Thyroid Hormones and Their Effects
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Questions and Answers

What happens to the CNS in young animals during hyperthyroidism?

  • Increased growth and excitability (correct)
  • Slowed cerebration
  • Stunted cognitive development
  • Permanent damage to brain structure

    • Which symptom is commonly observed in cats with hyperthyroidism?

  • Alopecia
  • Hypertension (correct)
  • Weight gain
  • Bradycardia

    • What is the pathophysiological consequence of hypothyroidism on metabolism?

  • Accelerated metabolism
  • Increased protein synthesis
  • Decreased energy expenditure (correct)
  • Halted metabolism

    • What is the most likely cause of hyperthyroidism in cats?

    <p>Benign thyroid tumors secreting T4/T3</p> Signup and view all the answers

    What effect does excess T4/T3 have on muscle function?

    <p>Promotes quicker relaxation</p> Signup and view all the answers

    Which cardiovascular change is commonly observed in cats with hyperthyroidism?

    <p>Cardiac hypertrophy</p> Signup and view all the answers

    Which of the following is a consequence of hypertension in cats with hyperthyroidism?

    <p>Retinal detachment</p> Signup and view all the answers

    Which condition is characterized by stunted growth and heavy body weight in young animals?

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

    What cardiovascular effect is most prominently associated with hyperthyroidism?

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

    Which result from increased thyroid hormone levels can lead to symptoms of anxiety in affected individuals?

    <p>Increased metabolism</p> Signup and view all the answers

    What symptom would most likely indicate hypothyroidism in an adult animal?

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

    Which clinical sign is particularly indicative of advanced hyperthyroidism in cats?

    <p>Increased appetite combined with weight loss</p> Signup and view all the answers

    How does hyperthyroidism affect the metabolic processes in cats?

    <p>It enhances glycolysis and lipolysis, increasing ATP production</p> Signup and view all the answers

    Which of the following is a common cardiovascular change associated with feline hyperthyroidism?

    <p>Cardiac hypertrophy</p> Signup and view all the answers

    What potential electrolyte abnormality might be seen in cats suffering from hyperthyroidism?

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

    Which factor is believed to trigger the development of benign thyroid tumors leading to hyperthyroidism in cats?

    <p>Chemical exposure</p> Signup and view all the answers

    Which behavioral change is commonly observed in cats with hyperthyroidism?

    <p>Irritability and aggression</p> Signup and view all the answers

    What is a notable change in skin condition seen in hyperthyroid cats?

    <p>Rapid claw growth</p> Signup and view all the answers

    Which physiological mechanism is NOT influenced by excess T4/T3 in hyperthyroid cats?

    <p>Decrease in core body temperature</p> Signup and view all the answers

    In hyperthyroidism, what causes the increased metabolic rate across all organs?

    <p>Elevated levels of T4/T3 hormones</p> Signup and view all the answers

    What is one of the primary contributing symptoms of tachycardia in hyperthyroid cats?

    <p>Increased cardiac contractility</p> Signup and view all the answers

    Which statement accurately describes a consequence of hyperthyroidism in adult animals?

    <p>It results in weight loss and increased metabolism.</p> Signup and view all the answers

    What physiological change is linked to hypothyroidism in young animals?

    <p>Delayed CNS and body growth with possible cretinism.</p> Signup and view all the answers

    How does hyperthyroidism affect the skin of affected animals?

    <p>Causes follicle atrophy and bilateral alopecia.</p> Signup and view all the answers

    Which symptoms are associated with hyperthyroid cats?

    <p>Pacing, nervousness, and excessive grooming.</p> Signup and view all the answers

    What circulatory effect is typically seen in hyperthyroid animals?

    <p>Tachycardia and hypertension.</p> Signup and view all the answers

    How would a deficiency in thyroid hormones affect adult animals?

    <p>It results in lethargy and potential weight gain.</p> Signup and view all the answers

    Which of the following best describes the clinical signs of thyroid hormone excess?

    <p>Increased nervousness and insomnia.</p> Signup and view all the answers

    What effect do T3 and T4 hormones have on body temperature regulation?

    <p>They increase body temperature through enhanced metabolic rate.</p> Signup and view all the answers

    Which of the following clinical signs would least likely indicate hyperthyroidism in cats?

    <p>Weight gain</p> Signup and view all the answers

    What underlying factor is believed to stimulate the development of adenomas in the thyroid glands of cats?

    <p>Chemical exposure</p> Signup and view all the answers

    Which change in body function is associated with the impact of increased T4/T3 levels on muscle characteristics?

    <p>Increased protein synthesis</p> Signup and view all the answers

    Tachycardia in hyperthyroid cats is primarily due to which of the following factors?

    <p>Increased Beta 1 adrenoreceptors</p> Signup and view all the answers

    Which clinical sign is least associated with hyperthyroidism in cats despite being a common symptom in other conditions?

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

    In hyperthyroidism, changes to skin condition are often a result of what underlying issue?

    <p>Behavioral changes</p> Signup and view all the answers

    What effect does hyperthyroidism have on renal function in cats?

    <p>Electrolyte abnormalities</p> Signup and view all the answers

    Which physiological effect of excess thyroid hormones potentially contributes to symptoms of anxiety in hyperthyroid cats?

    <p>Increased sympathetic activity</p> Signup and view all the answers

    Which statement about the metabolic effects of hyperthyroidism is accurate?

    <p>It increases heat production.</p> Signup and view all the answers

    What is the likely clinical consequence of prolonged hypertension in cats with hyperthyroidism?

    <p>Renal dysfunction</p> Signup and view all the answers

    Study Notes

    Thyroid Hormone - Selected Effects on Body Tissues

    • Thyroid hormone impacts multiple bodily systems in both excess and deficient conditions.
    • Excess thyroid hormone (Hyperthyroidism) leads to accelerated growth and weight loss.
    • Deficient thyroid hormone (Hypothyroidism) leads to retarded growth and weight gain.
    • Hyperthyroidism stimulates all body functions, leading to nervousness, excitability, anxiety, insomnia, tachycardia, hypertension, and tachypnea.
    • Hypothyroidism slows down all body functions, leading to lethargy, somnolence, and follicle atrophy.
    • Hyperthyroidism effects on skin: follicle atrophy leads to bilateral alopecia, myxedema, and pigmentation.
    • Hypothyroidism effects on skin: follicle atrophy leads to bilateral alopecia, myxedema, and pigmentation.

    Hyperthyroidism / Thyrotoxicosis (in Cats)

    • Hyperthyroidism is excessive secretion of thyroid hormones.
    • Commonly occurs in middle-aged to old cats.
    • Rare in other species.
    • Mostly caused by benign thyroid tumors secreting T4/T3 (adenomas).
    • Cause of adenomas is unknown, but chemicals are believed to stimulate cell division in the thyroid gland.

    Hyperthyroidism: Old Cats

    • Hyperthyroidism is a common endocrine disorder in older cats.
    • Clinical presentation is slow and progressive.

    Hyperthyroidism / Thyrotoxicosis (in Cats)

    • Clinical Signs:
      • Weight loss, muscle weakness, and wasting, mild fatty liver syndrome.
      • Normal or increased appetite (polyphagia).
      • Hyperactivity, nervousness, and anxiety.
      • Heat intolerance and increased skin temperature.
      • Tachycardia and hypertension.
      • Polyuria and polydipsia (due to medullary washout and hypertension).
      • Vomiting and diarrhea.
      • Skin changes (matted hair or alopecia due to behavioral changes; rapid claw growth).

    Hyperthyroidism

    • Excess T4/T3 increases metabolic rate, leading to increased glycolysis, lipolysis, ATP production, and heat production.
    • Increased metabolism leads to protein catabolism, resulting in muscle weakness and weight loss.
    • Excess hormones promote quicker muscle relaxation and favors contraction, leading to hyperactivity.
    • Increased beta-1 adrenoreceptors increase sympathetic nervous system activity, leading to hyperactivity, increased core body temperature, and changes in behavior.
    • Increased protein synthesis of Myosin and Actin contributes to cardiac hypertrophy.
    • Increased metabolism leads to vomiting, alopecia, diarrhea, and vocalizations.
    • Increase in Ca pumps and Ca-gated channels leads to tachycardia and increased contractility.
    • Blood pressure increases, leading to retinopathy, renal dysfunction, electrolyte abnormalities, and polyuria/polydipsia.

    Hypothyroidism (in Dogs)

    • Insufficient production or secretion of thyroid hormone.

    Thyroid Hormone

    • Thyroid hormone (TH) has multiple effects on body tissues.
    • In young animals, excess TH accelerates growth but can result in early closure of epiphyses, leading to stunted and heavy bodies.
    • In adult animals, excess TH causes weight loss and increased metabolism.
    • In young animals, deficiency of TH retards CNS and body growth, resulting in cretinism.
    • In adult animals, deficiency of TH causes lethargy and weight gain.

    Hyperthyroidism

    • Hyperthyroidism is excessive secretion of thyroid hormones, commonly seen in middle-aged to older cats.
    • Benign thyroid tumors secreting T4/T3 (adenomas) are the primary cause.
    • Clinical signs include weight loss, muscle weakness, polyphagia, hyperactivity, heat intolerance, tachycardia, hypertension, polyuria/polydipsia, vomiting, diarrhea, and skin changes.
    • Excess T4/T3 increases metabolic rate, leading to increased glycolysis and lipolysis, ATP production, protein catabolism, and heat production.
    • Increased calcium pumps accelerate muscle relaxation, while increased calcium-gated channels enhance contraction, further contributing to muscle weakness and hyperactivity.
    • Increased beta-1 adrenoreceptors amplify sympathetic division activity, resulting in hyperactivity and elevated core body temperature.
    • Further effects include tachycardia, cardiac hypertrophy, hypertension, retinopathy, renal dysfunction, electrolyte abnormalities, and PU/PD.

    Hypothyroidism

    • Hypothyroidism is insufficient production or secretion of thyroid hormones, commonly seen in dogs.

    Thyroid Gland

    • Thyroxine (T4) and Triiodothyronine (T3) are produced by the thyroid gland

    Hyperthyroidism

    • Common in middle-aged and old cats
    • Caused by benign thyroid tumors called adenomas
    • Clinical Signs: Weight loss (despite increased appetite), muscle weakness, hyperactivity, heat intolerance, tachycardia, hypertension, polyuria, polydipsia, vomiting, diarrhea, alopecia, and rapid claw growth
    • Underlying Mechanisms:
      • Increased metabolic rate, leading to weight loss (due to increased glycolysis and lipolysis)
      • Increased protein catabolism, leading to muscle weakness
      • Increased calcium pump activity, leading to quicker muscle relaxation
      • Increased calcium-gated channel activity, leading to favored contraction in certain muscles
      • Increased beta-1 adrenoreceptor activity, leading to an increase in sympathetic nervous system activity and hyperactivity.
      • Increased Type V1 Myosin, influencing contractility
      • Influences protein synthesis, leading to an increase in myosin and actin

    Hypothyroidism

    • Common in dogs
    • Caused by insufficient production of thyroid hormones
    • Clinical Signs: Weight gain, lethargy, slow heart rate, decreased appetite, hair loss, cold intolerance, slow reflexes, and decreased mental activity.

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    Description

    This quiz explores the effects of thyroid hormones on body tissues, focusing on hyperthyroidism and hypothyroidism. Understand the physiological impacts of both excess and deficient thyroid hormone levels, including their influences on growth, metabolism, and specific body functions. Special attention is given to hyperthyroidism in cats and its distinct features.

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