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Thyroid Pharmacology - Bansal
Terms in this set (17)
Thryoid Pharmacology is centered on these three purposes
1. Replacement therapy in hypothyroidsim
2. Decrease circulating thyroid hormone levels in hyperthyroidism
3. Treat acute symptoms of hyperthyroidism
What two drugs can be used to replace thyroid hormone?
Levothyroxine -- T4 (preferred)
Liothyronine -- T3
We don't want to give T3 except when indicated because there is no regulation: We will flood system with free hormone and this is especially toxic to the cardiac tissue which is very sensitive to it. It will cause upregulation of Beta receptors.
- Taken orally
- preferred for long-term replacement therapy for hyperthyroidism
- has a long half-life (7 days)
- T4 administration allows tissues to activate it to T3 by physiologically regulated mechanisms
T3 in active form
has a short half-life
How can we treat someone in a Myxedema coma?
IV administration of T3 and T4 initially until patient is revived, then oral T4
Myxedema coma is an extreme form of a long-standing hypothyroidism usually in older people.
There are some conditions that require T4 dose adjustments
There is an INCREASED binding to TBG of T4 in pregnant women because of estrogens (also oral contraceptives) so we have to INCREASE dose if hypothyroid.
There is a DECREASED binding of T4 to TBG in the presence of glucocorticoids, androgens and acute and chronic illnesses
What about Hypothyroid pregnant women?
They need higher doses.
Treatment of Hyperthyroidism
2. Anti-Thyroid drugs that can inhibit iodine uptake, inhibit thyroid hormone synthesis, or inhibit TH release from thyroid
3. Medical destruction of Thyroid tissue with Radioiodine (I^131)
beta gamma particles destroy thyroid gland tissue. patients can become hypothyroid but we can manage this with T4.
Contraindicated in pregnancy and lactation
What about Propanolol? See slide 8.?????????
To treat hyperthyroidism/thyrotoxicosis, we can inhibit Thyroid hormone synthesis. We can do this with __________.
- inhibits thyroid peroxidase which blocks iodide oxidation. it also inhibits the peripheral deiodination of T4 to T3
- it is a thioamide and is safer than others so preferred in pregnancy
- serious side effect: Agranulocytosis
no neutrophils, patient prone to infections
Potassium Iodide can treat ________________.
It is a drug for hyperthyroidism but is not used for long-term management. It inhibits hormone release, iodination of Tyrosine and decreases the size and vascularity of the hyperplastic gland. However, the inhibition of iodination is only momentarily (Wolff-Chaikoff effect) as the effect is reversible.
It is used therapeutically for a thyroid storm and surgical preparation.
Contraindicated in pregnancy as it can cause a fetal goiter.
Beta-blockers can treat the symptoms of hyperthyroidism
What drugs can inhibit deiodination?
high doses of propyltiouracil, corticosteroids, beta-blockers
used in thyroid storm (acute release of large amounts of TH)
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