Canine Thyroid Hormone Autoantibodies Quiz
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Questions and Answers

What are the two most common causes of adult-onset primary hypothyroidism in dogs?

  • Autoimmune thyroiditis and excessive activity of the adaptive immune system
  • Lymphocytic thyroiditis and idiopathic atrophy of the thyroid gland (correct)
  • Destruction of the thyroid gland and secondary fibrosis
  • Low serum thyroid hormone concentrations and haircoat changes

    • What clinical features are used to diagnose hypothyroidism?

  • Weight loss and excessive thirst
  • Lethargy and obesity (correct)
  • High serum thyroid hormone concentrations and weight gain
  • Haircoat changes and excessive activity

    • What is the most common species to develop hypothyroidism?

  • Cats
  • Horses
  • Dogs (correct)
  • Domestic animals

    • What characterizes lymphocytic thyroiditis?

    <p>Diffuse infiltration of the gland by lymphocytes, plasma cells, and macrophages</p> Signup and view all the answers

    What is the recommended frequency for checking serum T4 (with or without T3) concentrations after the dosage is stabilized?

    <p>1-2 times per year</p> Signup and view all the answers

    What are the clinical signs of hypothyroidism in animals?

    <p>Lethargy, weight gain, and haircoat and skin changes</p> Signup and view all the answers

    What is the preferred treatment for hypothyroidism in animals?

    <p>Synthetic thyroid hormone replacement</p> Signup and view all the answers

    What is the most common cause of secondary hypothyroidism in dogs?

    <p>Destruction of pituitary thyrotrophs by a tumor</p> Signup and view all the answers

    Which breed of dogs have been reported to have congenital secondary hypothyroidism associated with clinical signs of disproportionate dwarfism, lethargy, gait abnormalities, and constipation?

    <p>Giant Schnauzers</p> Signup and view all the answers

    What is the most common form of hypothyroidism in cats?

    <p>Iatrogenic hypothyroidism</p> Signup and view all the answers

    What is the recognized cause of congenital hypothyroidism in cats where the thyroid gland is unable to respond to TSH?

    <p>An inability of the thyroid gland to respond to TSH</p> Signup and view all the answers

    What may develop in association with a specific syndrome of neonatal foals characterized by thyroid gland hyperplasia and multiple congenital musculoskeletal anomalies?

    <p>Thyroid hyperplasia and musculoskeletal deformities syndrome</p> Signup and view all the answers

    Which animals have hypothyroidism that is commonly misdiagnosed and may be related to feeding a high nitrate diet to pregnant mares?

    <p>Foals</p> Signup and view all the answers

    What is the age range in which hypothyroidism is most common in dogs?

    <p>4–10 years old</p> Signup and view all the answers

    In which size range of dogs is hypothyroidism rare?

    <p><em>Toy</em> and <em>miniature</em> breeds</p> Signup and view all the answers

    What is the main limitation of the TSH stimulation test for thyroid function in dogs?

    <p>High expense of the test</p> Signup and view all the answers

    What is the recommended dose of human recombinant TSH for the TSH stimulation test in dogs?

    <p>75 mcg, IV</p> Signup and view all the answers

    What is the purpose of using ultrasonography and scintigraphy in the diagnosis of hypothyroidism in dogs?

    <p>To differentiate between hypothyroidism and euthyroid sick syndrome</p> Signup and view all the answers

    What is the most practical approach to confirming the diagnosis of hypothyroidism in some cases?

    <p>Therapeutic trial using appropriate guidelines</p> Signup and view all the answers

    Why should every attempt be made to exclude nonthyroidal illness before starting a therapeutic trial for hypothyroidism?

    <p>To ensure accurate diagnosis and appropriate treatment</p> Signup and view all the answers

    What is the recommended dosage of thyroxine supplementation for dogs with hypothyroidism?

    <p>20 mcg/kg, once to twice daily</p> Signup and view all the answers

    What should be done if response to thyroxine supplementation is positive in dogs with hypothyroidism?

    <p>Withdraw therapy to confirm that clinical signs return</p> Signup and view all the answers

    How can hypothyroidism be diagnosed in cats based on the text?

    <p>Detecting low serum concentrations of total T4 and T3</p> Signup and view all the answers

    What can be detected in as many as half of dogs with hypothyroidism and is believed to reflect a state of autoimmune thyroiditis?

    <p>Circulating antithyroglobulin antibodies</p> Signup and view all the answers

    Why can measurement of antithyroglobulin antibody titers not be used alone to confirm a diagnosis of hypothyroidism?

    <p>A positive titer may occur in euthyroid dogs with early stages of lymphocytic thyroiditis</p> Signup and view all the answers

    What are the earliest dermatologic changes in dogs with hypothyroidism?

    <p>Dryness, excessive shedding, and retarded regrowth of hair</p> Signup and view all the answers

    What is the classic behavior of a hypothyroid dog in terms of seeking heat?

    <p>Actively seeking heat</p> Signup and view all the answers

    What is the purpose of identifying dogs with autoimmune thyroid disease based on circulating antithyroglobulin antibodies?

    <p>To confirm a diagnosis of hypothyroidism</p> Signup and view all the answers

    What is the role of serum thyroglobulin autoantibody determinations in diagnosing hypothyroidism?

    <p>Identifying dogs with autoimmune thyroid disease</p> Signup and view all the answers

    In about two-thirds of dogs with hypothyroidism, what kind of alopecia is usually observed?

    <p>Bilaterally symmetric</p> Signup and view all the answers

    In dogs with moderate to severe hypothyroidism, what occurs in the skin as a secondary effect?

    <p>Thickening due to accumulation of glycosaminoglycans</p> Signup and view all the answers

    What is the extreme expression of severe hypothyroidism called?

    <p>Myxedema coma</p> Signup and view all the answers

    What are the prominent signs of congenital and juvenile-onset hypothyroidism?

    <p>Proportionate dwarfism and impaired mental development</p> Signup and view all the answers

    What leads to disproportionate dwarfism in primary congenital hypothyroidism?

    <p>Underdeveloped epiphyses throughout the long bones</p> Signup and view all the answers

    What are the primarily related clinical signs in dogs with congenital hypopituitarism (pituitary dwarfism)?

    <p>Proportionate dwarfism and loss of primary guard hairs</p> Signup and view all the answers

    What clinical signs are associated with advanced or severe hypothyroidism in adult cats?

    <p>Bradycardia and bilaterally symmetric alopecia</p> Signup and view all the answers

    What are the typical clinical signs seen in young cats with congenital or juvenile-onset hypothyroidism?

    <p>Mental dullness and bradycardia</p> Signup and view all the answers

    How is the diagnosis of hypothyroidism confirmed?

    <p>Based on suggestive clinical findings confirmed by serum thyroid hormone testing</p> Signup and view all the answers

    What is the classic hematologic finding associated with hypothyroidism?

    <p>Normocytic, normochromic, nonregenerative anemia</p> Signup and view all the answers

    What is the most commonly performed static thyroid hormone measurement?

    <p>Total T4 measurement</p> Signup and view all the answers

    Which test has better accuracy than the analogue methods for differentiating euthyroid dogs from hypothyroid dogs?

    <p>Measurement of free T4 by equilibrium dialysis</p> Signup and view all the answers

    What is the classic serum biochemical abnormality associated with hypothyroidism?

    <p>Hypercholesterolemia</p> Signup and view all the answers

    What is the value of serum cholesterol determination as a screening test for hypothyroidism?

    <p>It is a sensitive and inexpensive biochemical marker</p> Signup and view all the answers

    How can nonthyroidal illness affect basal T4 concentration in animals?

    <p>It usually decreases basal T4 concentration</p> Signup and view all the answers

    What is the most common type of hypothyroidism in dogs?

    <p>Primary hypothyroidism</p> Signup and view all the answers

    What percentage of dogs with confirmed hypothyroidism have their serum TSH concentrations remain within the reference range?

    <p>~20% - 40%</p> Signup and view all the answers

    What is the classic finding in serum biochemical abnormalities in dogs with hypothyroidism?

    <p>High serum concentrations of triglycerides and alkaline phosphatase</p> Signup and view all the answers

    What do high endogenous TSH concentrations indicate in animals with primary hypothyroidism?

    <p>Low serum T4 and/or free T4 concentrations</p> Signup and view all the answers

    Which test can be a useful adjunctive test for hypothyroidism in dogs, cats, and horses?

    <p>Serum TSH measurement</p> Signup and view all the answers

    What can lead to low serum thyroid hormone measurements in euthyroid animals?

    <p>Nonthyroidal factors such as nonthyroidal illness and certain drugs</p> Signup and view all the answers

    What is the recommended standard treatment for hypothyroidism in dogs and cats?

    <p>Oral administration of synthetic thyroid hormone levothyroxine (L-T4)</p> Signup and view all the answers

    What is the effect of glucocorticoids on thyroid function tests in dogs?

    <p>Decrease total T4 and sometimes free T4 concentrations</p> Signup and view all the answers

    Which breed may have serum total T4 and free T4 concentrations considerably lower than those of most other breeds?

    <p>Greyhounds</p> Signup and view all the answers

    What is the term used to describe an illness not involving the thyroid gland but can alter thyroid function tests?

    <p>Euthyroid sick syndrome</p> Signup and view all the answers

    Which medication can induce overt primary hypothyroidism with clinical signs in dogs?

    <p>Sulfonamides</p> Signup and view all the answers

    What happens to serum free T4 concentration in dogs with substantial nonthyroidal illness?

    <p>Decreases</p> Signup and view all the answers

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