Equine Thyrotoxicosis Quiz
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Questions and Answers

What is a common sign of thyrotoxicosis in horses?

  • Increased appetite
  • Nervousness (correct)
  • Weight gain
  • Decreased urination

    • What is the role of antithyroid thioureylene drugs?

  • Inhibit absorption of iodine
  • Inhibit the synthesis of thyroid hormones (correct)
  • Enhance the coupling of iodotyrosyl groups
  • Stimulate thyroid hormone production

    • What is a necessary action to confirm a diagnosis of thyrotoxicosis?

  • Monitor heart rate
  • Perform a urine test
  • Check for fever
  • Measure serum T4 and T3 concentrations (correct)

    • How do plants from the genus Brassica relate to thyroid hormone synthesis?

    <p>They exhibit antithyroid activity.</p> Signup and view all the answers

    What serum levels are typically monitored in horses undergoing levothyroxine therapy?

    <p>Serum T4 and TSH concentrations</p> Signup and view all the answers

    What is the initial form of insulin before it is cleaved to proinsulin?

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

    Which of the following accurately describes the relationship between dog insulin and porcine insulin?

    <p>Dog insulin is identical to porcine insulin.</p> Signup and view all the answers

    What triggers the secretion of insulin from beta cells?

    <p>Increased levels of Ca2+</p> Signup and view all the answers

    Which statement correctly describes the mechanism of insulin action?

    <p>Insulin initiates an intracellular signaling cascade.</p> Signup and view all the answers

    What is the primary function of beta cells in the pancreas?

    <p>To produce insulin</p> Signup and view all the answers

    What happens during exocytosis of insulin from beta cells?

    <p>Insulin is released into the bloodstream.</p> Signup and view all the answers

    Which of the following statements about diabetes is true?

    <p>Diabetes is associated with abnormal insulin secretion.</p> Signup and view all the answers

    Which process initiates the secretion of insulin from beta cells?

    <p>Closure of ATP-dependent potassium channels</p> Signup and view all the answers

    Which antithyroid drug is recognized as the drug of choice for hyperthyroidism in cats?

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

    What serious adverse effects are associated with Propylthiouracil (PTU)?

    <p>Autoimmune effects and hemolytic anemia</p> Signup and view all the answers

    How is Carbimazole metabolized to exert its antithyroid activity?

    <p>It is rapidly converted to methimazole</p> Signup and view all the answers

    What is a common adverse effect of Methimazole treatment?

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

    What is a dosing strategy recommended for Methimazole in managing feline hyperthyroidism?

    <p>Start with BID or TID, consider SID later</p> Signup and view all the answers

    What distinguishes Carbimazole from Methimazole in terms of side effects?

    <p>Fewer gastrointestinal side effects</p> Signup and view all the answers

    Which symptoms are considered signs of Methimazole toxicity that need periodic checking?

    <p>Anorexia and vomiting</p> Signup and view all the answers

    Which of the following statements about Methimazole is correct?

    <p>It can be given in oral or transdermal forms</p> Signup and view all the answers

    What is the primary cause of hyperadrenocorticism in dogs and horses?

    <p>Excess production of ACTH</p> Signup and view all the answers

    Which drug leads to the relative destruction of the zona fasciculata and reticularis in the adrenal gland?

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

    What is the typical dosing regimen of Mitotane for hyperadrenocorticism in dogs?

    <p>30–50 mg/kg once daily for 3–10 days</p> Signup and view all the answers

    Which of the following is a common side effect of Mitotane?

    <p>Mild liver damage</p> Signup and view all the answers

    Which drug is used to suppress the adrenal cortex by inhibiting the enzymatic conversion of steroids?

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

    What condition is Trilostane approved to treat aside from hyperadrenocorticism?

    <p>Adrenal carcinomas</p> Signup and view all the answers

    In cats, how variable is the efficacy of Mitotane compared to that in dogs?

    <p>Efficacy is variable</p> Signup and view all the answers

    What is a potential side effect of Trilostane treatment?

    <p>Increased size of adrenal glands</p> Signup and view all the answers

    Why can't insulin be administered orally?

    <p>It is broken down in the intestine.</p> Signup and view all the answers

    What is the typical measurement unit for insulin in veterinary medicine?

    <p>International units (IU)</p> Signup and view all the answers

    What is the primary action of glucagon-like peptide 1 (GLP-1)?

    <p>Stimulates insulin secretion after food intake.</p> Signup and view all the answers

    Which insulin is recommended for use during diabetic ketoacidosis?

    <p>Lispro insulin</p> Signup and view all the answers

    Which side effects are associated with the use of sulfonylureas like glipizide?

    <p>Hypoglycemia and gastrointestinal upset.</p> Signup and view all the answers

    What is the mechanism of action for the oral hypoglycemic agent acarbose?

    <p>Delays carbohydrate absorption.</p> Signup and view all the answers

    What is a common treatment for mineralocorticoid deficiency in animals?

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

    What adverse effects can occur with insulin therapy?

    <p>Hypoglycemia and convulsions.</p> Signup and view all the answers

    Which insulin type has a prolonged duration and is used for uncomplicated diabetes?

    <p>NPH insulin</p> Signup and view all the answers

    What is the preferred site for insulin injections in dogs?

    <p>Flank or side of the chest</p> Signup and view all the answers

    What action does metformin primarily perform?

    <p>Reduces hepatic glucose output.</p> Signup and view all the answers

    Which agent can manage hyperinsulin-associated hypoglycemia?

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

    What is the ideal starting insulin dose for diabetic dogs and cats?

    <p>0.5 to 1.0 U/kg</p> Signup and view all the answers

    What is the role of thyroid peroxidase (TPO) in the synthesis of thyroid hormones?

    <p>It converts iodide to iodine and incorporates it into thyroglobulin.</p> Signup and view all the answers

    Which thyroid hormone is primarily secreted by the thyroid gland?

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

    How do high levels of T3 and T4 affect TRH and TSH secretion?

    <p>They inhibit TRH and TSH secretion.</p> Signup and view all the answers

    What is the primary mechanism through which thyroid hormones are released from the thyroid gland?

    <p>Endocytosis of iodinated thyroglobulin</p> Signup and view all the answers

    What is the function of 5’-deiodinase in thyroid hormone metabolism?

    <p>It converts T4 into T3.</p> Signup and view all the answers

    Which condition can decrease serum T3 concentrations?

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

    What is a common consequence of taking synthetic T3 as a treatment?

    <p>Potential development of iatrogenic hyperthyroidism</p> Signup and view all the answers

    What is the main advantage of using synthetic L-thyroxine (T4) for hormone replacement therapy?

    <p>It has a defined and stable hormone concentration.</p> Signup and view all the answers

    Which thyroid hormone preparation is indicated if an animal does not respond to synthetic T4?

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

    Which process represents how thyroid hormones are transported in the bloodstream?

    <p>Binding with thyroid binding protein (TBP)</p> Signup and view all the answers

    What is the effect of thyroid hormones on metabolic rate?

    <p>They increase metabolic activity and thermogenesis.</p> Signup and view all the answers

    What is the primary purpose of thyroid hormone receptor (THR) binding in the cells?

    <p>To form a transcription factor complex that regulates gene expression</p> Signup and view all the answers

    Which of the following is NOT a thyroid hormone preparation?

    <p>Diethylene glycol</p> Signup and view all the answers

    Which of the following represents a long-term effect of thyroid hormones on the body?

    <p>Enhanced protein synthesis and growth.</p> Signup and view all the answers

    Study Notes

    Endocrine Pharmacology II

    • Course instructor: Nuno Coelho
    • Course: Pharmacology and therapeutics II
    • Level: 3rd year Veterinary Medicine

    Thyroid Hormone and Antithyroid Drugs

    • Thyroid diseases are common in veterinary medicine
    • Hyperthyroidism in cats
    • Hypothyroidism in dogs
    • T3 (triiodothyronine) and T4 (thyroxine) are the main thyroid hormones produced by the thyroid gland

    Endocrine System Introduction

    • Pituitary gland plays a crucial role in stimulating the secretion of glucocorticoids, mineralocorticoids, and adrenal androgens.
    • Synthetic preparations of ACTH are used in diagnosis of primary adrenal hypofunction (hypoadrenocorticism)
    • Thyroid gland, reproductive endocrinology, pancreas are part of the endocrine system

    Thyroid Hormone Synthesis

    • Thyroglobulin is synthesized and stored as colloid.
    • Iodide enters follicular cells via Na+/I- symporter (NIS)
    • Iodide is oxidized to iodine (I2) by thyroid peroxidase (TPO)
    • Iodine is incorporated into tyrosine residues of thyroglobulin by TPO
    • MIT (monoiodotyrosine) and DIT (diiodotyrosine) are formed.
    • DIT + DIT becomes T4; MIT + DIT becomes T3
    • T3 and T4 are released into the bloodstream.

    Regulation of Thyroid Hormone Synthesis

    • Thyroid-releasing hormone (TRH) from hypothalamus (when T3 and T4 blood levels are low)
    • Thyroid-stimulating hormone (TSH) from pituitary after stimulated by TRH
    • Regulation is by negative feedback
    • High levels of T3 and T4 inhibit TRH and TSH

    Thyroid Hormone Secretion and Transport

    • Thyroid hormones are stored in colloid.
    • TSH stimulates endocytosis of thyroglobulin.
    • Within lysosomes, thyroglobulin is hydrolysed.
    • T3 and T4 are released and travel in blood bound to thyroxine-binding protein (TBP).
    • T4 is the main secretory product but is less potent and converted to T3 in target tissues.

    Factors Affecting Thyroid Metabolism

    • Illness and malnutrition (chronic starvation, malnutrition, diabetes mellitus, liver and kidney disease) decrease serum T3 concentrations.
    • The body employs adaptive mechanisms to maintain protein levels and blunt metabolism during illness
    • Drugs can affect thyroid hormone metabolism by affecting thyroid hormone production, transport, or metabolism). Examples include glucocorticoids, phenobarbital, trimethoprim/sulfonamides, and non-steroidal anti-inflammatory drugs.

    Effects of Thyroid Hormones

    • Calorigenesis and thermoregulation
    • Growth and maturation
    • Dermatological effects on lipids and carbohydrates
    • Cardiovascular function
    • Neuromuscular function
    • Reproductive function
    • Gastrointestinal function
    • Immunological function
    • Hematological function

    Drugs Associated with Thyroid Hormones

    • Thyroid hormone preparations (crude hormones from thyroid gland, synthetic L-thyroxine (T4), synthetic L-triiodothyronine (T3), combinations)
    • Antithyroid drugs (inhibitors of thyroid peroxidase (TPO), example: methimazole/thiamazole)

    Thyroid Hormone Preparations (Detailed)

    • Crude hormones prepared from thyroid gland
    • Synthetic L-thyroxine (T4) is the hormone of choice for hormone replacement in all species.
    • Synthetic L-triiodothyronine (T3) is used if animals don't respond to T4
    • Combinations of T3 and T4

    Antithyroid Drugs (Detailed)

    • Methimazole (Tapazole) is the drug of choice for cats
    • Carbimazole is derived from methimazole
    • Propylthiouracil (PTU) also inhibits deiodinase 1, with side effects including autoimmune and hemolytic anemia
    • Potassium iodine (Lugol's) inhibits organification and coupling steps of thyroid hormone synthesis.

    Oral Hypoglycemic Agents

    • Sulfonylureas (glipizide) stimulate the pancreas, inhibit ATP-dependent K channels, causing depolarization and release of insulin
    • Metformin reduces hepatic glucose output and improves peripheral insulin sensitivity
    • Acarbose delays and reduces postprandial hyperglycemia by inhibiting alpha-glucosidase
    • Glucagon-like peptide-1 (GLP-1) agonists (Ozempic) augment insulin secretion after intake
    • SGLT2 inhibitors (Velagliflozin as in Senvelgo) inhibit glucose reabsorption from kidney, thus increasing glucose elimination in the urine

    Hyperglicemic Agents

    • Diazoxide inhibits insulin secretion
    • Octreotide (somatostatin analogue) is used to manage hyperinsulin-associatied hypoglycemia in dogs

    Insulin Preparations and Considerations

    • Insulin preparations (fast-acting (lispro, aspart, regular), intermediate-acting (NPH, lente), long-acting (glargine, detemir))
    • The choice and frequency depend on the specific condition and effects
    • Administration (typically by injection, IM, SC, or IV), using specialized syringes
    • Administration can sometimes be daily or twice daily.
    • Monitoring of blood glucose levels is essential
    • Insulin resistance, clinical indications, and therapy

    Adrenal Gland Function and Drugs

    • Adrenocorticotropin (ACTH) is crucial for stimulating the secretion of glucocorticoids (including cortisol), mineralocorticoids, and adrenal androgens from the adrenal cortex.
    • Synthetic ACTH preparations are used in diagnosis of primary adrenal hypofunction
    • Treatment of mineralocorticoid deficiency includes Deoxycorticosterone Pivalate (DOCP), mimicking aldosterone effect or Fludrocortisone for use for mineralocorticoid and glucocorticoid activity
    • Treatment of hyperadrenocorticism (Cushing's disease) involves drugs that reduce cortisol production (mitotane and trilostane)

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    Description

    Test your knowledge about thyrotoxicosis in horses and its diagnosis. This quiz covers key concepts such as the role of antithyroid thioureylene drugs and the relationship between certain plants and thyroid hormone synthesis. It's essential for anyone interested in veterinary medicine and equine health.

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