Term
| What are the steps in thyroid hormone synthesis? |
|
Definition
| Active uptake of iodide, Incorporation into Thyroglobulin by thyroidal peroxidase, Thyroglobulin molecule contains T4,T3,T2 and T1, TSH stimulates proteolysis of Thyroglobulin molecule into secreted T3 and T4 |
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Term
| What happens to T3 and T4 once in the blood stream? |
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Definition
| Both are avidly bound to plasma proteins some T4 is converted to T3 |
|
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Term
| What enzyme is responsible for incorportation of Iodide to the Thyroglobulin molecule? |
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Definition
|
|
Term
| How much of the circulating T3 is actually converted from T4? |
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Definition
|
|
Term
| What reaction converts T4 to T3 peripherally? |
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Definition
|
|
Term
| What enzyme is responsible for the Deiodization of T4 to T3 and where does it occur? |
|
Definition
| 5'deiodinase found mainly in the Kidney and Liver |
|
|
Term
| What is the fate of T3 and T4? |
|
Definition
| They are both conjugated with Glucuronic and Sulfuric Acid which is secreted in the bile |
|
|
Term
| How are T3 and T4 excreted? |
|
Definition
| They are conjugated with Glucuronic acid and Sulfuric Acid which are released into the BIle in the lIver |
|
|
Term
| What is the MOA of Perchlorate and Thiocyanate? |
|
Definition
| Blocks active Iodidne uptake by the Thyroid Gland |
|
|
Term
| Which drugs inhibit thyroidal peroxidase? |
|
Definition
| Iodides, Propylthiouracil and Methimazole |
|
|
Term
| Does Iodide inhibit the secretion of Thyroid Hormone? |
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Definition
|
|
Term
|
Definition
| Beta-Blockers, Propylthiouracil and Corticosteroids inhibit?,5'Deiodinase |
|
|
Term
| What drug blocks both Thyroidal Peroxidase and 5'Deiodinase? |
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Definition
|
|
Term
|
Definition
|
|
Term
| What is Triiodothyronine? |
|
Definition
|
|
Term
| What is the result of deiodinization of T4 at the 5' position? |
|
Definition
|
|
Term
|
Definition
|
|
Term
| What is the result of 5'-deiodinase-1 on T4? |
|
Definition
| Converted into active T3 which is more potent that T4 |
|
|
Term
| How much more potent is T3 than T4? |
|
Definition
| 5-10x, T4 is often considered a prohormone |
|
|
Term
| What enzyme is responsible for the conversion of T4 into T3 in the liver? |
|
Definition
|
|
Term
| What is the effect of TSH on thyroid release of T3 and T4? |
|
Definition
|
|
Term
| Which Hormone caused decreased T3 and $ secretion? |
|
Definition
| Somatostatin from the Hypothalamus |
|
|
Term
| Is TSH kept in relatively constant concentrations throughout the day? |
|
Definition
|
|
Term
| What do Thyroid Hormones regulate? |
|
Definition
|
|
Term
| What effect does Thyroid Hormone have on O2 consumption and Protein Synthesis? |
|
Definition
|
|
Term
| What are the two thyroid hormones recepter found in a heterocomplex? |
|
Definition
| Thyroid Hormone Receptor and the Retinoid X Receptor |
|
|
Term
| Are thyroid Horomones bound to binding proteins in circulation? |
|
Definition
|
|
Term
| Where are the Thyroid Receptors located? |
|
Definition
|
|
Term
| What is the kinetics of Thyroid Hormone effect activation? |
|
Definition
| Slow onset and Slow Offset due to work in the Nucleus |
|
|
Term
| What are some causes of hypothyroidism? |
|
Definition
| Hashimotos, Radiation, Congenital, Iodine Def., Drug Induced |
|
|
Term
| What drug reduces TSH secretion causing Hypothyroidism? |
|
Definition
|
|
Term
| What drugs can inhibit Thyroid Hormone release? |
|
Definition
| Iodine itself, Amiodarone and Lithium |
|
|
Term
| How do bile resins such as Colestyramine cause hypothyroidism? |
|
Definition
| They can bind Thyroxine making it less bioavailable |
|
|
Term
| What drugs can inhibit peripheral conversion of T4 to T3 causing hypothyroidism? |
|
Definition
| Glucocorticoids and Beta-blockers |
|
|
Term
| What is the gold standard for treating hypothyroidism caused by anything other the drug induced? |
|
Definition
| Synthroid-Synthetic Thyroxin (T4) |
|
|
Term
| What is the problem with Synthroid? |
|
Definition
| It is inherently unstable when exposed to heat or light |
|
|
Term
| What is the main side effect associatted with Synthroid? |
|
Definition
| Cardiac Dysarthrythmias cause by the beta-adrenergic response |
|
|
Term
| What treatment is associatted with an increase in HR |
|
Definition
| Sweating, and Tremors?,Synthroid |
|
|
Term
| What can the increased cardiac work caused by over medication with Synthroid lead to? |
|
Definition
| Increased work leads to increased oxygen demands and if not met can turn into Angina |
|
|
Term
| What is the most senstive way to check Synthroids activity as you prescribe it? |
|
Definition
| Monitor TSH levels, also ask the patient how they feel |
|
|
Term
| A 45 year old is taking I-thyroxine following her thyroidectomy. Her physician tells her to take the medications at a different time of the day than one of her other medications. The most likely reason for this is: |
|
Definition
| The INtestional absorption of I-Thyroxine can be quite variable and is affected by certain medications |
|
|
Term
| What is a common cause of Hyperthyroidism? |
|
Definition
|
|
Term
| What types of drugs are used to treat hyperthyroidism? |
|
Definition
| Ionic Inhibitors, Iodine containing compounds |
|
|
Term
| What is the MOA of Lugol's Solution? |
|
Definition
| It is an Iodide containing compound which is concentrated in the Thyroid and prevents Thyroid Hormone Secretion |
|
|
Term
| What is Lugol's solution composed of? |
|
Definition
| 5% iodine and 10% potassium iodine |
|
|
Term
| What drug is used priot to a thyroidectomy or to prevent the uptake of radioactive Iodine by the thyroid? |
|
Definition
|
|
Term
| How long does the preventative effects of Lugols Solution last? |
|
Definition
| Short lived due to gland escaping inhibiton after a couple weeks |
|
|
Term
| What is radioactive iodine 131 used to treat? |
|
Definition
| Hyperthroidism,It destroys the Tyroid Gland by Beta Radiation |
|
|
Term
| How is Radioactive Iodine dosed? And can it be used while pregnant? |
|
Definition
| Given as a single dose of 5-15 millicuries, and No not used in pregnancy |
|
|
Term
| Why is radioactive iodine not used in pregnant women? |
|
Definition
| It will cross the placenta and be concentrated in the Fetal Thyroid causing its destruction |
|
|
Term
| What percentage of patients given radioactive iodine wind up with Hypothyroidism? |
|
Definition
| 80% and 20% of those will require thyroid hormone supplementation |
|
|
Term
| Why is radioactive iodine only prescribed to patient over the age of 35? |
|
Definition
| There is a concern that patients will develop cancer later in life |
|
|
Term
| What are the tow thionamides? |
|
Definition
| Propylthiouracil and Methamizole |
|
|
Term
|
Definition
| Propylthiouracil and Methamizole work to treat hyperthyroidism?,Inhibit Thyroid Peroxidase |
|
|
Term
| What other enzyme can Propylthiouracil inhibit causing a double effect? |
|
Definition
| 5'thiodinase-1 which converts T4 to T3 |
|
|
Term
| What drugs can reduce thyroid immunity which can lead to a remission of Graves disease and removal of medication? |
|
Definition
| Propythiouracil and Methamizole |
|
|
Term
| What are the side effects of the Thionamides? |
|
Definition
| Rash, Fever, Arthralgia, and agranulocytosis |
|
|
Term
| Which drug can cause a serious agranulocytosis? |
|
Definition
| The Thionamides, Propylthiouracil and Methamizole |
|
|
Term
| Does Propylthiouracil cross the placenta or into breast milk? |
|
Definition
| No so can be used during pregnancy |
|
|
Term
| What drug is the 3rd leading cause of drug induced liver failure? |
|
Definition
|
|
Term
| What is a less hepatotoxic option than Propylthiouracil? |
|
Definition
| Methimazole, it will only cause reversible jaundice |
|
|
Term
| When is Propythiouracil use warranted? |
|
Definition
| During a Thyroid storm brough about by 5'deiodinase-1 or during pregnancy |
|
|
Term
| Which drugs can lead to remission and removal of medication for a hyperthyroidism patient? |
|
Definition
| Prophylthiouracil or Methimazole |
|
|
Term
| What is the Beta-antagonist used for treatment of hyperthyroidism? |
|
Definition
|
|
Term
| Why do the Thionamides take a few weeks to become effective? |
|
Definition
| The thyroid has a couple week supply of thyroid hormone it can continue to secret |
|
|
Term
| What are the symptoms of hyperthyroidism? |
|
Definition
| Tremors, anxiety, palpatations and a racing heart |
|
|
Term
| Which drug can immediately eliminate some of these symptoms? |
|
Definition
| Propanolol which blocks the sympathetic effects of Hyperthyroidism |
|
|
Term
| When should use of Propanolol be discontinued? |
|
Definition
| After the couple week store of Thyroid hormone is used up and Thionamides can take effect |
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