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[OS 202] C > [5] Thyroid > Flashcards

[5] Thyroid Flashcards

1
Q

Most important enzyme in the production of Thyroid Hormones

A

Thyroid Peroxidase

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2
Q

Usual Amount of Iodine in Diet

A

400ug

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3
Q

Daily Requirement of Iodine in Non-Pregnant and Pregnant Adults

A

Non: 150 mcg/d
Preg: 200mcg/d

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4
Q

Importance of Thyroid Hormone in Fetuses

A

Brain Development

Branching of Axons and Dendrites

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5
Q

How long can a normal human’s Iodine stores last?

A

2 months (7,500mg)

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6
Q

Where is Iodine usually trapped?

A

Lacrimal glands, salivary glands

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7
Q

How do you assess the thyroid?

A

Urine Iodine Levels

Thyroid Scan w/ Uptake

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8
Q

Is iodine uptake increased or decreased in patients with iodine deficiency?

A

Additional iodine uptake occurs in patients with abnormal iodine levels

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9
Q

Describe: Iodide Trap/NIS

A

2 Na per 1 I via secondary active transport

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10
Q

Effect of Increased TSH in NIS

A

Increased Expression

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11
Q

Prevalence of Endemic Goiters

A

10%

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12
Q

Cause: Goiters

A

Lack of Iodine causes the pituitary to increase secretion of TSH to trap more iodine causing enlargement of the thyroid

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13
Q

What helps Iodine exit the follicular lumen?

A

Pendrin

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14
Q

How does T3 or T4 enter the cell?

A

Through Megalin

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15
Q

Thyroglobulin Components

A

MIT 7
DIT 6
T4 2
T3 0.2

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16
Q

Production Values

A

T4: 90ug
T3: 35ug
rT3: 35ug (Reverse T3)

17
Q

Storage Values of Thyroid Hormones

A

90% T4
10% T3
1% rT3

18
Q

What Thyroid hormone is produced more in iodine deficient states?

A

T3, T4 is a stored inactive form

19
Q

Transport Molecules of Thyroid Hormones

A

Thyroid Binding Globulin: 70%
Transthyretin: 15%
Albumin: 15%

20
Q

Why is TBG important in Transport?

A
  • Enables lipid soluble hormone to traverse blood stream
  • Storage for considerable amount of hormone
  • Prevent loss of small hormone molecules into the urine, conserving Iodine
21
Q

Effect of Estrogen on TBG

A

Increase

22
Q

Effect of Hepatitis on TBG

A

Liver is the main producer of TBG, as a result of the hepatitis more of it would leak out and cause the increase in TBG

23
Q

In what situation would there be increased rT3 production?

A

High catabolic states such as in sepsis

24
Q

Location: Type 1 Deiodinase

A

Areas of high blood flow

Thyroid
Liver
Kidney
Skeletal Muscle

25
Q

Function: Type 1 Deiodinase

A

Most conversion from T4 to T3 to supply sufficient T3 elsewhere

26
Q

Location: Type 2 Deiodinase

A

Brain

Pituitary

27
Q

Function: Type 2 Deiodinase

A

Converts T4 to T3

High affinity so maintains high intracellular T3 concentrations

28
Q

Function: Type 3 Deiodinase

A

Converts T4 to rT3

High affinity

29
Q

Location: Type 3 Deiodinase

A

Brain
Skin
Placenta

30
Q

Location:

TR(B-1) Receptor
TR(A-1)
TR(B-2)

A

B-1: Brain
A-1: Cardiac, Skeletal
B-2: Pituitary

31
Q

How does Thyroid Hormone increases cardiac output?

A

Direct:
(+) Inotropic Effect
(+) Chronotropic Effect
Lowers SVR by dilating arterioles

Indirect:
(+) Heat Production
(-) PVR
(-) DBR

32
Q

Effect: TR(B-2) Receptor Mutation

A

Absent TSH suppression, resulting in hyperthyroidism

33
Q

Effect: TR(A-1) Receptor Mutation

A

Hypothyroidism, because even if the hormone is on the receptor the cascade will not work

34
Q

Pathway: Hypothalamo-Pituitary-Thyroid Axis

A

Hypothalamus -> TRH
Pituitary -> TSH
Thyroid -> T4 + T3 (Negative Feedback to both Hypothalamus and Pituitary)

35
Q

Describe: Regulation of Hormone Production by Leptin

A

Adipose tissue produces Leptin, a satiety signal

This would stimulate the PV nucleus to cause an increase in T4/T3 to increase metabolism to breakdown adipose

36
Q

Window of time to correct cretinism

A

2 weeks

[OS 202] C (6 decks)

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