reaches the tissues. This happens thru peripheral monodeiodination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the 5 factors involved in thyroid hormone synthesis?

A 
TSH
Thyroglobulin
Iodine
Membrane Transporters
Enzymes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the structure of thyroglobulin?

A

large glycoprotein w/ multiple tyrosine residues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Where is the thyroglobulin synthesized, secreted, & stored?

A

Synthesized: thyroid follicular cells
Secreted: thru apical membrane into follicular lumen
Stored: in the colloid, in the follicular lumen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the function of thyroglobulin?

A

it is a scaffold in the follicular lumen for thyroid hormone synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Why is iodine important in the diet? How much iodine do you need each week?

A

important for thyroid hormone synthesis
1mg required per week…we get enough in our table salt
**most preventable global cause of mental retardation
**in higher elevations, less iodine in the soil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the basic steps of thyroid hormone synthesis?

A
  1. Iodide Trapping
  2. Formation & Secretion of Thyroglobulin
  3. Iodide Oxidation & coupling of Iodide w/ thyroglobulin
  4. Endocytosis of Thryoglobulin & release of thyroid hormones
  5. Recycling Iodide
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is iodide trapping?

A

process of concentrating iodide in the cell

influenced by TSH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe in detail Stage 1 of thyroid hormone synthesis, the iodide trapping.

A

Iodide is in the capillaries by the follicles.
NIS: Sodium Iodide Symporters bring iodide into the follicle cell.
This movement is driven by the Na/K pump.
Iodide gets into the follicular lumen via pendrin (a chloride-iodide counter transporter)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

T/F The concentration of iodide in the follicular cells is much lower than in the blood.

A

False. It is 30X higher. Thus, when transporting iodide into the follicular cell, it is up a conc’n gradient.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What physical characteristic is important for the follicular cells to transport iodide?

A

their morphological polarization. Wider near the capillaries, room for transporters.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the second stage of thyroid hormone synthesis? How does this work?

A

thyroglobulin is formed & secreted.
it is formed in the ER & Golgi & secreted into the follicular colloid
each molecule of it has a ton of tyrosine AA
the thyroid hormones are made within the thyroglobulin molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What is stage 3 of thyroid hormone synthesis? How does it work?
the iodide is oxidized & coupled w/ thyroglobulin Details: *iodide gets into the lumen of the follicle & is oxidized by thyroperoxidase (TPO) *once the iodine is oxidized it can combine w/ tyrosine AA w/i the thyroglobulin molecule (called organification)
26
Tyrosine is first iodized to ____ & then to ____.
MIT & then to DIT
27
What is T4 composed of? What is T3 composed of?
T4: DIT + DIT T3: MIT + DIT
28
What is reverse T3?
An inactive form of T3 that can be formed.
29
What all does TPO or thyroperoxidase catalyze?
oxidation of iodide organification of iodine/iodination of tyrosines on the scaffold of thyroglobulin Synthesis of T3 & T4
30
What happens if someone doesn't have activity of TPO?
their thyroid hormone production rate falls to zero
31
Where is some thyroid hormone stored? How much is stored?
follicular colloid, a part of the thyroglobulin molecule **enough is stored here to supply the body with thyroid hormone for 2-3 months-->thus when you experience iodine deficiency you won't see the fall in levels for several months...
32
Where are the plasma proteins that bind thyroid hormones synthesized?
the liver
33
What percentage of T3 & T4 are bound to plasma proteins?
99%
34
What are the 3 types of binding proteins for T3 & T4? What % of T3/T4 bind to each?
TBG: Thyroxine-Binding Globulin (70%) Prealbumin (15%) Albumin (15%)
35
What is another name for pre albumin?
transthyretin
36
What percentage of T3 is found free? What % of T4?
Free T3: 0.3% | Free T4: 0.03%
37
What's the deal with plasma proteins? Do they get overwhelmed easily?
``` They don't get easily saturated. Implications: *they are unsaturated *They can store 3X their amount *sudden changes in hormone secretion don't effect free thyroid very much... ```
38
Describe how pregnancy can alter thyroid hormone levels.
``` Pregnancy High Estrogen Levels Binding Protein Synthesis increases New Equilibrium b/w free & bound hormone Increase in total thyroid hormone levels ```
39
Why do thyroid hormones have a large reserve? Why do they have a delayed clearance?
b/c they are bound to binding proteins (longer half-life)...stored in the blood & peripheral tissues
40
What is the half life of T3? T4?
T3: 1 day T4: 6 days
41
Why is the half life of T3 so much shorter than T4?
b/c the binding proteins have a higher affinity for T4.
42
How are thyroid hormones excreted?
conjugated to glucuronic acid & excreted in bile
43
Which has a greater biological activity? T3 or T4?
T3!!
44
What is the main source of T3 that is used by the body?
that that is converted from T4 in the peripheral tissues
45
What percentage of the thyroid hormone released from the gland is T3? T4?
93% T4 | 7% T3
46
What % of the T4 is deiodinated to form T3?
40%
47
Which deiodinases are responsible for turning T4 into rT3?
DI & DIII
48
Which deiodinases are responsible for turning rT3 into T2?
DI & DII
49
Which deiodinases are responsible for turning T4 into T3?
DI & DII
50
Which deiodinases are responsible for turning T3 into T2?
DI & DIII
51
Where is deiodinase type I most active?
liver kidney thyroid
52
Where is deiodinase Type II most active?
``` brain pituitary thyroid skeletal muscle cardiac muscle ```
53
Where is deiodinase Type III most active?
Brain Placenta Fetal Tissues
54
Does DI cut the outer or inner ring?
both!
55
Does DII cut the outer or inner ring?
outer ring only
56
Does DIII cut the outer or inner ring?
inner ring only
57
DI is a major source of what kind of T3?
T3 that is circulating
58
DII is a major source of what kind of T3?
T3 that is produced in tissues
59
What is the vibe of DIII? What does it protect?
It decreases T3 levels & protects the fetus & adult brain.
60
Which form of thyroid hormone has a shorter latent period: T3 or T4?
T3-->active faster, after only 6-12 hours
61
What happens after TSH binds to the TSH receptor on the thyroid gland?
G protein coupled receptor, an increase in cAMP. | Genomic & Non-genomic effects
62
What are the genomic effects of TSH on the thyroid gland?
Increased Gene Transcription | Increase in NIS, Thyroglobulin, TPO, NO synthase, Growth factors
63
What are the non-genomic effects of TSH on the thyroid gland?
An increase in cAMP increased proteolysis of thyroglobulin (means more T3 & T4 release) NIS activity increases (increased iodide trapping) Increase in tyrosine iodination (T3 & T4 synthesis)
64
What is the effect of TH on TSH or TRH (from the hypothalamus)?
It decreases them both. Negative feedback inhibition. It also decreases the TRH receptor on the anterior pituitary. this allows for a constant conc'n of free T3 & T4.
65
Thyroid Hormone Receptors (TRs) have higher affinity for T3 or T4? What types of receptors are these? What effect do they have?
Higher affinity for T3 This is found in peripheral tissues nuclear receptors-->change transcription Increase in growth, cardiac output & metabolism
66
Which TH effect is faster: genomic or non-genomic?
Non-genomic is faster.
67
Where are the main sites of the non-genomic response?
plasma membrane cytoplasm cell organelles-->mitochondria
68
What is the basic response to thyroid hormone?
Enhanced mobilization of carbs, fats, & proteins Increase in O2 consumption Increase in basal metabolic rate & heat production
69
What does thyroid hormone do to carbohydrate metabolism?
Increased uptake of glucose in the cells Enhanced gluconeogenesis Increased glucose absorption in the GI tract
70
What does thyroid hormone do to lipid metabolism?
Mobilizes fat stores Increases Plasma FFA conc'n Accelerates FA oxidation Increases LDL receptors on liver-->decreases plasma cholesterol
71
In a case of hypothyroidism: what would happen to plasma cholesterol?
It would increase plasma cholesterol.
72
What would thyroid hormone do to nitrogen metabolism?
Increased Protein Synthesis | An even greater increase of protein degradation
73
Why is it that an increase in thyroid hormone can cause a relative vitamin deficiency?
b/c with the increase in production of many enzymes-->need more vitamins
74
If a person had hyperthyroidism & weight gain-->why would that be?
b/c increased thyroid hormone causes increased metabolic rate & appetite. Sometimes the appetite predominates.
75
What is the effect of thyroid hormone on the skeletal system?
important for growth & bone maturation
76
What is the effect of thyroid hormone on the central nervous system?
essential for maturation of the CNS during the perinatal period cerebral & cerebellar growth myelination vascularization axonal & dendritic density cell migration & differentiation affected
77
What is the effect of thyroid hormone on the cardiovascular system?
Blood flow & cardiac output increases (vasodilation) Increase in heart rate Increase in heart strength b/c of increase in enzymatic activity Increase in systolic pressure Increase in pulse pressure
78
What would an intense, crazy increase in thyroid hormone do to heart strength?
It would decrease it b/c of long-term protein catabolism
79
What is the effect of T3 on cardiovascular hemodynamics?
``` T3 causes tissue thermogenesis Body needs to get rid of heat Decrease in systemic vascular resistance via NO production Diastolic BP lowers Decrease in afterload RAAS activated Increase in Preload Increase in Cardiac Output ```
80
What is the effect of thyroid hormone on respiration?
It increases the rate of metabolism & therefore O2 utilization... Activates mechanisms that increase resp rate & depth
81
What is the effect of thyroid hormone on GI?
It increases appetite & food intake. It increases secretions & motility Too much thyroid hormone: increased frequency of bowel movements Too little thyroid hormone: constipation
82
What is the effect of thyroid hormone on sleep?
exhausts muscles & CNS Too much thyroid hormone: always tired, but can't sleep Too little thyroid hormone: sleep 12-14 hrs/day
83
What does thyroid hormone do to muscle vigor?
a little increase in thyroid hormone: muscles react w/ vigor Too much thyroid hormone: weakness b/c of protein catabolism Too little thyroid hormone: sluggish muscles **fine muscle tremor: sign of hyperthyroidism
84
What does thyroid hormone do to the CNS?
increases excitatory effects Hyper: nervousness, psychoneurotic tendencies Hypo: lack of energy, dulled mental capacity
85
What does thyroid hormone do to the autonomic nervous system?
increases the effects of sympathetic stimulation
86
What does thyroid hormone do to pancreatic secretions?
More thyroid hormone more glucose metabolism more insulin secretion
87
What does thyroid hormone do to pituitary secretions?
More thyroid hormone Less TSH More GH
88
What are the main categories of primary hyperthyroidism?
Graves' Disease Hyperfunctioning Thyroid Nodules Therapy-Induced Hyperthyroidism (excess T3 & T4 substitution) Thyroiditis
89
What are the main categories of secondary hyperthyroidism?
TSH secreting pituitary adenomas
90
What are the symptoms of hyperthyroidism?
``` Highly Excitable Heat Intolerance Increased Sweating Weight Loss Increased frequency of bowel movements Muscle Weakness Nervousness Fatigue w/o sleep Hand tremor ```
91
What are the main categories of primary hypothyroidism?
``` Hashimoto's Disease Endemic Colloid Goiter (dietary iodine deficiency) Congenital Hypothyroidism (Cretenism) Defects of Hormone Synthesis Treatments for Hyperthyroidism Thyroid Surgery & Radiation Therapy ```
92
What are the main categories of secondary hypothyroidism?
Disorders of the anterior pituitary or hypothalamus
93
What are the symptoms of hypothyroidism?
``` Fatigue Muscular Sluggishness Low HR & CO Weight Gain Constipation Mental Sluggishness Myxedema Cold Intolerance Hoarseness Goiter Hypercholesterolemia ```
94
What type of a disease is Graves'?
diffuse toxic goiter | an autoimmune disease
95
What are some examples of hyper functioning thyroid nodules? What happens w/ these?
Examples: toxic adenoma, toxic multinodular goiter Causes hyper secretion of thyroid hormone Low TSH other part of thyroid (not toxic nodule) inhibited from excreting thyroid hormone.
96
What's the deal w/ thyroiditis causing primary hyperthyroidism?
this is inflammation of the thyroid gland | can cause excess thyroid hormone stored in the gland to leak out into the bloodstream
97
With TSH secreting pituitary adenomas...what disease do you have? What are the T4, T3 & TSH levels like?
This is secondary hyperthyroidism TSH high T4 & T3 high **b/c of the adenoma, can't stop producing TSH even tho there is negative feedback from thyroid hormones
98
If you have goiter, do you have hyper or hypothyroidism?
Could have either. Goiter is present in either.
99
In Grave's Disease...do you have hypo or hyperthyroidism? What is the mechanism? What are the levels of T3, T4, & TSH?
High T3 & T4 Low TSH (b/c of negative feedback Hyperthyroidism **antibodies called TSI: thyroid-stimulating immunoglobulins form & activate the TSH receptors on the thyroid gland.
100
What are 3 main symptoms of Grave's Disease?
Goiter (hypertrophy & hyperplasia of the thyroid gland) Pretibial Myxedema (deposition of CT-->cutaneous & dermal edema) Graves' opthalmopathy
101
What are the 2 forms of Graves' opthalmopathy?
``` Exophthalmos (protusion of the eyeballs) Thyroid Stare (eyes going in strange directions) ```
102
What causes exophthalmos?
the autoimmune rxn causes edema of the retro-orbital tissues & degeneration of the extra-ocular muscles
103
What is an example of something that causes secondary hypothyroidism? What does this do to TSH, T3, T4 levels?
Disorders of the anterior pituitary or hypothalamus-->this impairs TSH release T3, T4 & TSH will all be low
104
With Hashimoto's Disease...what are the TSH, T3, & T4 levels? What are some of the things that can cause this?
High TSH Low T3 & T4 **antibodies against thyroglobulin, thyroperoxidase, TSH receptor blockers **sometimes thyroiditis can deteriorate the thyroid tissue & lead to fibrosis--stops secretion of thyroid hormones
105
What can you see in a histo slide of thyroid gland that indicates Hashimoto's disease?
lymphocyte infiltration of the thyroid gland | a part of the cell-mediated immune response
106
What TSH, T3, & T4 levels are seen in endemic colloid goiter? Describe how iodine deficiency can cause this.
High TSH Low T3 & T4 Iodine deficiency: a bunch of thyroglobulin secreted into the colloid...goiter. No T3 & T4 produced, but bunches of TSH try to make it happen.
107
What are 4 things aside from dietary iodine deficiency that can cause endemic colloid goiter?
Deficiency of Iodide Trapping Mechanism Deficiency Peroxidase System Deficient coupling of iodinate tyrosines in thyroglobulin Deficiency of the deiodinase enzyme (no I recycling)
108
What is another name for cretinism? What are 2 things that can cause it?
congenital hypothyroidism | congenital lack of the thyroid gland & dietary iodine insufficiency
109
When do the symptoms of congenital hypothyroidism first appear? What are they?
a few weeks after birth b/c they were depending on mom's thyroid hormones sluggish movements retarded physical & mental development short, stocky appearance (b/c skeletal muscle is more retarded than soft tissue growth)
110
What is the treatment for Cretinism?
daily oral thyroxine & iodide replacement | need to begin soon after discovered before damage becomes permanent, critical time window.

Block 3; Week 6 Michelle (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions