Hypothyroidism Flashcards

Question

9 major functions of thyroid hormones

Answer 1

1. Anabolism (in physiological levels) or catabolism (in excess) 2. Increase weight (physiological) or decrease weight (in excess) 3. Increase heart rate 4. Increase blood pressure 5. Increase body temperature 6. Increase gut motility 7. Increase CNS activity 8. Are required for growth 9. Are required for reproduction

Answer 2

-Periparturient mortality (around and just before birth) -Low birth weights -Uterine inertia (total or partial absence of contractions) -Irregular estrus -Testicular atrophy -Low libido/subfertility

Answer 3

Swelling of skin - rounding of facial features Hyaluronic acid Myxedematous coma - rare, life-threatening clinical condition that represents severe hypothyroidism with physiologic decompensation --> hypothermia, depressed mental state, hypotension, bradycardia etc.

Answer 4

1. Clinical examination 2. Hematology 3. Biochemistry panel 4. Functional tests

Answer 5

Normocytic normochromic nonregenerative anemia

Answer 6

Hypercholesteremia (because this is rare in other conditions) Other findings: -Hypertriglyceridemia -Increased ALT, ALP -Increased creatine kinase

Answer 7

Most common form is iatrogenic hypothyroidism after treatment for hyperthyroidism. Naturally occuring hypothyroidism is possible, but extremely rare.

Answer 8

4-10 years old Mid- to large-size breeds Rare in toy and miniature breeds

Answer 9

Total T4 concentration is often used as a initial screening test but it can be problematic. A normal TT4 value can be used to rule out hypothyroidism. A low TT4-value is not diagnostic and you should do more tests. For example, TT4 might also be low in "Euthyroid sick" syndrome. (Except in cats TT4 is very good and the only test you need!)

Answer 10

A condition in which serum levels of thyroid hormones are low in patients who have nonthyroidal systemic illness but who are actually euthyroid. Diagnosis is based on excluding hypothyroidism. Some examples: starvation, trauma, myocardial infaction, chronic kidney disease, diabetic ketoacidosis, cirrhosis, sepsis, drugs...

Answer 11

-Glucocorticoids - decrease TT4 and T4 -NSAIDs - decrease TT4 -Barbiturates - decrease TT4 and T4, mildly incease cTSH -Clomipramine - Decrease TT4, T4, TT3 -Thyroid hormone replacement therapy - Decreases cTSH through negative feedback loop

Answer 12

Helps differentiate low T4 of hypothyroidism from other causes TSH should not be interpreted alone! Can be within reference intercal in a high proportion of hypothyroid dogs

Answer 13

Less affected by non-thyroidal illness and drug therapies than TT4. Decreased values are more specific for hypothyroidism than TT4. More expensive and complicated to measure than TT4.

Answer 14

1. Measure TT4 and TSH together in all cases. 2. If TT4 is low and TSH is high, diagnosis is nearly certain. 3. Take free T4 if one of these conditions is present: a) TT4 and TSH are inconclusive b) antithyroglobuline antibodies are suspected c) nonthyroidal illness exists 4. Be aware of the effects that nonthyroidal illness and medications have on thyroid function tests 5. Appropriate response to levothyroxine administration should confirm diagnosis + Clinical signs of hypothyroidism

Answer 15

They may interfere with the determination of thyroid hormone concentrations. --> usually false negative, sometimes, false positives They are useful for diagnosis of autimmune thyroiditis but are not measures of thyroid functions.

Answer 16

-TSH stimulation test -TRH stimulation test -Scintigraphy -Histopathology -Ultrasound

Answer 17

Evaluates the reserve function of the thyroid gland. Is considered to be more reliable than any other single individual test for canine hypothyroidism.

Answer 18

Idea is that TRH stimulates release of TSH which stimulates production of T4 and T3. Can be used to differentiate secondary and tertiary hypothyroidism, or between primary and nonthyroidal illness.

Answer 19

T3 is the metabolically active form of T4. Only 50% is secreted by thyroid gland, other 50% is formed by deiodination of T4 in peripheral tissues. In general, does not really accurately reflect thyroid function, not a useful test.

Answer 20

Lifelong treatment with levothyroxine.

Answer 21

Excellent in most cases. Individual variation. Check-up every 1/2 year. With myxedema coma, prognosis is worse. In case of congenital version, dog may have residual mental retardation and skeletal abnormalities.

Answer 22

1. Diagnosis can be very challenging in some dogs. 2. Hypothyroidism should be on the differencial list of many sick dogs. 3. Euthyroid sick syndrome is clinically very important. 4. Autoantibodies may interfere with the determination of thyroid hormone concentrations.