Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

2023 Systems Phys > Endocrine - Thyroid Physiology > Flashcards

Endocrine - Thyroid Physiology Flashcards

1
Q

What are the classic hormone groups?

A

Amine hormones (Tyrosine derivatives)
Steroids
Peptides
Proteins

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

Do thyroid hormones behave like amine hormones?

Do thyroid hormones have rapid enzymatic synthesis?

A

No

Thyroid hormones are slow

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

Do thyroid hormones behave like amine hormones?

Are thyroid hormones stored in secretory granules?

A

No

Thyroid hormones are stored outside the cell that synthesized it

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

Do thyroid hormones behave like amine hormones?

Are thyroid hormones water soluble?

A

No

Iodides present prevent water solubility

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

Do thyroid hormones behave like amine hormones?

Do thyroid hormones have a long or short half-life?

A

Long

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

Do thyroid hormones behave like amine hormones?

Do thyroid hormones have a membrane receptor?

A

No

Thyroid Hormones hve intracellular receptors

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

Where are Thyroid hormones made?

A

In thyroid follicular cells

Sphereical epithelial cells

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

Define:

Colloid

What is it?

A

Stored thyroid hormones in the center of follicular cells

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

What are the three major steps of thyroid hormone synthesis?

A
  1. uptake and concentration of iodide (I-) in the gland
  2. Oxidation and incorporation of I- in tyrosine’s phenol ring
  3. Coupling of two iodinated tyrosines to form T4 or T3
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Thyroglobulin is secreted and iodinated by…

A

Thyroid epithelial cells

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

What is the effect of low iodine in the body?

A

Decreases the rate of thyroid synthesis

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

What is the effect of high levels of iodine on the body?

A

Suppresses thyroid synthesis

Wolff-Chaikoff effect

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

What is the purpose of storing iodine in the body?

A

It protects the body from iodinen deficiency for an extended period of time

Stored I= within the gland is 100x greater than daily need (80 ug)

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

TH synthesis: Step 1

How is I- transported into the thyroid gland?

A

vs its electrochemical gradient by a 2Na+-I- symporter in the basement membrane of thyroid epithelial cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

TH synthesis: Step 1

____ block active transport of I-

A

ClO4-
SCN-

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

TH Synthesis: Step 2

Thyroglobulin

Define

A

Scaffold to make Thyroid Hormone

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

TH Synthesis: Step 2

Tyrosine Iodination

A

I- is oxidized and incorporated into tyrosine both by the enzyme thyroid peroxidase (TPO)

Oxidize I-l Iodinize Tyrosine

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

TH Synthesis: Step 2

The residues of thyroglobulin form…

A

MIT or DIT

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

TH Synthesis: Step 3

2 DIT molecules couple to form…

A

T4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

TH Synthesis: Step 3

1 MIT and 1 DIT couple to form…

A

T3

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

What is the ratio of T4 to T3 synthesized by the thyroid gland?

A

10-20 T4 : 1 T3

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

How is thyroid hormone secreted?

A

Thyroglobulin enter thyroid follicular cell via endocytosis
Lysosomal proteases hydrolyze the thyroglobulin
T4 and T3 are released
MITs and DITs aew deiondinated and I- recycles

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

_ is the active form of Thyroid Hormone

A

T3

4X more potent than T4

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

____% of thyroid hormone secreted is T4

A

90%

T4 is a prohormone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
____% of thyroid hormone secreted is T3
9%
26
____% of thyroid hormone secreted is rT3
1%
27
What happens to T4?
Peripheral conversion of T4 to T3 through the action of specific deiondinases
28
_ thyroid hormone increases with cold temperature?
T3
29
_ thyroid hormone increases during starvation
rT3
30
What is the purpose of rT3?
To eat up energy to prevent T3 use
31
5'MD is highly active and converts T4 into...
T3
32
5MD is highly active and converts T4 into...
rT3
33
What occurs when there is a decrease in T4 to T3 conversion?
Fasting Malnutrition Physicalo Trauma Drugs Systemic Illness Old Age
34
If starving and cold, which factor wins out?
Make more T3
35
How do T3 and T4 circulate the blood?
70% bound to thyroxine-binding globulin (TBG) bindingh protein 29.5% bound to prealbumin and albumin Low levels of free hormone
36
What is the purpose of T4 and T3 as free hormones?
Binding proteins create a reservoir of hormone protects from acute changes in thyroid gland function
37
If free T4 decreases suddenly... | What happens to bound T4?
The constant release and rebinding to binding proteins can replace lost free T4
38
What if the liver makes more binding protein? | This can happen during pregnancy
Alterations in RBG do not disturb biolgical function (if thyroid gland is normal)
39
What determined hyper/hypo thyroidism?
The concentration of free hormone
40
What is a major stimulator of thyroid hormone stimulation?
Thyroid - Stimulating Hormone (TSH) | TSH is under negative feedback control
41
What is the function of TSH?
Stimulates almost every step in the pathway of TH synthesis Stimulates growth (goiter) and vascularity (Bruit) of thyroid gland
42
Feedback control of Thyroid Hormone is sensitive. | Explain
Changes in thyroidh ormone levels of only 10-30% are eno9ugh to change TSH in the opposite direction
43
What is the relationship between T3 and TSH?
↑T3 ↓TSH
44
What characteristic of T4 gives it a half life of 6 days?
T4 has a higher affinity for TBG
45
Why is T3 the biologically active hormone?
T3 has a higher affinity for thyroid receptor
46
When treating hypothyroidism, why do we give synthetic T4 (Levothyroxine) instead of synthetic T3 (Liothyronine)?
**Levoythroxine** - mimics true physiology, low cost, lacks allergens, easy lab measurements, long half-life (↑ compliance), more stable **Liothyronine** - shorter half life (multiple doses/day), expensive, harder to monitor, higher activity (dangerous)
47
What is the function of T3?
Brain maturation Bone growth β - adrenergic effects BMR increases | 4 B's
48
Actions of Thyroid Hormones | Pathway
T4 → 5'-iodinase →T3 →T3 binds nuclear receptor → DNA transcription → mRNA translation → synthesis of new proteins → 4B'a functions
49
T3's function in bone growth:
Growth formation Bone maturation T3 stimulates secretion of GH and remodeling of mineralized bone ## Footnote TH accelerates shedding of skin and hair
50
T3's function in BMR:
↑Na-K ATPase ↑O2 Consumption ↑Heat production ↑# and size of mitochondria | Regulates BMR
51
T3's function in metabolism:
↑Glucose absorption ↑Glycogenolysis ↑Gluconeogenosis ↑Lipolysis ↑Protein synthesis and degredation
52
T3's function in cardiovascular:
↑CO | ↑HR, SV, contractility, SBP, ↓DBP, vasodilation, ↓ SVR
53
# Define Synpathomimetic | What is it? What does it do?
Many actions of high thyroid hormone levels resemble ↑ed SNS activity reinforces CV resoponses to Epi and NE Permissive effect for Epi and NE on lipolysis, glyconeolysis, and GNEO
54
Symptoms of Hyperthryoidism:
Nervousness Insomnia Anxiety Restlessness Sweating Heat intolerance Tremor Weight Loss Palpitations Tachycardia
55
T3's effect in CNS development:
T3 receptor is expressed in the brain throughout fetal life Activity of 5' deiodinase is augmented Degredation of T3 is diminished
56
TH enhances a variety of neurally controlled functions:
↑speed and amplitude of reflexes, wakefulness, alertness, responsiveness to various stimuli, awareness of hunger, memory and learning capacity Normal emotional tone
57
What happens to a fetus if a. mother has hypothyroidism and T3 is defificent in utero?
Impaired growth of the cerebal and cerebellar cortex Imparied proliferation of axons and branching dendrites Impaired myelinization Irreversible brain damage if not treated immediately after birth Biochemically: ↓RNA and protein content, protein synthesis, enzymes for DNA synthesis, NT receptors, NT synthesis
58
Symptoms of Congenital Hypothyroidism:
Short stature Malformed legs Dull expression Intellectual disabilities delayed puberty muscle weakness
59
# Define Hypothyroidism
A deficiency of thyroid hormones | Under active thyroid
60
Symptoms of Hypothyroidism
Fatigue, lethargy Weight Gain Cold intolerance (↓BMR) Muscle aches, stiffness Somnolence (drowsiness) Thinning hair Dry Skin Prolonged reflex times Depression Mental Slowness Constipation Amenorrhea (heavy/irregular periods) Puffy face (myxedema) Goiter ## Footnote Water retention
61
Primary causes of hypothyroidism
Thyroid failure Iodine insufficiency ↓T4&T3 ↑TSH Hashimoto's Thyroiditis | Autoimmune, thyroid antibodies damage thyroid ## Footnote Feedback works
62
Secondary Causes of Hypothyroidism
Pituitary or hypothalamic failure ↓T4 &T3 ↓TSH Feedback wont work | No goiter, not a problem with thyroid
63
# Define: Hyperthyroidism
Excess thyroid hormones
64
Symptoms of Hyperthyroidism:
Heat intolerant (↑ BMR) Weight loss Palpitations Nervousness, anxiety, irritability Tremor Moist, warm skin ↑defecation frequency Goiter Bruit over thyroid Pretibial myxedema (Grave's Disease) Fatigure Exopthalamos, lid retraction Forward siaplacement of eyeballs
65
Primary causes of Hyperthyroidism
Graves Disease ↑T4 and T3 ↓TSH Thyroid Stimulating Immunoglobulins (TSI) Hypersecreting thyroid tumor (Toxic adenoma)
66
# Define Graves Disease
Autoimmune disease in which antibodies target thyroid receptor activating thyroid hormone synthesis | Stimulate gland, Goiter
67
Secondary Causes of Hyperthyroidism
Excess TSH or TRH Feedback isnt working ↑T4&T3 ↑TSH
68
What happens if you have low TSH and T3/T4?
Tropic Hormone Deficiency Secondary Hypothyroidism
69
What happens if you have High TSH and Low T3/T4?
Primary failure of target endocrine organ Primary Hypothyroidism
70
What happens if you have High TSH and High T3/T4?
Seecondary hyperthyroidism Autonomous secretion of tropic hormone TSH-secreting tumor | No feedback
71
What happens if you have Low TSH and High T3/T4?
Primary Hyperthyroidism Autonomous secretion of target endocrine organ | Graves Disease; goiter

2023 Systems Phys (41 decks)

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