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RUSVM SAM 1 > Hyper/hypo Thyroid > Flashcards

Hyper/hypo Thyroid Flashcards

1
Q

What is the active form to thyroid hormone?

A

T3

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2
Q

Which has a stronger effect, T3 or T4?

A

T3

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3
Q

What is the the normal role of thyroid hormone

A

Maintain metabolic rate and O2 consumption

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4
Q

The most common form of hypothyroidism is ???

A

Primary (95%)

  • lymphocytic thyroiditis
  • idiopathic atrophy
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5
Q

What are other causes of a low T4 that is not hypothyroidism

A

Iatrogenic
Euthyroid sick syndrome
Drug therapy

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6
Q

Thyroidectomy is an example of what type of hypothyroidism

A

Iatrogenic

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7
Q

What drug therapies can cause a low T4?

A

Glucocorticoids
Carprofen (NSAID)
Furosemide
Phenobarbital /sulfas

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8
Q

That is the usual signalment of a primary hypothyroid animal?

A

Middle age
Medium to large breed dog

Some inherited breeds - OFA registry

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9
Q

General appearance of a hypothyroid dog?

A

Lethargic
Alopecia
Hyperpigmentation

Rat tail
Seborrhea
Hypothyroid myedema

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10
Q

What is myxedema?

A

Facial appearance

Deposition of mucopolysacchharides in the dermis

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11
Q

Is myxedema associated with hyperthyroid or hypothyroidism?

A

HYPOthyroidism

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12
Q

You have hypothyroidism on your differential list, what should you do next to confirm?

A

CBC -> low anemia

Serum biochem -> low levels of T4 (this can also indicated euthyroid sick)

UA

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13
Q

Your patient has a history, PE, and lab work with a low T4, you would likely submit what test to confirm hypothyroidism?

A

TSH

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14
Q

Is it appropriate to treat a presumptive diagnosis with low T4 and normal TSH for hypothryoidism, if so, what would you use?

A

Yes you can treat or retest later

Levothyroxine

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15
Q

If there is a low normal T$ and you really think it is hypothyroidism, what do you do? What is there is a high T4?

A

FT4 by eqd.

FT4 by eqd and measure for anti-T4 autoantibodies

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16
Q

In a TSH stimulation test, you see a significant increase in the post-T4 value. How do you interpret ?

A

Normal

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17
Q

In a TSH stimulation, you see no significant increase in post T4 levels. What is your interpretation?

A

Hypothyroid dog

Due to thyroid gland atrophy or destruction

18
Q

What is the timeline of resolvment of clinical signs for hypothyroid cases?

A

2wks- improvement in attitude

6wks-improvement in derm signs

3months- hair regrowth

19
Q

What is the etiology of excessive production of T4 and T3

A

Functional tumor (adenoma is most common)

70% of cats with hyperthyroidism have bilateral tumors

20
Q

What is the signalment for hyperthyroid cases?

A

Most common endocrinopathy of other cats

Mean age= 12yrs

21
Q

Clinical signs of hyperthyroidism?

A

Weight loss, unkempt “scraggly” coat

PU/PD -> osmotic diuretics, and renal medullary washout, psychogenic or concurrent RF

Vomiting -> gastric distention/overeating
Diarrhea -> osmotic (increase fat intake), hypermotility

22
Q

What is apathetic hyperthyroidism ??

A

Weight loss with poor appetite

Decreased activity, lethargy

23
Q

Cat with..
weight loss and scraggly coat
PU/PD
Vomiting

CBC shows stress leukogram with erythrocytosis
Biochem shows increase ALk phos and ALT
UA- isosthenuric
T4- high

A

Hyperthyroidism

24
Q

What should you do if T4 levels are normal but you still suspect hyperthyroidism?

A

Repeat T4 in a few days or weeks

OR

Submit a FT4 by eqd if T4 is mid to high normal range

25
Q

Can we just check FT4 to confirm hyperthyroidism in a cat?

A

Nope

FT4 is often high in euthyroid sick syndrome

26
Q

What other tests are possible for tough hyperthyroid cases?

A

T3 suppression test

27
Q

What additional diagnostic work-up can be done in hyperthyroid cases

A

BP

  • fundic exam
  • UPC/urine culture (protein loss)

Cardiac evaluation

  • ECG
  • Radiographs
  • Echocardiography

Nuclear scintigraphy -> radioactive iodine

28
Q

What are the 4 treatment options for hyperthyroidism? Which are reversible?

A

Medical, dietary, surgical, or radioactive iodine

Medical and dietary are reversible

Surgical and radioactive iodine are not reversible

29
Q

T/F: the best line of treatment for hyperthyroidism is to treat with radioactive iodine first to decrease T4 production

A

FLASE

Hyperthyroidism can often mask renal failure.. in this even you would not want to purpose long term solutions like surgery or radioactive iodine

First line should be 30days of methimazole where you check renal function after

30
Q

How does hyperthyroid mask renal disease?

A

Increase in BP -> increase GFR

31
Q

What are some important considerations to be considered in surgical treatment of hyperthyroid?

A

Pro- can be a long term solution

Con

  • surgery is close to many major vessels
  • removal of too much-> iatrogenic hypothryoidism
  • accidental removal of parathyroid
32
Q

How does I-131 treat hyperthyroidism

A

Tumor concentrates the radioactive iodine -> emitting beta particles that are locally destructive

33
Q

What is the MOA of methimazole?

A

Inhibits thyroid hormone synthesis by blocking incorporation of iodine

34
Q

What are some side effects of methimazole?

A

Vomiting (anorexia)

Liver, marrow, and skin(excoriation) reactions

35
Q

Why would transdermal methimazole be a good choice for hyperthyroid cats?

A

Some cats difficult to manage with oral meds

Give transdermal because of vomiting

36
Q

What is the prognosis for hyperthyroidism?

A

Good

*be sure to monitor renal parameter and T4 with all treatments

37
Q

What is the most common thyroid tumor in dogs?

A

Malignant (90%)

-usually highly invasive and non-functional

38
Q

Middle aged to older dog

PE:
Cervical mass on palpation

DDX:

A

Neoplasia.
-Thyroid tumor, lymphoid, parathyroid, lipoma, sarcoma

Inflammatory
-abscess, foreign body, fungal, granuloma

Cystic
-non-inflammatory lesion of thyroid, parathyroid, salivary mucocele

39
Q

What is your diagnostic plan for a dog with a cervical mass?

A

Evaluate mass

FNA: thyroid tumors are highly vascular -> mostly blood

Excisional biopsy

Nuclear imaging

Labwork
Metastasis check

40
Q

What is the treatment for a canine thyroid tumor?

A

Surgery: palliative, debulk

Cobalt irradiation after debulking

Chemotherapy

Radioactive iodine (only for functional tumors)

RUSVM SAM 1 (26 decks)

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