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1.11
Thyroid Hormones
| Term | Definition |
|---|---|
| Thyroid gland producing hormone 1 | triiodothyronine (T3) |
| Thyroid gland producing hormone 2 | tetraiodothyronine (T4) |
| Thyroid gland producing hormone 3 | calcitonin |
| 2 pathways of synthesis and processing of thyroid hormone: | 1. basolateral 2. apical |
| what activates the hypothalamic-pituitary-thyroid axis | exposure to cold may activate it |
| hypothalamic-pituitary-thyroid axis: TRH stimulates | release of TSH from pituitary thyrotropes. SST and dopamine inhibit it |
| what stimulates synthesis of hypothalamic-pituitary-thyroid axis | TSH and small amounts of iodide |
| what inhibits synthesis of hypothalamic-pituitary-thyroid axis | large amounts of iodine |
| T4 or thyroxine | most prevalent |
| T4 or thyroxine has high affinity for | plasma binding proteins |
| T3 | is the physiologically active form |
| Is T4 or T3 more potent? | T3 is 3-4x more potent |
| Reverse T3 | action-partial agonist |
| Thyroid hormone mechanism and effects | T3 (nuclear receptor) induces new proteins synthesis which produces effects of thyroid hormone |
| 2 disruptions of thyroid homeostasis: | hypothyroidism and hyperthyroidism |
| iodine deficiency and goiter cascade | low iodine, not enough to make T3/T4, low levels T3/T4, stimulate hypothalamus and pituitary for TRH and TSH secretion |
| TSH can promote _______ which causes goiter (irregular growth) | hyperplasia and hypertrophy of thyroid gland |
| hypothyroidism: treatment (thyroid hormone replacement therapy)--> Synthetic T4 (thyroxine) | synthroid |
| hypothyroidism: treatment (thyroid hormone replacement therapy)--> Synthetic T3 (liothyronine) | cytomel |
| hypothyroidism: treatment (thyroid hormone replacement therapy)--> "natural thyroid" | contains both T3 and T4 |
| hypothyroidism: thyroid hormone replacement ADR | instruct patients to watch for symptoms and notify PCP if they occur transient alopecia pseudotumor cerebri seizures |
| hypothyroidism: thyroid hormone replacement drug interactions | 1. increase effects of anticoagulants (monitor INR) 2. increase cardiac effects of sympathomimetics, tricyclic antidepressants (decrease dose) 3. blood glucose control drugs (may need to increase ) 4 decrease effects of beta blockers (increase dose) |
| hypothyroidism DRUG: Levothyroxine: patient counseling point | take on an empty stomach |
| hyperthyroidism-drug interaction with thyroid hormone biosynthesis: Thioamides | interfere directly with the synthesis of thyroid hormones |
| hyperthyroidism-drug interaction with thyroid hormone biosynthesis: Radioactive Iodine | damages gland via selective uptake followed by local radiation damage |
| hyperthyroidism-drug interaction with thyroid hormone biosynthesis: B-receptor ANTAGONISTS | control the manifestations, CCBs are alternative drug |
| Hyperthyroidism DRUG: Thioamides MOA | 1. prevents thyroid hormone synthesis by INHIBITING thyroid peroxidase (TPO) 2. Propylthiouracil inhibits peripheral deiodinase (converting T4 to T3) |
| Hyperthyroidism- Radioactive Iodine: most often used isotope | I(131)- emits beta particles (99%) and gamma rays (1%) |
| Hyperthyroidism-Radioactive iodine Beta particles (99%) | localized destructions, radioactive/chemical ablation (can destroy thyroid cells with little damage to surrounding tissues) |
| Hyperthyroidism DRUG: B-adrenergic Receptor ANTAGONISTS | Propranolol (INDERAL) |
| Hyperthyroidism DRUG: Propanolol (INDERAL) MOA (2) | 1. antagonizes the SNS symptoms 2. blocks periopheral conversion of T4 to T3 |
| Many symptoms of hyperthyroidism are associated with: | Sympathetic stimulation |
Created by:
megangodfrey97
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