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18 Cards in this Set
- Front
- Back
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Thyroid hormone effects
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- nearly every organ system
- disorders have profound effects on entire body function |
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Thyroid biosynthesis
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- iodinde from blood inot thyroid follicle
- peroxidase incorporates iodide into tyrosie residues - T3 and T4 stored in follicle cells - protease enzyme releases T4 and T3 from thyroglobulin protein into circulation - T4 converted to active T3 by deiodination in the liver and kidney |
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Hypothyroidism
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- autoimmune (hashimoto's)
- gioterogens - iodine deficiency - drug induced - radiation/thyroidectomy - congenital - dyshormonogenesis - secondary (TSH deficit) THIS WILL DECREASE BASAL METIbOLIC RATE AND DECREASE GROWTH |
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Hyperthyroidism
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- Graves disease
- toxic nodular goiter - subacute thyroiditis = this will increase basal metabolic rate and increase beta-adrenergic activity |
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Drugs used in Hypothyroidism
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- L-thyroxine (t4)
- Triiodothronine (T3) - Liothyronine - Levothyroxine?? |
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Drugs used in Hyperthyroidism
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- 131 I
- Thioamides, PTU, Methimazole - K iodine - Propranolol |
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Rationale to Tx of hypothyroidism
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- long term needed
- T4 usually most appropriate - dose changes made slowly - physiologic doses cna mimic hyperthyroidism |
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Levo-thyroxine
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- most suitable prep for tx of hypo
- long half life - low cost - converted to T3 and easy to monitor in the serum - no immediate CV effects |
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Liothronine (triiodothyronine)
T3 |
- active hormone
- more potent - immediate CV effects - may use this acutely and then switch to Levo |
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Rationale of Hyperthyroidism drugs
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- destroy hyperactive cells or directly inhibit thryoid hormone syntheisis/release
- thioamide drugs, 131 I, K iodide |
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Thioamide Drugs
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- Methimazole
- Propylthiouracil (PTU) |
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Mechanism of Thioamide drugs
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- directly inhibit peroxidase enzyme in T4/T3 biosynthesis
- PTU also inhibits deiodination of T4 to T3 in the liver. Thus, blood levels of T3 decline more rapidly than T4 |
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Effects and Toxicity of Thioamide drugs
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- slow onset, takes 2-4 weeks to become euthyroid
- well tolerated, may see skin rash |
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Radioactive Iodine
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- Tx of hyper
- active uptake exclusively into follicle cells - this allows localized tissue destruction - caution with elderly and children, pregnant - Complications= transient hyperthyroidism, permananent HYPO thyroidism |
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Potassium Iodide (KI)
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- tx of hyper
- paradoxical inhibition of iodine uptake, peroxidase enzyme, and proteolytic release of T4-3 - KI is only drug that inhibits release!!! - only has short term effect |
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Propranolol
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- tx of hyper
- symptomatic control of excessive B-adrenergic action - also inhibits T4 to T3 conversion in liver - ALSO controls symptoms of hyperthyroidism |
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Iodinated Radiocontrast Media (Ipodate)
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- tx of hyper
- inhibits T4 deiodination rapidly decreasing T3 concentrations |
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New Directions
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- Combinations of agents used for long term effect
- using immunosupressive agents -Exophthalmus- not sure what this is about |
