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76 Cards in this Set
- Front
- Back
6 thyroid functions
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1. Maintains metabolic homeostasis
2. Normal development 3. Regulates myocardial gene expression 4. Stimulates metabolism of cholesterol to bile acids 5. Stimulates synthesis of proteins 6. Stimulates increased cellular demand for oxygen |
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Hypothyroidism Signs
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* Lethargy
* Weight gain * Alopecia * Cold intolerance * Bradycardia * Hypercholesterolemia |
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Hyperthyroidism Signs
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* Weight loss
* Polyphagia * Hyperactivity * Tachycardia * Vomiting |
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What is the enzyme responsible for catalyzing iodine/globulin into T4 & T3
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Thyroid peroxidase
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What is the enzyme responsible for catalyzing T4 to T3 in cells?
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5’ Deiodinase
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What drug types cause inhibition of 5'-deiodinase?
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* Glucocorticoids
* Quinidine |
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What drug types cause displacement of thyroid function?
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* Salicylates
* Furosemide * Oleic acid * NSAIDs |
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What drug types intefere with thyroid hormone secretion?
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* Glucocorticoids
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What drug types cause increased clearance of thyroid function?
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* Phenobarbital
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What drugs involve iodine and affect thyroid function?
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* Potassium bromide
* Radiocontrast agents * TMPS |
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How do glucocorticoids in dogs effect thyroid function?
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* Lowers serum T3 (antiinflammtory dosage)
* T4 affected with chronic, high dose, daily therapy or immunosuppressive therapy. * May be due to inhibition of 5’-deiodinase, reduced availability of plasma T4, or interference w/ thyroid hormone secretion |
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How do glucocorticoids in cats and horses effect thyroid function?
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Has little effect on T4 in cat/horse
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How does use of anticonvulsants effect thyroid function?
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Decrease serum T4 concentrations
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How does use of Quinidine effect thyroid function?
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inhibit 5’-deiodinase
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How does use of Salicylates, furosemide, or oleic acid effect thyroid function?
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directly displace thyroid hormone from plasma binding sites
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How does use of NSAIDs effect thyroid function?
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because thyroid hormones are highly protein bound and NSAIDS can displace them
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How does use of Phenylbutazone (NSAID) effect thyroid function?
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Direct antithyroid (goitrogenic) effect, decreases total/free T4 in the horse
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How does use of Carprofen (NSAID) effect thyroid function?
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can cause a transient decrease in T4
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How does use of Radiocontrast agents effect thyroid function?
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Directly binds 5’-deiodinase or releases iodine to exert an antithyroid effect on the thyroid gland
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How does use of Trimethoprim/ Sulfamethoxazole effect thyroid function?
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T4 falls with long-term treatment due to interference with iodine metabolism
Thyroid Hormone Synthesis |
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What are the 2 thyroid hormone drugs?
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1. L-thyroxine (T4)
2. L-triiodothyronine (T3) |
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Why would an animal be given L-thyroxine (T4) instead of L-triiodothyronine (T3)?
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*Given to hypothyroid animals
* More physiological (in the body, T4 is released by the thyroid and then converted to T3) * Gives better serum balance of T3/T4 * less expensive * More consistent in bioavalability |
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Why would an animal be given L-triiodothyronine (T3) instead of L-thyroxine (T4)?
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* Given to hypothyroid animals
* Non-responsive to T4 * Less desirable b/c less physiologic |
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Three Anti-Thyroid drugs discussed in class
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1.Methimazole (MMI)
2.Propylthiouracil (PTU) 3.Radioactive Iodine |
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MOA of Methimazole (MMI)
and Propylthiouracil (PTU) (anti-thyroid drugs) |
* Blocks incorporation of iodine into thyroglobulin
* Prevents coupling of iodotyrosil groups * Inhibits thyroid peroxidase |
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Adverse Effects of Methimazole (MMI)
and Propylthiouracil (PTU) |
vomiting, GI signs, excoriations, liver toxicity
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Why is Propylthiouracil (PTU)
not used as much anymore? |
not used much anymore b/c autoimmune prob in cats; also inhibits 5’ diodinase
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MOA of Radioactive Iodine
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* Selectively destroys thyroid tissue after take up by thyroid gland
* Emits gamma rays and beta particles; most local tissue destroyed by beta particles |
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How is radioactive iodine given?
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orally
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Three Anti-Thyroid drugs discussed in class
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1.Methimazole (MMI)
2.Propylthiouracil (PTU) 3.Radioactive Iodine |
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MOA of Methimazole (MMI)
and Propylthiouracil (PTU) (anti-thyroid drugs) |
* Blocks incorporation of iodine into thyroglobulin
* Prevents coupling of iodotyrosil groups * Inhibits thyroid peroxidase |
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Adverse Effects of Methimazole (MMI)
and Propylthiouracil (PTU) |
vomiting, GI signs, excoriations, liver toxicity
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Why is Propylthiouracil (PTU)
not used as much anymore? |
not used much anymore b/c autoimmune prob in cats; also inhibits 5’ diodinase
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MOA of Radioactive Iodine
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* Selectively destroys thyroid tissue after take up by thyroid gland
* Emits gamma rays and beta particles; most local tissue destroyed by beta particles |
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How is radioactive iodine given?
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orally
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Hypoadrenocorticism Signs
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* Nausea
* Vomiting * Hyponatremia * Hyperkalemia * Lethargy * Dehydration |
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Hyperadrenocorticism Signs
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PU/PD
Polyphagia Lethargy Pot belly Thin skin Alopecia Muscle wasting |
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3 zones of the adrenal cortex? What is each zone responisble for?
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1. Zona Glomerulosa-Mineralocorticoids
2. Zona Fasiculata-Glucocorticoids 3. Zona Reticularis-Sex Hormones |
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Treatment of adrenal insufficiency involves physiologic replacement of glucocorticoids and mineralocorticoids
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Treatment of adrenal insufficiency involves physiologic replacement of glucocorticoids and mineralocorticoids
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What are the 2 mineralocorticoid drugs used to for treatment of adrenal insufficiency?
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1. Desoxycorticosterone
pivalate (DOCP) 2. Fludrocortisone acetate |
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MOA of Desoxycorticosterone
pivalate (DOCP) |
Acts like aldosterone to retain Na+ and secrete K+
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How often is Desoxycorticosterone
pivalate (DOCP) given? |
Given every 25 days
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In what species Desoxycorticosterone
pivalate (DOCP) is approved for? |
Approved for use in dogs
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MOA of Fludrocortisone acetate
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Acts like aldosterone to retain Na+ and secrete K+
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How often is Fludrocortisone acetate given?
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Given every day
* Can see GCC side effects |
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What 3 drugs are used to treat Pituitary and Adrenal dependant hyperadrenocorticism?
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1.Mitotane
2.Trilostane 3. Ketoconazole |
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MOA of Mitotane
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Selectively destroys zona fasciculata/reticularis
(less effect on glomerulosa – aldosterone) |
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Adverse effects of Mitotane
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GI signs, hypoglycemia, CNS depression, liver damage,electrolyte imbalances
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In what animals should Mitotane not be used in?
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Do not use in pregnant animals
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MOA of Trilostane
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Inhibits 3-Beta, hydroxysteroid dehydrogenase which
blocks synthesis of adrenal steroids (pregnenolone to progesterone doesn’t happen) |
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In what species is Trilostane FDA approved?
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FDA Approved in dogs
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What contraindications are associated with Trilostane?
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Pregnant animals - affects sex hormones
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Adverse effects of Trilostane
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vomiting, diarrhea, lethargy
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MOA of Ketoconazole
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Prevents conversion of lanosterol to cholesterol by
inhibiting CYP450 enzymes |
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Under what conditions is Ketoconazole used
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Used in animals that don’t respond well to trilostane/mitotane
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Why is Ketoconazole given in combination with other drugs?
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Used in combination with other drugs to decrease dose because
inhibits CYP450 enzymes, preventing metabolism of drug in liver |
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Adverse effects of Ketoconazole
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vomiting, diarrhea
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What 2 drugs are used for only Pituitary dependant hyperadrenocorticism?
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1.Selegiline (L-deprenyl)
2. Pergolide |
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MOA of Selegiline (L-deprenyl)
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Monoamine oxidase B inhibitor
B – dopamine breakdown is inhibited so increases dopamine |
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What does Selegiline (L-deprenyl) do to dopamine, ACTH, and cortisol?
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-Increases dopamine, decreases ACTH, decreases cortisol
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How does Selegiline (L-deprenyl) affect the disease process?
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Alters clinical signs, not disease process
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Adverse effects of Selegiline (L-deprenyl)
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generally safe, vomiting/diarrhea
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MOA of Pergolide
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Dopamine agonist @ D1 & D2 receptors
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Why is Pergolide no longer formulated
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-No longer formulated because of human cardiovascular effects
so must be compounded |
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What species is Pergolide used in?
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Used in horses
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Adverse effects of Pergolide
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Dopamine suppresses prolactin which inhibits lactation in
pregnant or nursing |
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How/where is insulin produced?
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Produced in Beta cells of islets of langerhans as preproinsulin then becomes proinsulin and finally becomes insulin
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Diabetes Mellitus Symptoms
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PU/PD
Polyphagia Weight loss Lethargy Hyperglycemia Glycosuria |
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Goal of treatment when using insulin
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want to get blood glucose close to normal, but avoid hypoglycemia
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MOA of all insulin replacers
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binds to insulin receptor and autophosphorylation occurs, other proteins are phosphorylated/dephosphorylated
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What are the actions of insulin drugs?
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* Facilitate cellular uptake & metabolism of glucose
* Promote glycogen/protein/fat synthesis * Uptake of ions into cells |
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What are the 3 fast acting insulin drugs? When do you use them?
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1. Regular human insulin
2. Lispro – synthetic human recombinant 3. Aspart – synthetic human recombinant * Use for complicated diabetes (not eating, emergency, diabetic ketoacidosis); act quickly but don’t last long |
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What are the 4 intermediate to long acting insulin drugs?
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1. NPH (isophane) – human insulin recombinant
2. Protamine zinc (pork insulin) t 3. Glargine – synthetic, used in cats 4. Detemir – synthetic, used in cats |
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What is the one insulin drug that is a sulfonylurea?
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Glipizide
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MOA of Glipizide
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inhibit ATP dep K+ channels, resulting in depolarization of beta cells and release of insulin
*** Glipizide is an oral hypoglycemic agent so must be capable of secreting insulin from beta cells |
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Adverse effect of Glipizide
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amyloid deposition in cats
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