Bryan - Sa Med - Thyroid And Parathyroid Disorders - Fall 3Rd Yr

Front 1

How does low iodine affect the thyroid? High iodine?

Back 1

Low levels = more T3 produced
High levels = decreased synthesis

Front 2

Hyperthyroidism is to ________ as __________ is to dogs.

Back 2

Hyperthyroidism is to _CATS_ as _HYPOTHYROIDISM_ is to dogs.

Front 3

What is the most common type of hyperthyroidism seen in cats? In dogs?

Back 3

Cats (multinodular adenoma or adenoma)
Dogs (Thyroid carcinoma)

Front 4

What is the common signalment for an animal with hyperthyroidism?

Back 4

Older (>8y) cat

Front 5

What are the major clinical signs associated with hyperthyroidism?

Back 5

Weight loss + Polyphagia
PU/PD
Behavioral changes
GI signs (diarrhea/vomiting/bulky stool)
Dermatologic signs
lots of others...

Front 6

Why does hyperthyroidism cause PU/PD?

Back 6

Increased renal blood flow = increased GFR

Front 7

T or F:
Decreased appetite, severe weight loss, and muscle wasting can be congruent with hyperthyroidism.

Back 7

True!
Apathetic hyperthyroidism can present like this!

Front 8

T or F:
A palpable thyroid in a BAR cat is not a good indicator of hyperthyroidism.

Back 8

True!
This is pretty sensitive but not specific.

Front 9

How does hyperthyroidism cause thyrotropic cardiomyopathy?

Back 9

T3/T4 increases beta 1 receptor number and affinity on the heart

Front 10

Which of the following are NOT common clin path findings in a hyperthyroid cat?
a) mild non-regenerative anemia
b) ABSENCE of azotemia
c) increased serum fructosamine
d) systemic hypertension
e) steatorrhea and hypercholesteremia

Back 10

a) mild non-regenerative anemia (should be polycythemia)
c) increased serum fructosamine (should be DECREASED)
e) steatorrhea and hypercholesteremia (should be HYPOcholesteremia)

Front 11

What would be expected on radiography of a hyperthyroid cat?

Back 11

Cardiomegaly

Front 12

What is commonly used as a screening test for hyperthyroidism?

Back 12

Total T4

Front 13

Why is free T4 not as good of a screening test even though it has a higher sensitivity than total T4?

Back 13

Euthyroid sick syndrome can falsely elevate free T4.

Front 14

What are diagnostic options if TT4 and free T4 tests are non-diagnostic?

Back 14

T3 suppression test
TRH stim test
Radionuclide imaging

Front 15

How is the T3 suppression test administered and interpreted?

Back 15

Give T3 (7 doses over 3 days)
In a normal cat, this will SUPPRESS thyroid hormone production.

Front 16

How is the TRH stim test adminestered and interpreted?

Back 16

Administer TRH via IV and measure TT4 4 hrs later.
Normal cat TT4 should increase 2x above baseline; hyperthyroid cats stimulate <50% above baseline.

Front 17

What is the normal intensity ratio of the thyroid to the salivary glands when performing radionuclide imaging?

Back 17

1:1 ratio

Front 18

What are medical treatment options for hyperthyroidism?

Back 18

Methimazole (oral and topical)
Carbimazole (in Europe)

Front 19

What are some contraindications to hyperthyroid surgery?

Back 19

Cats w/abnormal GFR

Front 20

What are severe reactions indicating immediate withdrawal of methimazole?

Back 20

Facial excoriation
Blood dyscrasias
Hepatopathy

Front 21

What are complications to thyroidectomy?

Back 21

Lar par
Horner's
Hypoparathyroidism

Front 22

Why does radioactive iodine therapy not kill all the thyroid tissue?

Back 22

Only acts on ACTIVE portions of the thyroid (kills the cancer and not the healthy cells)

Front 23

T or F:
Most hyperthyroid patients treated by radioactive iodine require retreatment.

Back 23

True! in about 5 years...

Front 24

Choose the false statement regarding canine hyperthyroidism:
a) is a rare and chronic form of thyroid carcinoma
b) usually presents with normal lab values
c) has 40% metastasis to the thorax
d) has a great prognosis when encapsulated and no metastasis

Back 24

a) is a rare and chronic form of thyroid carcinoma is FALSE - canine hyperthyroidism is usually an ACUTE process

Front 25

What effect does thyroid hormone have on lipid metabolism?

Back 25

enhanced utilization of lipid substrates
increased synthesis & mobilization of triglycerides
increased non-esterified FAs
increased lipoprotein lipase activity

Front 26

What is the major cause of primary hypoparathyroidism?
a) no TSH released from the pituitary
b) lymphoplasmacytic thyroiditis
c) neoplasia
d) idiopathic atrophy

Back 26

pretty much 50/50 between b and d
b) lymphoplasmacytic thyroiditis
d) idiopathic atrophy (end result of autoimmune)

Front 27

What is the common signalment for hypothyroidism?

Back 27

2-6yo dog (golden, lab, dobie)

Front 28

What are the most common signs associated with hypothyroidism?

Back 28

Gain in body weight
Lethargy
Dermatologic issues
Heat-seeking
Mental changes

Front 29

Why do hypothyroid dogs have a thin hair coat?

Back 29

Hair follicles undergo telogen arrest

Front 30

Which of the following are common signs for hypothyroidism in dogs?
a) bradycardia
b) constipation
c) weakness
d) oligospermia

Back 30

c) weakness; the rest are UNCOMMON signs

Front 31

What ocular signs can be present in hypothyroidism and what is the pathophysiology?

Back 31

Corneal lipid deposits, corneal ulceration, uveitis (hypercholesteremia/lipidemia deposits in eyes)

Front 32

Which of the following are NOT signs consistent with hypothyroidism?
a) polycythemia
b) schistocytes
c) increased ALT and ALP
d) USG normal

Back 32

a) polycythemia (should be non-regen anemia)
b) schistocytes (should be target cells)

Front 33

A BAR greyhound tests low on a TT4 test. What is your next step?

Back 33

No further followup - no clinical signs + sight hounds are normally low thyroid anyway

Front 34

What are normal ranges of TT4? Hypothyroid ranges?

Back 34

Normal (1 - 3.3)
Hypo (0 - 1.5)

Front 35

If you suspect autoantibodies as an etiology for hypothyroid, what test should you use?

Back 35

free T4

Front 36

Which test is useful in diagnosing primary hypothyroidism? How is it interpreted?

Back 36

Baseline TSH (high baseline TSH + low T4 or fT4 = hypothyroid)

Front 37

What drugs can interfere with hypothyroid testing?

Back 37

Steroids
Phenobarbital
Sulfonamides
Mitotane

Front 38

How is hypothyroid treated? How is this treatment monitored?

Back 38

Hormone supplementation (levothyroxine); monitor with TT4 + TSH baseline 4-6 hrs post administration

Front 39

What is the prognosis for hypothyroidism?

Back 39

If primary = good
if secondary or congenital = poor to guarded

Front 40

What is the most common cause of feline hypothyroidism?

Back 40

Iatrogenic (thyroidectomy or I-131)

Front 41

What are the 2 axes regulating calcium in the body?

Back 41

Parathyroid axis
Vitamin D axis

Front 42

Which of the following statements is true?
a) 50% of calcium in the body is ionized
b) 50% of serum calcium is albumin bound
c) 1% of body calcium is found in the serum
d) Most calcium in the body is bound to albumin or anion

Back 42

c) 1% of body calcium is found in the serum

Remember 99% TOTAL in bone, 1% of TOTAL in serum;
(in serum, 50% ionized, 40% w/albumin, 10% anion-bound)

Front 43

Where does PTH have its effects and what is the net result of these effects?

Back 43

Bone, Kidney, and GI
(net result = increased serum Ca)

Front 44

What specific effects does PTH have on bone?

Back 44

Increases osteoclast resorption leading to increased Ca and PO4

Front 45

What specific effects does PTH have on the kidneys?

Back 45

Decreases Ca excretion; increases Ca resorption; increases P excretion; activates vitamin D

Front 46

What specific effects does PTH have on the GI tract?

Back 46

Increases Ca and P absorption (via vitamin D)

Front 47

What hormones are involved in the parathyroid axis?

Back 47

PTH
Calcitonin

Front 48

What action does calcitonin have on the bone? The kidney? What is the net result?

Back 48

Stops osteoclast activity.
Inhibits P reabsorption.
Net = decreases serum Ca and P

Front 49

What are some infectious causes of hypercalcemia?

Back 49

Granulomatous diseases (histo, blasto, asper, coccidiodio, and schistosomiasis)

Front 50

What are some differentials for hypercalcemia? Which is the most important in small animals?

Back 50

NEOPLASIA (most important)
Spurious (lab error)
Granulomatous dz
Hyperparathyroidism (primary and secondary renal)
Hypoadrenocorticism
Renal failure
Nutritional secondary hyperparathyroidism
Vitamin D toxicosis

Front 51

Which neoplasms can commonly lead to hypercalcemia?

Back 51

Lymphoma
Anal sac adenocarcinoma
Multiple myeloma

Front 52

Why does renal failure cause hypercalcemia?

Back 52

Reduced GFR = reduced P excretion and secondary hyper PTH
Low renal mass = less vitamin D = less Ca absorption from GI = parathyroid hyperplasia

Front 53

Which pharmaceuticals cause iatrogenic hypercalcemia?

Back 53

Prednisolone or other glucocorticoids

Front 54

What is the common signalment for an animal with primary hyperparathyroidism?

Back 54

Older dog (maybe a Keeshond)

Front 55

What are common clinical signs with primary hyperparathyroidism in dogs?

Back 55

PU/PD
Muscle weakness & lethargy
(sometimes vomiting, diarrhea, constipation, lower UTI signs)

Front 56

What are common clinical signs with primary hyperparathyroidism in cats?

Back 56

anorexia, lethargy, and vomiting

Front 57

What lab values are commonly seen with primary hyperparathyroidism?

Back 57

High Ca (total and ionized)
Low P
Azotemia (generally)

Front 58

Predict the following relative values in primary hyperparathyroidism.
a) PTH
b) PTHrp
c) Total Ca
d) Ionized Ca
e) P
f) vitamin D

Back 58

a) PTH (HIGH)
b) PTHrp (LOW)
c) Total Ca (HIGH)
d) Ionized Ca (HIGH)
e) P (Normal to LOW)
f) vitamin D (normal to HIGH)

Front 59

Predict the following relative values in chronic renal failure.
a) PTH
b) PTHrp
c) Total Ca
d) Ionized Ca
e) P
f) vitamin D

Back 59

a) PTH (HIGH to normal)
b) PTHrp (LOW to normal)
c) Total Ca (HIGH to normal)
d) Ionized Ca (Normal to LOW)
e) P (HIGH to normal)
f) vitamin D (LOW)

Front 60

Predict the following relative values in nutritional secondary hyperparathyroidism.
a) PTH
b) PTHrp
c) Total Ca
d) Ionized Ca
e) P
f) vitamin D

Back 60

a) PTH (HIGH)
b) PTHrp (LOW)
c) Total Ca (Normal)
d) Ionized Ca (Normal)
e) P (Normal)
f) vitamin D (LOW)

Front 61

Predict the following relative values in hypervitaminosis D.
a) PTH
b) PTHrp
c) Total Ca
d) Ionized Ca
e) P
f) vitamin D

Back 61

a) PTH (LOW)
b) PTHrp (LOW)
c) Total Ca (HIGH to normal)
d) Ionized Ca (HIGH to normal)
e) P (HIGH to normal)
f) vitamin D (HIGH)

Front 62

Predict the following relative values in neoplasia.
a) PTH
b) PTHrp
c) Total Ca
d) Ionized Ca
e) P
f) vitamin D

Back 62

a) PTH (LOW)
b) PTHrp (HIGH)
c) Total Ca (HIGH)
d) Ionized Ca (HIGH)
e) P (LOW)
f) vitamin D (LOW to HIGH)

Front 63

How is primary hyperparathyroidism diagnosed?

Back 63

Run PTH and PTHrp; maybe ultrasound or radiography

Front 64

How is primary hyperparathyroidism treated medically?

Back 64

Correct dehydration (saline)
Diuretics (Furosemide)
Glucocorticoids
Bisphosphonates
Maybe calcitonin

Front 65

What are non-surgical options for correcting primary hyperparathyroidism?

Back 65

Percutaneous ethanol
Heat radifrequency ablation

Front 66

At what level can clinical signs of hypocalcemia be seen?
a) <2.3 iCa
b) <12 tCa
c) <1.1 iCa
d) <9 tCa

Back 66

c) <1.1 iCa
d) <9 tCa

Front 67

Tetany is seen when total Ca drops below ________.

Back 67

below 6!

Front 68

What are major differentials for hypocalcemia?

Back 68

HYPOALBUMINEMIA
Lab error
Iatrogenic
Chronic/Acute Renal Failure
Intestinal malabsorption

Front 69

What is the major cause for primary hypoparathyroidism?

Back 69

Iatrogenic (surgery)!!!
Major NATURAL cause is dysgenesis or lymphocytic parathyroiditis

Front 70

What is the common signalment for naturally occurring primary hypoparathyroidism?

Back 70

5yo female cats

Front 71

What are common lab values for primary hypoparathyroidism?

Back 71

hypocalcemia
hyperphosphatemia
Low or low normal PTH

Front 72

How is hypo-PTH treated?

Back 72

Acute (Ca gluconate + diazepam)
Managemen (Vitamin D + Ca supplementation)