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Thyroid Flashcards

1
Q

A complete lack of thyroid secretion results in what changes to basal metabolic rate?

A

Decreases by 40-50%

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2
Q

Extreme excesses of thyroid secretion can result in what changes to basal metabolic rate?

A

Increase by 60-100% above normal

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3
Q

Where is the thyroid located?

A

Butterfly shaped gland located immediately below the larynx, anterior and to each side of the trachea

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4
Q

T/F: The thyroid is one of the smallest glands?

A

False; one of the largest endocrine glands at 15-20 grams

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5
Q

What three hormones are produced by the thyroid?

A
  1. Thyroxine (T4)
  2. Triiodothronine (T3)
  3. Reverse T3 (rT3)
    (also calcitonin)
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6
Q

What type of cells is the thyroid made of?

A

Made of follicles of cuboidal epithelial cells surrounding a colloid matrix

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7
Q

Which two hormones are the most important thyroid hormones for metabolic control?

A

Thyroxine (T4) and thriidothyronine (T3).

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8
Q

T3 or T4: Which thyroid hormone makes up 93% of the hormones that the thyroid secretes?

A

T4

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9
Q

T3 or T4: Which is more potent?

A

T3 is four times more potent.

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10
Q

T3 or T4: Which one is cleared more rapidly?

A

T3

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11
Q

Which endocrine gland releases Thyrotropin Releasing Hormone (TRH)?

A

Hypothalamus

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12
Q

What action does Thyrotropin Releasing Hormone have on the anterior pituitary?

A

Releases Thyroid Stimulating Hormone (TSH).

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13
Q

What action does TSH have on the thyroid gland?

A

Releases T3 and T4

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14
Q

T/F: Most thyroid hormone is free in the body and not bound?

A

False; 99% is bound to either Thyroxine binding globulin (TBG) or albumin

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15
Q

What 4 things occur in the peripheral tissues once T4/T3 gets there?

A
  1. Convert all T4 to T3
  2. Increases gene synthesis
  3. Increases protein and enzyme production
  4. Increases the size and number of mitochondria
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16
Q

What are thyroid hormones’ effects on fat metabolism?

A
  1. Mobilizes lipids
  2. Decreases fat stores
  3. Decreases cholestrol
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17
Q

Why might a decrease in body weight not always be tied to increased thyroid hormone levels?

A

It also increases appetite

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18
Q

What are the 11 effects of thyroid hormones?

A
  1. Stimulation of carbohydrate metabolism
  2. Stimulation of fat metabolism
  3. Increased vitamin requirement
  4. Increased basal metabolic rate
  5. Decreased body weight
  6. CV effects
  7. CNS effects
  8. Muscular effects
  9. Sleep effects
  10. Endocrine effects
  11. Reproductive/sexual effects
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19
Q

What are some of the CV effects?

A
  1. Increased blood flow secondary to vasodilation
  2. Increased CO
  3. Increased HR and inotropy
  4. Increased SBP, decrease DBP, No change in MAP
  5. Increased respiration with more CO2 production
  6. Increased number and affinity of Beta-adrenergic receptors
  7. Decreased number of cardiac alpha-adrenergic receptors
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20
Q

What CNS changes occur with thyroid hormones?

A

Increased mentation, but also increased anxiety and neurosis

21
Q

What are some symptoms of hypothyroidism?

A
  1. Cold intolerance
  2. Depression
  3. Fatigue
  4. Joint pain
  5. Thin, brittle fingernails
  6. Weakness
  7. Weight gain
22
Q

Which type of hypothyroidism is associated with the pituitary gland not secreting TSH?

A

Secondary Hypothyroidism

23
Q

Which type of hypothyroidism is associated with the thyroid gland itself?

A

Primary Hypothyroidism

24
Q

What are the two most common reasons for primary hypothyroidism?

A
  1. Autoimmune Hashimoto’s Thyroiditis

2. Surgical removal of thyroid tissue

25
What are some other (less common) reasons for Primary Hypothyroidism?
1. Inadequate dietary iodine 2. Radiation exposure 3. Lithium
26
An issue with the hypothalamus would causes which type of hypothyroidism?
Tertiary Hypothyroidism
27
Low TSH is associated with what type of hypothyroidism?
Secondary because it is related to the pituitary gland
28
Low TRH is associated with what type of hypothyroidism?
Tertiary because it is related to the hypothalamus
29
Low T3/T4 and normal TSH is associated with what type of hypothyroidism?
Primary Hypothyroidism
30
What does hypothyroidism in infancy lead to?
Mental retardation and growth deficits (Cretinism)
31
What is the most severe form of hypothyroidism?
Myxedema coma
32
What are the s/s of myexdema coma?
1. Rare condition 2. Triggered by illness, infection, exposure to cold, medicines 3. Symptome= coma, hypoventilation, hypoglycemia, hypotension, hypothermia
33
What would a patients labs look like with primary hypothyroidism?
Low T3/T4 and high TSH
34
What is major component of why hypothyroidism lab testing is only 85-90% accurate?
Affected by Thyroxin Binding Globulin (if its bound, it can't be detected)
35
What are 5 anesthetic management tips for hypothyroidism?
1. Be aware of "crash on induction" risk 2. Ketamine for induction 3. Pancuronium or Rocuronium for vagolytic effects 4. VA not recommended d/t myocardium sensitive to depression 5. A-line with presence of cardiac failure
36
Definition of thyroiditis?
Inflammation of thyroid that causes release of excessive hormone, but not increased production
37
Definition of thyrotoxicosis?
An oversupply of thyroid hormones on peripheral tissues
38
What are some symptoms of hyperthyroidism?
``` Palpitations Nervousness Insomnia Hair loss Tachycardia Fatigue ```
39
What is the most common cause of hyperthyroidism?
Grave's Disease
40
What is Grave's disease?
Autoimmune disease that causes activation of TSH receptor by autoantibodies. Causes multinodular goiter. Hallmark sign exophthalmos
41
What are pharmacological tx for hyperthyroidism?
1. Antithyroids= Methimazole or propulthiouracil (PTU) 2. Propranolol 3. Radioactive iodine 4. eventually surgery
42
When does thyroid storm typically occur?
6-18 hours postop
43
What are causes of thyroid storm?
Surgery, infection, trauma, toxemia, DKA
44
What are the three major symptoms of thyroid storm?
1. Hyperthyroid 2. Hyperthermia 3. Hypovolemia
45
Tx for thyroid storm?
Labetolol/inderal, cortisol, tylenol, cooling blankets, fluids, and glucose
46
What are major anesthetic management tips for hyperthyroid?
1. Checking airway (goiters) 2. Tx of hemodynamic hyperdynamism 3. Administer anti-thyroid drugs 4. Tx volume depletion 5. Correct electrolyte abnormalities
47
Postoperative considerations following thyroidectomy?
1. RLN damage 2. SLN damage 3. Hematoma/bleeding 4. Hypocalcemia 5. Tracheomalacia
48
What would unilateral RLN damage cause? Bilateral?
Unilateral=hoarseness | Bilateral=Aphonia, stridor, aspiration
49
Why would hypocalcemia follow thyroidectomy?
d/t inadvertent removal of parathyroid glands

Endocrine (6 decks)

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