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41 Cards in this Set
- Front
- Back
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What drug is a synthetic T3 analog?
What drug is a synthetic T4 analog? What is each indicated for? |
T3 = Liothyronine - Myxoedema Coma, Thyroid Cancer
T4 = Thyroxine - Hypothyroidism |
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What is the normal TSH range when assessing Hypo vs Hyperthyroidism?
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Normal TSH = 0.5 - 5.0 mU/L
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What medications decrease T4 absorption?
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Sodium Polystyrene Sulfonate
Cholestyramine Iron Calcium supplements Aluminum Hydroxide Sucralfate |
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What medications increase Hepatic P450 enzymes and hepatic T4 excretion?
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Rifampin
Phenytoin Carbamazepine |
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What disease states decrease T4 absorption?
What conditions can increase Thyroglobulin-binding protein and reduce T4 bioavailability? |
Small Intestinal Disease (Celiac disease, Crohn's, short bowel)
Pregnancy, Estrogens, Hepatitis |
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When treating hypothyroidism, what type of drug do you want to avoid?
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Sedatives
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After total thyroidectomy, a woman is placed on levothyroxine. Which attribute is true about this drug?
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It is partly converted to T3 in the body
Wrong answers corrected: It is administered once daily T3 is the most potent, not T4 T4 has a half life of about a week Iron supplements decrease its bioavailability. |
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Describe the treatment options by drug class (and what that class does) in treating hyperthyroidism
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In hyperthyroidism, the objective is to inhibit thyroid hormone synthesis.
(1) Inhibit Iodide Uptake (2) Inhibit Organification and Hormone Release - Iodides, Thioamines (3) Inhibitors of Peripheral Thyroid Metabolism - Beta Blockers, Ipodate |
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Name the 3 inhibitors of iodide uptake.
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Perchlorate
Thiocyanate Pertechnetate |
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What is the mechanism of action for these drugs?
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They have a molecular radius similar to the Iodide anion.
They compete with Iodide for the NIS decreasing uptake of iodide. |
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When treating hypothyroidism, what type of drug do you want to avoid?
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Sedatives
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After total thyroidectomy, a woman is placed on levothyroxine. Which attribute is true about this drug?
|
It is partly converted to T3 in the body
Wrong answers corrected: It is administered once daily T3 is the most potent, not T4 T4 has a half life of about a week Iron supplements decrease its bioavailability. |
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Describe the treatment options by drug class (and what that class does) in treating hyperthyroidism
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In hyperthyroidism, the objective is to inhibit thyroid hormone synthesis.
(1) Inhibit Iodide Uptake (2) Inhibit Organification and Hormone Release - Iodides, Thioamines (3) Inhibitors of Peripheral Thyroid Metabolism - Beta Blockers, Ipodate |
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Name the 3 inhibitors of iodide uptake.
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Perchlorate
Thiocyanate Pertechnetate |
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What is the mechanism of action for these drugs?
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They have a molecular radius similar to the Iodide anion.
They compete with Iodide for the NIS decreasing uptake of iodide. |
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What is a common adverse effect of these compounds?
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They are used in radiocontrast studies and can cause hypothyroidism.
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Inhibitors of organification and hormone release: Iodides and Thioamines. How do iodides work?
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They work via the Wolff-Chaikoff effect, whereby they decrease NIS expression. This reduces the transcription of thyroid peroxidase and reduces iodination of TG by reducing Hydrogen Peroxide generation.
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What is the drawback?
What is the major indication for this drug class? |
The effects are transient.
It is primarily used short-term before surgical resection to reduce the vascularity of the gland. |
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How was this drug class used during the Chernobyl accident?
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People were given inorganic iodide to prevent the uptake of radioactive iodide.
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What is the mechanism of action for radioactive iodide?
What is the usefulness of radioactive iodide? |
It emits Beta- Particles that are toxic thereby inducing selective destruction of the thyroid.
Low Dose - Used diagnostically to test thyroid function High Dose - First line for hyperthyroidism and an alternative to surgery. |
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What are the adverse effects of Radioactive iodide?
How are these adverse effects managed? |
Too much can kill follicular cells and induce hypothyroidism.
To manage possible acute hypothyroidism, T3 is given. |
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Who should this treatment be avoided in?
What else should be given (especially in thyroid cancer patients) before administering radioactive iodide? |
Children
Pregnant women TSH - Increases the uptake of radioactive iodide. |
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Name the 2 Thioamines.
What is the mechanism of action for these drugs? |
Propylthiouracil
Methimazole They compete with TG for oxidized Iodide. |
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What is the limitation to Thioamines?
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They effect is delayed
They affect the synthesis but not secretion If you inhibit thyroid hormone secretion too much, TSH will rise and can cause goiter. If hyperthyroidism persists past Thioamines, give radioactive iodide or resect thyroid gland. |
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What are 3 common adverse effects of Thioamines?
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Pruritic Rash
Arthralgia Increased tendency to bleed |
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What is a common adverse effect of these compounds?
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They are used in radiocontrast studies and can cause hypothyroidism.
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Inhibitors of organification and hormone release: Iodides and Thioamines. How do iodides work?
|
They work via the Wolff-Chaikoff effect, whereby they decrease NIS expression. This reduces the transcription of thyroid peroxidase and reduces iodination of TG by reducing Hydrogen Peroxide generation.
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What is the drawback?
What is the major indication for this drug class? |
The effects are transient.
It is primarily used short-term before surgical resection to reduce the vascularity of the gland. |
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How was this drug class used during the Chernobyl accident?
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People were given inorganic iodide to prevent the uptake of radioactive iodide.
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What is the mechanism of action for radioactive iodide?
What is the usefulness of radioactive iodide? |
It emits Beta- Particles that are toxic thereby inducing selective destruction of the thyroid.
Low Dose - Used diagnostically to test thyroid function High Dose - First line for hyperthyroidism and an alternative to surgery. |
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What are the adverse effects of Radioactive iodide?
How are these adverse effects managed? |
Too much can kill follicular cells and induce hypothyroidism.
To manage possible acute hypothyroidism, T3 is given. |
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Who should this treatment be avoided in?
What else should be given (especially in thyroid cancer patients) before administering radioactive iodide? |
Children
Pregnant women TSH - Increases the uptake of radioactive iodide. |
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Name the 2 Thioamines.
What is the mechanism of action for these drugs? |
Propylthiouracil
Methimazole They compete with TG for oxidized Iodide. |
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What is the limitation to Thioamines?
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They effect is delayed
They affect the synthesis but not secretion If you inhibit thyroid hormone secretion too much, TSH will rise and can cause goiter. If hyperthyroidism persists past Thioamines, give radioactive iodide or resect thyroid gland. |
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What are 3 common adverse effects of Thioamines?
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Pruritic Rash
Arthralgia Increased tendency to bleed |
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What are 3 key differences between proplythiouracil and Methimazole in their effects?
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Propylthiouracil inhibits thyroid peroxidase and peripheral conversion of T4 to T3
Methimazole only inhibits thyroid peroxidase. Methimazole is dosed less frequently and better tolerated It is therefore recommended for Graves Disease EXCEPT in pregnancy, Lactation, and Thyroid Storm (PTU works more quickly) |
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After giving a Thioamine, what kind of followup is necessary? Why?
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Their WBC's must be assessed (immune system is suppressed), as well as for fever or sore throat. These are indications of agranulocytosis, a rare and lethal complication.
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Why is it necessary to inhibit peripheral conversion of T4 to T3 when you are also giving the patient agents that will decrease hormone output?
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The agents that decrease hormone output have a delayed effect because of the large about of pro-hormone stored in the thyroid gland. Inhibition of peripheral conversion treats symptoms.
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What are the two Beta Blockers commonly used to inhibit peripheral conversion? What is each one indicated for?
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Esmolol - Treatment of thyroid storm
Propanolol - Acute hyperthyroid crisis To reduce Beta adrenergic like symptoms (sweating, tremor, tachycardia) |
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What 3 classes of drug can effect thyroid homeostasis?
Describe each of their actions briefly. |
Lithium - Inhibits T4/3 synthesis
Amiodarone - Have both inhibitor and stimulatory effects Corticosteroids - Inhibit 5-deiodinases leading to decreased T4-T3 conversion, increased T4, decreased T3 and increased TSH. |
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What 4 things can cause low TSH levels?
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Self administration of excess T4
Dopamine High dose glucocorticoids Decreased TBG |
