7.3 Flashcards

1
Q

What are the 2 thyroid hormones?

A
T3= Triiodothyronine
T4= Thyroxine
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2
Q

What is NIS

A

Na/I cotransporter

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3
Q

What can compete the I- on the NIS?

A

Thyocyanate (SCN-)

Pertechnate (TcO4-)

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4
Q

How does Iodine pumped ot to the colloid?

A

Pendrin- Cl/I antiporter

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5
Q

What oxidize I- to I2?

A
Thyroid Peroxidase (TOP)
With the help of DUOX2
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6
Q

How does T3,T4 circulate in the blood?

A

80% bound to TBG
15% bound to Transthyretin
5% bound to Albumin

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7
Q

How much of T3, T4 is free?

A
  1. 5% of T3 is free

0. 02% of T4 is free

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8
Q

What happens to thyroid hormones in hepatic failure?

A

TBG levels drop -> increase in free thyroid hormones -> negative feedback -> less thyroid hormones are produced

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9
Q

When can an increase in TBG happen?

A

Pregnancy

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10
Q

What happens to T4when its absorbed by a tissue?

A

5’ Iodinase converts T3 to T4

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11
Q

When do 5’ Iodinase being inhibited?

A

During starvation in skeletal muscle to allow lower metabolic rate

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12
Q

What can decrease 5’ Iodinase activity?

A
Starvation
Pregnancy
Stress
Hepatic failure
Renal failure
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13
Q

What can increase 5’ Iodinase activity?

A

Obesity

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14
Q

Types of 5’ Iodinase

A

Type 1: T4->T3 in kidney, liver, skeletal muscle
Type 2: T4->T3 in CNS, Pituitary
Type 3: T4->rT3 Inactivation

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15
Q

What happens after the conversion of T4 to T3 inside the target cell?

A

T3 binds thyroid receptor on the nuclear membrane -> get inside nucleus and find Thyroid Responsive Element on DNA with RXE

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16
Q

(Thyroid Hormones Effects)

Effects on Basal Metabolic rate?

A

Increase O2 consumption (except brain, gonads, spleen)

This will increase body heat

17
Q

(Thyroid Hormones Effects)

Metabolism?

A
Increase glucose absorption
Gluconeogenesis
Glycogenolysis
Protein synthesis
Protein degradation 

General catabolic effect

18
Q

(Thyroid Hormones Effects)

Cardiovascular?

A

Increase CO
Increase SV, HR
All by induce B1 adrenergic R in the heart (will increase sympathetic activity)

19
Q

(Thyroid Hormones Effects)

Respiratory?

A

Rate and minute volume increases

Erythropoietin stimulated -> RBC synthesis increases

20
Q

(Thyroid Hormones Effects)

Growth?

A

Thyroid hormones work with GH and Somatomedins to promote general growth

21
Q

(Thyroid Hormones Effects)

CNS?

A

Myelination - childhood
Synapses formation - childhood
Cell migration - childhood

22
Q

(Thyroid Hormones Effects)

Autonomic NS?

A

Induce expression of a and B adrenergic R

23
Q

Structure of TSH

A

a subunit is non specific

B subunit is specific to TSH

24
Q

How does TSH stimulate T3/T4 production?

A
  1. Increase NIS (I uptake, Iodination, TG endocytosis)
  2. mRNA synthesis for TPO, DUOX2, NIS
  3. Increase cell number and size (Goiterrr)
25
What will stimulate the Hypothalamus to secrete TRH
Increased food intake | Decreased temparture
26
What are the causes for Hypothyroidism?
Iodine deficiency Genetic issues Inflammation
27
Symptoms in infants of Hypothyroidism?
Cretinism (mental retardation, dwarfism, big tongue)
28
Symptoms in adults of Hypothyroidism?
1. Myxoedema- proteoglycans and glycoproteins are high in CT (usually TH breaks them) 2. Hoarse voice 3. Dry skin 4. Weight gain 5. Sensitive to cold 6. Slow speech 7. Depression
29
What are the causes for Hyperthyroidism?
Increased TSH | TSH like antibodies (Graves disease)
30
Symptoms of Hyperthyroidism?
1. Increased BMR 2. Muscle weakness 3. Anxiety