Hypothyroidism

Question 1

hypothyroidism - causes

Answer 1

mostly in dogs
congenital abnormality or more commonly as an acquired disorder
congenital due to enzyme deficiencies, acquired due to immune-mediated destruction of the thyroid tissue
almost never a problem because of problems with pituitary function

Question 2

clinical signs

Answer 2

Lethargic and disinterested
Maybe overweight - Can be exercise intolerant and have muscle or joint pain
Dermal changes of alopecia and hyperpigmentation with thickened skin
Infertility in males and females
Occasionally neurological problems

Question 3

clinical pathology

Answer 3

Typically a mild non-regenerative anemia
Around 60% will have an elevated serum cholesterol
Around 40% will have an elevated serum creatinine kinase
Proteinuria not uncommon
fairly non-specific

Question 4

diagnostic tests

Answer 4

basal total T4 
basal free T4 - usually low
basal TSH 
TRH response test 
TSH response test 
thyroglobulin autoantibodies

Question 5

problems with the diagnostic tests

Answer 5

lots of things lower serum thyroxine levels
no readily available biomarker for thyroid hormone activity - can use thyroglobulin autoantibodies
basal total T4 can be normal in dog with clinically overt hypothyroidism

Question 6

treatment

Answer 6

thyroxine tablets given orally
dose rate can be variably recommended
generally given once daily
twice daily dosing occasionally recommended
some individuals suggest using post-tablet monitoring