Pharmacology UT Tyler Exam 3 – Qs And As What helps with metabolism and calcitonin for regulating serum calcium ✔️Ans - Triiodothyronine (T3), Thyroxine (T4) What kind of feedback mechanisms regulate hormone secretion from the thyroid gland ✔️Ans - Negative feedback The hypothalamus releases ______ which stimulates the release of TSH from the pituitary gland ✔️Ans - thyrotropin releasing hormone (TRH) What does TSH stimulate the synthesis/release from the thyroid gland ✔️Ans - T3 and T4 What does excess free T3 and T4 inhibit the _____ which results in decreased TRH and TSH secretion ✔️Ans - hypothalamus-pituitary-thyroid (HPT) axis What is hypothyroidism? ✔️Ans - a decrease in thyroid hormone secretion which can have a -primary cause (thyroid gland disorder) *more frequent -secondary cause( lack of TSH secretion=pituitary disorder) -tertiary cause (lack of TRH=hypothalamus disorder) What indicates primary hypothyroidism ✔️Ans - Decreased T4 and elevated TSH levels Causes for _____ include acute or chronic inflammation of thyroid gland, radioiodine therapy, excess intake of antithyroid drugs or surgical removal of the thyroid gland ✔️Ans - primary hypothyroidism Myxedema is severe hypothyroidism in the adult where symptoms include ✔️Ans - -lethargy -apathy -memory impairment -emotional changes -slow speech -deep, coarse voice -edema of eyelids/face 1 / 4
-dry skin -cold intolerance -slow pulse -constipation -weight gain -abnormal menses (metabolic functions slow down) In children, hypothyroidism can have a congenital onset that can cause ✔️Ans - delayed physical and mental growth (cretinism) or onset may be prepubertal (juvenile hypothyroidism) Hypothyroidism is treated with drugs that contain ✔️Ans - T3 or T4 alone or in combination Exogenous thyroid hormones (ingestion of thyroid hormones) are contraindicated in patients with ✔️Ans - thyrotoxicosis, acute myocardial infarction (AMI), and adrenal insufficiency Elevated serum calcium levels could also be related to ____; exogenous ____ may also be prescribed ✔️Ans - hypothyroidism; calcitonin ______ is the drug if choice for replacement therapy for the treatment of primary hypothyroidism ✔️Ans - Levothyroxine sodium How does Levothyroixine sodium work ✔️Ans - It increases the levels of T4 and metabolically is deiodinated to T3 -it is also used to treat simple goiter and chronic lymphocytic (Hashimoto) thyroiditis (not quick fix, has to build up) Given b4 meals bc food absorption decrease absorption to the drug Liothyronine pharmodynamics ✔️Ans - -synthetic T3
-half-life: 2.5 days
-rapid onset of action (few hrs) -used as replacement or supplemental treatment for hypothyroidism of any etiology -UNlike levothyroxine, it does not need to be deiodinated= increases the availability for use by body tissues 2 / 4
-better absorbed from GI tract (95%)than Levothyroxine bc of its rapid onset of action and short half-life -initial therapy for treating myxedema -oral or IV administration Desiccated thyroid is a naturally occurring thyroid hormone from ✔️Ans - porcine thyroid glands. It contains both levothyroxine and liothyronine Desiccated thyroid is used to treat hypothyroidism due to ✔️Ans - thyroid atrophy, thyroid hormone deficiency, and goiter Liotrix is a mixture of levothyroxine sodium and liothyronine sodium in a ___ to ___ ratio by weight ✔️Ans - 4 to 1 For treating hypothyroidism there is no significant advantage to using liotrix over levothyroxine sodium alone because ✔️Ans - levothyroxine converts T4 to T3 in the peripheral tissues What is hyperthyroidism ✔️Ans - an increase in circulating T3 and T4 levels which results from an overactive thyroid gland or excessive output of thyroid hormones Hyperthyroidims may be mild, w few symptoms or severe as in ✔️Ans - thyroid storm, in which death may occur from vascular collapse The most common types of hyperthyroidism caused by hyperfunction of thyroid gland are ____ and ____. What are the characteristics? ✔️Ans - Graves disease and thyrotoxicosis -tachycardia -palpitations -excessive perspiration (hyperhidrosis) -heat intolerance -nervousness -irritability -bulging eyes (exophthalmos) -weight loss 3 / 4
Hyperthyroidism can be treated by ✔️Ans - surgical removal of a portion of the thyroid gland (subtotal thyroidectomy), radioactive iodine therapy, antithyroid drugs which inhibit the synthesis/release of thyroid hormone -any of these treatments can cause HYPOthyroidism Thiourea derivatives (thioamides) are the drug choice used to decrease thyroid hormone production. It works by ✔️Ans - blocking thyroid action -do NOT destroy thryroid tissue Propylthiouracil (PTU) and methimazole are effective thioamide antithyroid drugs and are used to ✔️Ans - -control overactive thyroid due to Graves disease toxic nodular goiter or multinodular goiter
- also used b4 radioiodine treatment of thyroid surgery
- goiter formation
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How is methimazole different from PTU ✔️Ans - -it does not inhibit peripheral conversion of T4 to T3 -10xs more potent -longer half-life euthyroid state is achieved in 2-4 mo.-preferred antithyroid bc less severe SE -rapidly absorbed from GI tract Prolonged use of thioamides may cause goiter bc of increased ____ secretion and inhibited ____ and ____ synthesis ✔️Ans - TSH; T4 and T3 Minimal doses of thioamides should be given when indicated to avoid ✔️Ans
Strong iodide preparations such as potassium iodide have been used to suppress thyroid function for patients who ✔️Ans - are undergoing subtotal thyroidectomy because of Graves disease Antithyroid drugs interact with many other drugs ✔️Ans - -used with oral anticoagulants (ex. warfarin)= increase in anticoagulation effect -decrease the effect of insulin and oral antidiabetics -digoxin and lithium increase the action of thyroid drugs