Hypothyroidism Flashcards
What is the most common pathogenesis of hypothyroidism?
Immune mediated destruction of the thyroid tissue (acquired)
can also be congenital due to enzyme deficiencies in the enzymes that make thyroid hormone
What are the clinical signs of hypothyroidism?
Lethargic and disinterested
Possibly overweight
Possibly exercise intolerant/joint pain
Dermal changes - alopecia, hyperpigmentation, thickening of the skin/dermal folds
Infertility in males and females
Occasionally neuro signs
TRAGIC FACIAL EXPRESSION :( (sometimes)
What is the prevelance of hypothyroidism in the UK dog population?
Around 1%
Not that big
Why do you get dermal changes sometimes?
Thyroid hormone interferes with hair cycle and you get alopecia
Sedcondary to this there is thickening and hyperpigmentation due to exposure to UV radiation
Why might they appear to have a denser hair coat?
Hair has fallen out but stuck in hair coat, if you groomed them it would all fall out
What is the coloquial term for congenital hypothyroidism?
Cretinism
Do you get increased thyroid size with hypothyroidism?
Yes can do, gland responds to stimulation due to lack of circulating hormone and becomes hypertrophied
What will you notice on a radiograph of a congenital hypothyroid puppy?
epiphysial dysgenesis. no calcification at epiphysis
What clinpath findings do you have with hypothyroid?
Most have mild non regenerative anaemia
Around 60% have elevated serum cholesterol
Around 40% have elevated serum creatinine kinase
Proteinuria sometimes
Very non specific
What diagnostic tools can you use in the acquired form of hypothyroidism?
basal total T4
basal free T4
baal TSH
TRH response test
TSH response test
Thyroglobulin autoantibodies
What other conditions can cause decreased levels of thyroid related hormones?
HAC or ANY other disease which increases circulating glucocorticoids, hence not a very specific test
Which hormone assay is probably the most reliable indicator of thyroid function?
Thyroid stimulating hormone. Should be high with a low T4
Not very sensitive or that specific but it is used
Is it possible to diagnose hypothyroidism from Tg autoantibodies?
No! They are a marker for immune mediated thyroid disease but no more than that.
Very low sensitivity and specificity
What is the most common test done to diagnose hypothyroidism and what’s its specificity?
Basal Total T4 with Basal TSH
95% specificity
How do you treat hypothyroidism?
Thyroxine tablets
Give 20 mg/kg SID
Should see a response within 3 weeks if not diagnosis probably wrong
