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24 A&P II > Lecture 6: Thyroid (Exam I) > Flashcards

Lecture 6: Thyroid (Exam I) Flashcards

1
Q

Where does thyroid hormone secretion start?
What is released?

A
  • Hypothalamus
  • The hypothalamus releases TRH (thyrotropin-releasing hormone).
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2
Q

What can trigger the hypothalamus to secrete TRH?

A
  • ↑ stress
  • ↓ temp
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3
Q

Describe the circulatory path from hypothalamus to thyroid (include pertinent released hormones).

A

Hypothalamus - TRH → portal system → anterior pituitary - TSH → general circulation → thyroid.

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4
Q

What occurs whenever TSH reaches the thyroid?

A

T₃ and T₄ production is stimulated.

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5
Q

What two things are necessary for thyroid hormone and precursor production?

A
  • Iodine
  • Tyrosine
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6
Q

What is the result of a single iodine molecule combined with a tyrosine base?

A
  • Monoiodotyrosine (T₁)
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7
Q

What is the result of two iodine molecules combined with a tyrosine base?

A
  • Di-iodotyrosine (T₂)
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8
Q

How is T₃ created? What is its proper name?

A
  • Triiodothyronine (T₁ + T₂ = T₃)
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9
Q

How is T₄ created? What is its proper name?

A
  • Thyroxine (T₂ + T₂ = T₄)
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10
Q

What structural difference separates a molecule with a -tyrosine suffix vs a -thyronine suffix?

A
  • One benzene ring = -tyrosine
  • Two benzene rings = -thyronine
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11
Q

What hormones are secreted from the adenohypophysis?

A
  • TSH (thyroid-stimulating hormone)
  • GH (growth hormone)
  • LH (luteinizing hormone)
  • FSH (follicle-stimulating hormone)
  • Prolactin
  • Corticotropin
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12
Q

What organ does FSH interact with?

A
  • Ovaries
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13
Q

What organ does LH interact with?

A
  • Ovaries
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14
Q

What organ does prolactin interact with?

A
  • Mammary glands
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15
Q

What is the pathway for Corticotropin causing increased serum insulin levels?

A

Adenohypophysis - corticotropin → Adrenal cortex - ACH → increased glucose → pancreas increases insulin release.

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16
Q

Which thyroid hormone is more active intracellulary?

A

T₃

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17
Q

What percentage of T₃ vs T₄ is delivered to the tissue?

A
  • T₃ = 7% of hormone delivered.
  • T₄ = 93% of hormone delivered.
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18
Q

How do thyroid hormones affect mitochondria?

A
  • T₃-T₄ increase the size and number of mitochondria.
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19
Q

How do thyroid hormones affect the Na⁺K⁺ATPase pump?

A
  • ↑Thyroid hormones cause ↑ ICF Na⁺ = increased Na⁺K⁺ATPase activity.
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20
Q

Do thyroid hormone increase gluconeogenesis or glycolysis?

A
  • Trick question. Thyroid hormones increase both gluconeogenesis and glycolysis.
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21
Q

_________ will convert T₄ to T₃ for intracellular use.

A
  • Iodinase
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22
Q

How do thyroid hormones get into cells?
What happens when they are in the cell?

A
  • Lipid diffusion
  • Gene transcription causing upregulating of essentially all cellular activity.
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23
Q

What innervates the voicebox?
What are these branches of?
Why are they named the way they are?

A
  • Right & Left Recurrent Pharyngeal Nerves
  • Branches of the vagus nerve
  • “Recurrent” due to looping characterstic. The right loops under the subclavian artery and the left loops under the aortic arch.
24
Q

Where would an emergent cricothyrotomy be performed? Describe its location.

A
  • A. Ligament immediately inferior to the thyroid cartilage.
25
Q

What considerations should be given to the thyroid when performing an emergency airway?

A
  • The thyroid might be in the way and is highly vascularized with arteries.
26
Q

What is an increase in thyroid size called? What can occur from this?

A
  • Goiter
  • Increased pressure on the voicebox = hoarseness. Possible compression of tracheal rings in worst case scenarios.
27
Q

What is the main source of dietary iodine intake?
How much iodine is needed per year?

A
  • Iodized salt
  • 50mg of Iodine needed per year. No single dose, need a steady consumption.
28
Q

What is the rate-limiting step for thyroid precursor formation?

A
  • H₂O₂ (Peroxidase)
    I₂ → H₂O₂ → I + tyrosine = precursors.
29
Q

What type of molecule are T₃ and T₄ ?
Why is this pertinent?

A
  • Steroids
  • Need transport proteins for circulatory movement and lipid solubility makes membrane diffusion easy.
30
Q

What transport proteins carry thyroid hormones?
(list in order of importance)

A
  1. TRG (Thyroxine-binding globulin)
  2. Thyroxine-binding pre-albumin
  3. Albumin
31
Q

Where are thyroid transport proteins created?
Why is this clinically relevant?

A
  • Thyroid transport proteins are made in the liver and are subject to deficiencies from various liver pathologies (ex. cirrhosis)
32
Q

Describe the process for thyroid hormone creation inside the thyroid itself as well as secretion.

A
  • Thyroglobulin combines iodine + tyrosine to produce 60-70 T₃ & T₄ per thyroglobulin.
  • Thyroglobulin is dissolved to secrete hormones.
33
Q

When does T₄ effect peak when injected intravenously? Why?

A
  • Lag time of ~ 10 days due to gene transcription MOA of T₃ & T₄
34
Q

What two causes of hyperthyroidism were discussed in lecture?

A
  • Primary Tumor
  • Autoimmune (Graves disease)
35
Q

What is the pathology of Graves disease?

A
  • TSH receptors are stimulated via auto-antibodies thus eventually increasing T₃ and T₄.
36
Q

What are the four generalized treatment options for hyperthyroidism?

A
  1. Surgery
  2. Radioactive Iodine
  3. Drugs
  4. Iodine Overdosing
37
Q

What are the possible consequences of surgery for hyperthyroidism?

A
  • Possible loss of ability to speak
  • Possible bleeding
38
Q

Why is radioactive iodine a good option for hyperthyroidism treatment?

A
  • Selectively shrinks thyroid gland with no other tissues uptaking iodine.
39
Q

What drugs are used to treat hyperthyroidism?
What should be known the MOA of each?
What is the general drawback of both?

A
  1. Thiocyanate - competitor for Iodine transporter
  2. Propothiouracil - Inhibits peroxidase

Both take 60 - 90 days to work.

40
Q

What drugs are used to treat hyperthyroidism?
What should be known about the MOA of each?
What is the general drawback of both?

A
  1. Thiocyanate - competitor for Iodine transporter
  2. Propothiouracil - Inhibits peroxidase

Both take 60 - 90 days to work.

41
Q

How would Iodine overdosing actually treat hyperthyroidism?

A
  • Overwhelms Iodine oxidizing process (thus inhibiting formation of MIT, DIT, T₃, & T₄)
42
Q

What what drug has a large amount of Iodine in it? How much?
Does this drug cause hypothyroidism or hyperthyroidism?

A
  • Amiodarone (35% Iodine by mass)
  • Both ↓THY & ↑THY are possible from excess Iodine.
43
Q

What are four possible causes of hypothyroidism?

A
  1. Iodine deficiency
  2. Autoimmune disease (Hashimoto’s)
  3. Genetic mutations
  4. Idiopathic (5% of population)
44
Q

What is Hashimoto’s disease?
What is the treatment?

A
  • Autoimmune disease where antibodies attack thyroid tissue.
  • Steroids & plasmapheresis
45
Q

What is the clinical significance of hypothyroidism?

A

↓ NMJ excitability

  • ↓ awareness
  • longer wake times
  • susceptibility to NMBs
46
Q

What is the consequence of hypothyroidism for younger patients?
What is the treatment?

A
  • Cretinism (stunted growth)
  • Levothyroxine (difficult to dose & adhere to).
47
Q

What are the general cardiac responses to increased thyroid hormone?

A
  • ↑ HR
  • ↑ SV
  • No change in MAP
  • ↑ PP
  • ↓ cholesterol
  • ↓ triglycerides
48
Q

Why is there an increased pulse pressure when the body is exposed to increased thyroid hormones?

A
  • ↑sBP & ↓dBP
  • Occurs from peripheral vasodilation so nutrients can flow in and byproducts can flow out.
49
Q

Why is cholesterol decreased in hyperthyroidism?

A
  • Cholesterol gets used for energy and has increased GI excretion as well.
50
Q

What are the general neuromuscular effects of hyperthyroidism?

A
  • ↑ awareness & harder to put to sleep
  • ↑ NMJ excitability = tremor
51
Q

What symptoms would you expect to see from thyroid storm?
What does acute care involve?

A
  • ↑HR, ↑Temp, ↑RR, etc.
  • Supportive care (ex. cooling)
52
Q

What disorder might be expected from these lab values:
- ↓ TSH
- ↓ TRH
- ↑ T₄

A
  • Primary T₄ secreting tumor
53
Q

What disorder might be expected from these lab values:
- ↑ TSH
- ↓ TRH
- ↑ T₄

A
  • Primary TSH secreting tumor
54
Q

What disorder might be expected from these lab values:
- ↓ TSH
- ↑ T₃
- ↑ T₄

A
  • Grave’s Disease

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55
Q

What disorder might be expected from these lab values:
- ↓ T₄
- ↑ TRH
- ↑ TSH

A
  • Iodine deficiency

24 A&P II (24 decks)

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