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Vet Derm Review > Endocrinology - NAVDF 2021 > Flashcards

Endocrinology - NAVDF 2021 Flashcards

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1
Q

T/F: Most cases of canine hypothryroidism are primary hypothyroidism.

A

True - a result of dysfunction of the thyroid gland itself

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2
Q

T/F: Lymphocytic thyroiditis is a slowly progressive disease and clinical signs of hypothyroidism will not be present until at least 75% of the function of the thyroid gland is lost.

A

TRUE

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3
Q

What breeds are at increased risk for hypothyroidism based on their dog leukocyte antigen haplotype?

A

Doberman pinscher, Giant Schnauzer, Rhodesian ridgeback, English setter

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4
Q

What are possible causes of primary hypothyroidism?

A

lymphocytic thyroiditis, idiopathic atrophy of the thyroid gland, neoplasia, iodine deficiency, congenital hypothyroidism, radioactive iodine treatment, drugs (potentiated sulfonamides, corticosteroids, phenobarbital, some NSAIDs)

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5
Q

Secondary hypothyroidism results from a dysfunction of what?

A

pituitary gland (decreased thyrotropin/TSH production) dysfunction leading to secondary follicular thyroid atrophy

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6
Q

What are possible causes of secondary hypothyroidism?

A

pituitary tumors, congenital pituitary malformations (cystic Rathke’s pouch), pituitary trauma/surgery

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7
Q

Tertiary hypothyroidism results from a dysfunction of what?

A

hypothalamus dysfunction (decreased thyrotropin-releasing hormone)

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8
Q

What results in decreased TSH secretion (provides negative feedback for TSH secretion)?

A

thyroid hormones (thyroxine/T4; 3,5,3’-triiodothyronine/T3), somatostatin, dopamine, catecholamine, TNF-alpha, some interleukins

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9
Q

Why do dogs have lower serum total thyroxine/T4 levels than humans?

A

dogs have weaker protein binding of T4 – lower serum total T4 levels and higher free T4 levels

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10
Q

T/F: Thyroxine must undergo deiodination to T3 to be able to bind to the cell’s nuclear thyroid receptor.

A

True - although T4 has some intrinsic activity, it is often considered a prohormone as it has to be deiodinated to T3 to exert the metabolic effects of thyroid hormone

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11
Q

What is reverse T3?

A

metabolically inactive form of T3 - 3,3’,5’-triiodothyronine; this deiodination pathway increases during periods of non-thyroidal illness

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12
Q

Why is alopecia seen in hypothyroidism in areas of wear/tear?

A

thyroid hormones are very important to the skin and promote the initiation of the anagen phase of the hair follicle cycle

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13
Q

What dogs can have lower T4 concentrations?

A

older dogs and sight hounds (of any age)

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14
Q

Why is serum T3 not useful in making a diagnosis of primary hypothyroidism?

A

although T3 is the most important biologically active thyroid hormone at a cellular level, a large portion of it is produced by deiodination in peripheral tissues

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15
Q

T/F: Endogenous canine TSH is consistently increased in canine hypothyroidism.

A

False - up to 38% of hypothyroid dogs may have a cTSH concentration within the reference range; has a low sensitivity but a good specificity

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16
Q

What is the sensitivity and specificity of free T4 and endogenous TSH serum concentration for diagnosis of primary hypothyroidism?

A

sensitivity of 74-80%, specificity of 98% (overall accuracy of 86%)

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17
Q

Animals with lymphocytic thyroiditis can have antibodies to what components?

A

thyroglobulin (59% of hypothyroid dogs), T4, T3

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18
Q

What should be done if a dog has a positive anti-thyroglobulin antibody but normal thyroid function?

A

monitor for future development of hypothyroidism

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19
Q

What is more common: antibodies to T3 or T4?

A

anti-T3 antibodies

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20
Q

Why might an animal with true primary hypothyroidism have a normal serum T3 or T4?

A

anti-T3 and anti-T4 antibodies can interfere with some assays to measure T3 or T4, resulting in an erroneously high value

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21
Q

Glucocorticoids: effect on total T4? Free T4? Endogenous TSH?

A

decreased or no change; decreased or no change; no change or decreased (all changes are dose and duration-dependent)

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22
Q

Phenobarbital: effect on total T4? Free T4? Endogenous TSH?

A

decreased or no change; decreased or no change; no change or decreased

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23
Q

Sulfonamides: effect on total T4? Free T4? Endogenous TSH?

A

decreased; decreased; increased

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24
Q

Potassium bromide: effect on total T4? Free T4? Endogenous TSH?

A

no change; no change; no change

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25
Q

Clomipramine: effect on total T4? Free T4? Endogenous TSH?

A

decreased; decreased; no change

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26
Q

Aspirin: effect on total T4? Free T4? Endogenous TSH?

A

decreased; no change; no change

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27
Q

Ketoprofen: effect on total T4? Free T4? Endogenous TSH?

A

decreased; no change; no change

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28
Q

Carprofen: effect on total T4? Free T4? Endogenous TSH?

A

decreased or no change; decreased or no change; decreased or no change

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29
Q

Non-thyroidal illness: effect on total T4? Free T4? Endogenous TSH?

A

decreased; decreased or no change; no change or increased (slight)

30
Q

T/F: Thyroid supplementation may cause hair regrowth in an animal with non-thyroidal illness.

A

True - thyroid hormone therapy is a signal for hair follicles to initiate anagen

31
Q

How long should thyroid supplementation be decreased before evaluating thyroid function?

A

6-8 weeks

32
Q

Why can progesterone-secreting adrenal tumors result in an increase in unbound cortisol?

A

progesterone is a glucocorticoid agonist and competes with cortisol for binding (increase in progesterone can cause an increase in cortisol)

33
Q

What part of the adrenal gland makes cortisol?

A

zona fasciculata

34
Q

Pituitary tumors may secrete what other hormones besides ACTH?

A

growth hormone, melanocyte stimulating hormone

35
Q

What does the hypothalamus produce to regulate cortisol production?

A

corticotropin-releasing hormone (delivered to the pituitary gland –> stimulates secretion of ACTH)

36
Q

What stimulates the hypothalamus to secrete corticotropin-releasing hormone?

A

cytokines (IL-1, IL-6, TNF-alpha) and/or hormones (leptin, dopamine, angiotensin II, antidiuretic hormone)

37
Q

What are the components of pro-opiomelanocorticin (POMC)?

A

ACTH, melanocyte-stimulating hormone

38
Q

What inhibits release of corticotropin-releasing hormone from the hypothalamus?

A

glucocorticoids and somatostatin

39
Q

What does the pars intermedia of the pituitary produce?

A

alpha-MSH and corticotropin-like intermediate peptide; pro-opiomelanocorticin (cleaved to ACTH and beta-LPH)

40
Q

What does the posterior pituitary produce? (neurohypophysis)

A

antidiuretic hormone, oxytocin

41
Q

What stimulates ACTH production from pituitary gland?

A

corticotropin-releasing hormone; stress & hypoglycemia

42
Q

What inhibits release of ACTH from the pituitary gland?

A

cortisol, glucocorticoids

43
Q

Why can’t the zona glomerulosa produce cortisol or androgens?

A

lacks 17-alpha-hydroxylase

44
Q

The enzyme 17-alpha-hydroxylase is required to synthesize what products?

A

17-hydroxy-pregnenolone and 17-hydroxy-progesterone (precursors to cortisol and androgens)

45
Q

Why are urinary tract infections common with hypercortisolemia?

A

immunosuppressive effects of hypercortisolemia and because dilute urine is less bactericidal

46
Q

Other than the dog, what is the only other species to develop calcinosis cutis with hypercortisolism?

A

chinchilla

47
Q

Acquired skin fragility in cats is associated with what conditions?

A

hyperadrenocorticism, iatrogenic hypercortisolemia, excessive levels of progestational compounds from either adrenal tumors or iatrogenic effect of administered progestational compounds

48
Q

T/F: Elevated ALP is seen in both the cat and dog secondary to hyperadrenocorticism.

A

False - the cat does NOT have a steroid-induced isoenzyme of ALP

49
Q

Why is the ACTH stimulation test the test of choice for identifying iatrogenic hyperglucocorticoidism?

A

evaluates adrenal cortex reserve – iatrogenic HAC causes adrenocortical atrophy and failure to respond to ACTH stimulation

50
Q

T/F: Dogs with an adrenal tumor will have lower than normal endogenous ACTH plasma levels.

A

True - most of the time

51
Q

What effect does hyper thyroidism have on adrenal gland size in cats?

A

can increase adrenal glands by as much as 20%

52
Q

What enzyme does trilostane inhibit?

A

3-beta-hydroxysteroid dehydrogenase: enzyme needed to convert pregnenolone and 17-alpha-hydroxypregnolone to progesterone and 17-alpha-hydroxyprogesterone (precursors in cortisol synthesis)

53
Q

T/F: Mitotane is fat-soluble and needs to be administered with a meal.

A

TRUE

54
Q

What mineral is present in lesions of calcinsosis cutis?

A

apatite

55
Q

What is a proposed pathomechanism for PU/PD seen in hyperadrenocorticism in dogs?

A

increased GFR due to vascular volume and renal blood flow (mineralocorticoid effects), inhibits responsiveness to ADH in dogs –> decreased renal tubular resorption of H20 –> poyluria and compensatory polydipsia

56
Q

Which is more effective for treatment of hyperadrenocorticism in cats: mitotane or trilostane?

A

trilostane – mitotane does NOT control clinical signs

57
Q

What is the definition of a paraneoplastic syndrome?

A

disease or clinical signs that develop distant from the site of a tumor, caused by the presence of the tumor or its metastasis, but is not resulting from the local presence of neoplastic cells

58
Q

Paraneoplastic syndromes are mediated by what?

A

hormones, cytokines, growth factors released by tumors or by an immune response targeted against the tumor

59
Q

Mutations in the gene BHD that encodes for folliculin can result in what tumor type in intact female dogs?

A

uterine leiomyomas

60
Q

Skin lesions are most commonly associated with what systemic mycosis in dogs? Cats?

A

Dogs - blastomycosis, Cats - cryptococcus

61
Q

What viral infections in dogs can cause cutaneous signs?

A

canine distemper and pseudorabies (and papillomavirus)

62
Q

What viral infections in cats can cause cutaneous signs?

A

FeLV, FIV, FHV, feline calicivirus, feline coronavirus (FIP), papillomavirus

63
Q

Where are the highest concentrations of zinc found?

A

keratinized tissue of the nasal planum, tongue, and footpad

64
Q

Zinc Responsive Dermatosis Syndrome II typically occurs in rapidly growing puppies fed poor quality dog food or over-supplemented with what?

A

calcium – can bind to zinc

65
Q

Superficial necrolytic dermatitis has been reported in what species?

A

dog, cat, and black rhinoceros

66
Q

Clinical signs of superficial necrolytic dermatitis?

A

footpads develop marked crusting, fissuring, and ulcerations; erythema, crusting, exudation, ulceration and alopecia can also involve the periocular or perioral regions, pressure points on the limbs and scrotum

67
Q

What are non-immunopathogenic mechanisms that result in vasculitis?

A

processes that weaken the integrity of the vascular wall - invasion of neoplastic cells or microbial agents, influences of burns, trauma, endotoxin, or hemodynamic factors

68
Q

What are immunopathogenic mechanisms that result in vasculitis?

A

deposition of immune complexes, antibodies directed against vascular wall components, anti-neutrophilic antibody-mediated vessel damage, cytotoxic T cells directed against vascular components and cytokine induced mechanisms

69
Q

What are the histopathologic findings with feline paraneoplastic alopecia?

A

follicular atrophy with miniaturization of hair follicles; epidermal hyperplasia

70
Q

How are the nutritional needs of chronic hepatitis and superficial necrolytic dermatitis different?

A

with chronic hepatitis, you want to restrict protein; with SND, you need to INCREASE protein

71
Q

What is thought to cause the hypoaminoacidemia in superficial necrolytic dermatitis?

A

increased hepatic catabolism of amino acids – reason that IV amino acid infusions work is that they bypass the liver

72
Q

When an erythemic skin lesion blanches on diascopy what does that mean caused the erythema?

A

increased blood flow to the area (different from non-blanching => vascular compromise)

Vet Derm Review (44 decks)

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