Hypothyroidism

Question 1

What is the most common cause of hypothyroidism in dogs?

Answer 1

lymphocytic thyroiditis

• autoimmune disease!

Question 2

What is the most common cause of misdiagnosis of hypothyroidism?

Answer 2

euthyroid sick syndrome - suppressed hypothalamic-pituitary stimulation of thyroid due to illness

Question 3

What are the most important physiological effects of thyroid hormones?

Answer 3

increase:

• metabolic rate
• oxygen consumption
• heart rate
• erythropoiesis
• catecholamine release
• catabolism of muscle and adipose tissue

Question 4

What mineral is incorporated into thyroid hormones?

Answer 4

iodine

Question 5

What are the 3 most common clinical signs of hypothyroidism? What else can be seen?

Answer 5

1. weight gain / obesity
2. lethargy
3. bilaterally symmetric alopecia over the lateral trunk, tail, and ventral thorax

pyoderma, hyperkeratosis, seborrhea, hyperpigmentation, bradycardia, weak pulses, low voltage ECG complexes

Question 6

What 2 abnormalities are seen on routine bloodwork and diagnostics in hypothyroid patients?

Answer 6

1. mild non-regenerative anemia
2. hypercholesterolemia

Question 7

What is the preferred screening test for hypothyroidism? What 3 tests are used for confirmation?

Answer 7

serum total T4 levels

1. cTSH and free T4 by equilibrium dialysis –> increased cTSH, low fT4
2. TSH stimulation test –> low T4
3. trial of T4 replacement

Question 8

How is hypothyroidism treated?

Answer 8

oral administration of levothyroxine

• optimal dosing varies among dogs and T4 levels should be evaluated after beginning therapy and while treatment is maintained
• dose calculated based on dog’s ideal body weight