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pharmacology > Thyroid and Antithyroid Agents > Flashcards

Thyroid and Antithyroid Agents Flashcards

1
Q

In which species is hypothyroidism most common?

A

Dog (and horse)

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2
Q

In which species is hyperthyroidism most common?

A

Cat

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3
Q

What is the most prevalent form of hypothyroidism?

A

Lymphocytic thyroiditis

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4
Q

What type of process is lymphocytic thyroiditis?

A

Autoimmune

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5
Q

What are the clinical signs associated with hypothyroidism?

A

Lethargy, weakness, coma, obesity, cold intolerance, skin lesions (myxedema), alopecia, infertility

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6
Q

What is the #2 underlying cause of demodicosis?

A

Hypothyroidism

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7
Q

What are the clinical signs associated with hyperthyroidism in a cat?

A

Weight loss, polyphagia, PU/PD, heat intolerance, tachycardia, tachypnea, hair loss, diarrhea, vomiting

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8
Q

1 MIT + 1 DIT = ?

A

T3

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9
Q

DIT + DIT = ?

A

T4

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10
Q

Where is thyroglobulin synthesized?

A

Follicular cells

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11
Q

In dogs, ____% of T4 and T3 are bound by plasma proteins.

A

99%

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12
Q

Plasma protein binding of T4 and T3 in the dog is greater than or less than that in the human?

A

Less than

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13
Q

What are the 3 plasma proteins that bind thyroid hormone?

A
  1. Thyroxin-binding globulin
  2. Transthyretin
  3. Albumin
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14
Q

In which species is thyroxin-binding globulin NOT found?

A

Cat

Rabbit

Rodent

Bird

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15
Q

Place the following in order of the most protein-bound T4 to the least: ruminants, horses, primates, dogs.

A

Primates > ruminants > horses > dogs

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16
Q

The more thyroid hormone bound to plasma protein, the longer its half life. What are the half lives of T4 and T3 in the dog?

A

T4 = 8 - 16 hours

T3 = 5 - 6 hours

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17
Q

What is the T4 dosage in a dog?

A

> 20 uL / kg / day

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18
Q

What is the T4 dosage in a human?

A

50 - 150 uL / day

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19
Q

How does estrogen affect TBG synthesis?

A

Increases TBG synthesis

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20
Q

How does liver/kidney disease affect thyroid hormone T1/2?

A

Decrease in plasma protein levels –> decreases T1/2

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21
Q

____% of T4 –> T3

A

30 - 40%

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22
Q

____% of T4 –> rT3

A

50%

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23
Q

How are the conjugates of the hormones excreted from the body?

A

Conjugates enter bile –> gut –> feces

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24
Q

What are the 3 enzymes involved in deiodination?

A
  1. Type 1 deiodinase
  2. Type 2 deiodinase
  3. Type 3 deiodinase
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25
Q

Which of the thyroid hormones are formed by Type 1 deiodinase?

A

T3 and rT3

26
Q

Which of the thyroid hormones are formed by Type 2 deiodinase?

A

T3

27
Q

Which of the thyroid hormones are formed by Type 3 deiodinase?

A

rT3

28
Q

Where is Type 1 deiodinase found?

A

Liver and kidney

29
Q

Where is Type 2 deiodinase found?

A

Brain (pituitary) and brown fat

30
Q

Where is Type 3 deiodinase found?

A

Brain and placenta

31
Q

Rate of T4 –> T3 increases or decreases with hypothyroidism?

A

Increases

32
Q

Rate of T4 –> T3 increases or decreases with hyperthyroidism?

A

Decreases

33
Q

____, a glycoprotein hormone, stimulates all steps involved in T4 synthesis.

A

TSH

34
Q

TSH receptors are coupled to Gs, leading to ____ ____.

A

cAMP formation

35
Q

cAMP –> ____ –> ____ –> increased protein

A

cAMP –> PKA-CREB –> increased mRNA –> increased protein

36
Q

____ is needed for synthesis.

A

Iodide

37
Q

T3 is ___ - ___ times as active as T4.

A

3 - 5X

38
Q

What are the 3 main components of thyroid hormone’s calorigenic actions?

A
  1. Increased heat generation
  2. Increased O2 consumption
  3. Increased basal metabolic rate
39
Q

Where is brown fat found within the body?

A

Between scapulas

Thorax

Abdomen

40
Q

Brown fat cells contain large numbers of what?

A

Mitochondria

41
Q

Brown fat cells contain large numbers of mitochondria with ____ ____ to generate heat.

A

Uncoupling proteins

42
Q

Complete the pathway: Cold body temperature –> _____ –> ______ –> Increased T4

A

Cold body temperature –> Increased TRH –> Increased TSH –> Increased T4

43
Q

Complete the pathway: Cold body temperature –> _____ –> ______ –> Increased T3 –> Increased thermogenin in mitochondria

A

Cold body temperature –> Increased Epi, NE –> Increased type II deiodinase –> increase T3 –> Increased thermogenin in mitochondria

44
Q

What are the 4 cardiovascular effects of thyroid hormone?

A
  1. Increased CO
  2. Increased O2 consumption
  3. Increased expression of alpha-1 and beta receptors
  4. Increased expression of alpha-myosin heavy chain and Ca2+ channels in the myocardium
45
Q

Would you expect a high or low cholesterol level in a hypothyroid patient? Why?

A

High cholesterol - thyroid hormones increase the conversion of cholesterol into bile acids

46
Q

Thyroid hormone is needed for skin and hair turnover. What would be the dermatologic effects of hyperthyroidism?

A

Alopecia

47
Q

Thyroid hormone is needed for skin and hair turnover. What would be the dermatologic effects of hypothyroidism?

A

Thickened skin (myxedema)

48
Q

What is the effect of thyroid hormones on GH secretion?

A

Increases GH secretion & action

49
Q

Thyroid hormones are critical for the development and maintenance of _____ tissue.

A

Neural

50
Q

In which tissues do you see calorigenesis due to thyroid hormones?

A
  1. Heart
  2. Skeletal muscle
  3. Liver
  4. Kidney
51
Q

Where is irisin found?

A

Within the skeletal muscle

52
Q

What is the function of irisin?

A

Converts white fat cells (FCs) into brown fat cells (BFCs)

53
Q

How would hypothyroidism affect keratin and sebum production?

A

Both would be increased

54
Q

What are the neuromuscular effects of thyroid hormones?

A

Increase synthesis of proteins associated with neuromuscular activity

55
Q

What are the neuromuscular consequences of hypothyroidism?

A
  1. Myopathy
  2. Cranial nerve VII paralysis
  3. Cranial nerve VIII paralysis
  4. CNS depression
56
Q

What is the MOA of methimazole?

A

Blocks iodination and coupling reactions

57
Q

Methimazole is 10x more potent than what?

A

Propylthiouracil (PTU)

58
Q

Which of the following causes hemolytic anemia: Methimazole or Propylthiouracil?

A

Propylthiouracil (PTU)

59
Q

Which of the following has less side effects: PTU or Methimazole?

A

Methimazole

60
Q

What are the advantages of topical Methimazole?

A
  1. Convenience

2. Less GI disturbance (4%)

61
Q

What are the disadvantages of topical Methimazole?

A
  1. Human hazard

2. Inconsistent absorption

62
Q

What is the half-life of sodium idodide 131?

A

8 days

pharmacology (21 decks)

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