Pharm- Thyroid and Anti-thyroid

kelseyfmeyer's version from 2015-04-16 18:49


Question Answer
In the Hypothalamic Pituitary Thyroid Axis what does each secrete?Hypothalamus secretes Thyroid Releasing Hormone (TRH). Pituitary secretes Thyroid Secreting Hormone (TSH). Thyroid secretes T3 and T4
Thyroid hormone has a negative feedback on what?Thyroid hormones have direct or indirect negative feedback on TRH/TSH release
What are the 6 steps in thyroid synthesis?[NOTE: all these steps are stimulated by TSH] (1) Iodine from blood enters follicular cell by active transport mechanism. In the lumen iodine is converted to iodide. peroxidase is the catalyst (2) Tyrosine ,an amino acid, is processed by the ER and Golgi to become Thyroglobulin precursor (3) in the Lumen Iodination and coupling of the Thyroglobulin precursor occurs. Peroxidase is the catalyst. (4) Thyroglobulin after pinocytosis reenters the follicular cell as colloid droplets. (5) proteases convert Thyroglobulin into either T3, T4, MIT (mono-iodo-tyrosine), or DIT (Di-iodo-tyrosine). (6) T3 &T4 droplets leave the follicular cell into the blood. MIT and DIT are reused by the follicular cell to make more Thyroglobulin.
What is thyroid hormones backbone?Thyroid hormone structure is based on 2 tyrosine molecules connected by an ether linkage
In relationship to MIT and DIT, what linkages form T4, T3 and rT3? If applicable know in which order they attach(mono-iodo-tyrosine, Di-iodo-tyrosine) (T4) DIT+DIT and has 4 iodines (Double-D likes to do things 4 times over) (T3) MIT+DIT and has 3 iodines. (rT3) DIT+MIT and has 3 iodines (Three likes to MIX it up, like Start with making out and then dick, or, go in REVERSE and Dick and THEN making out)
What is the main thyroid hormone secreted by the thyroid gland?T4
T4 is a pro-hormone for T3. What is the main enzyme that catalyzes this?T4 is deiodinated to T3 by iodothryonine 5’ – deiodinase
How do the 3 types of iodothyronine 5’-deiodinase differ (action and location)?(type1) Converts T4 to T3 in serum, and is located in the liver and kidneys (1 has good priorities, he knows the serum is important and he focuses on the big organs) (Type2) Converts T4 to T3 intracellularly (local) and is Located in the pituitary, brain and brown fat.(Two is about emotions->pituitary and brain, and is brown) (Type3) Converts T4 to reverse T3 (inactive) (Three does everything backwards)
What is the ½ life of T4 and T3 in humans and dogs?(T4) Humans= 6 days. Dogs= 8-16hrs. (T3) Humans= 1 day. Dogs= 5-6 hrs (Three is less than 4, and 3 lasts less than four) (Or, humans is T4 6days and T3 1 day. Dogs is T4 8-16hr and T3 is 5-6hrs)
What percent of T3 is from T4?80%
Which thyroid hormone has the greatest physiology activity? By how much?T3 has the greatest physiological activity. T3 has 4 times as much activity as T4. (Three is much more active than 4...makes sense, he has legs that work. And go fig that 3 has 4 times...bc that's not confusing)
What is the role of rT3?Has no physiological activity
Why do thyroid hormones in humans have a longer half-life?Humans have a higher percentage of their circulating thyroid hormones bound to plasma proteins as compared to dogs.
What are the 3 proteins that bind to thyroid hormones?(1) Thyroxine Binding Gloubulin (TBG) (2) Thyroxine binding prealbumin (3) Albumin
Which protein do humans have 4x as much of compared to dogs?TBG (thyroxine binding globulin)
What are the percentages of thyroid hormones protein bound in human and in dogs?(HUMANS): T3=99.8%, T4=99.98%. (DOGS): T3=99% T4=99%
What is Cretinism?Thyroid deficiency resulting in retardation (physical and mental stunting)
What are the calorgenic effects of thyroid hormone? (3)INC IN METABOLISM--> (1) Increase in ATP formation via increase in Na/K ATPase activity (2) Increase in body temperature (3) Increase in oxygen consumption
Would a hypothyroid dog more likely be found in the sun or shade?Sun--> heat seeking!
What are thyroid hormones effects on the CVS? (4) How does this relate to hyperthyroid cats?(1) inc heart rate (2) inc contractility (3) inc BP in cats (4) Increase oxygen consumption that leads to increased tachypnea. (CATS)--> Hyperthyroid cats have increased thyroid hormones which leads to increased systemic blood pressure and renal perfusion pressure
Would a hypothyroid dog have high or low serum cholesterol?high (why theyre usually fat?)
How would low thyroid levels affect the skin? (4)(1) Bilateral alopecia (2) Follicle atrophy (3) Myxedema--> puffy appearance, thickened skin folds above the eyes (4) Tragic facial expression due to upper eyelids drooping
How would low thyroid levels affect reflexes? (4)(1) Slower reflexes due to decreased conduction velocity in CNS (2) lethargy (3) Myopathy (4) Facial Nerve paralysis
Could facial nerve paralysis be a result of a thyroid disorder?yes (all fuffy AND a dumb expression....that sucks)
What are some potential GI effects of hypothyroid?DEC GI MOTILITY---> constipation, diarrhea
What are reproductive effects of dec thyroid hormone? (male and female)(male:) Testicular atrophy, decreased libido and sperm production, infertility. (female:) absent or irregular reproductive cycles, infertility, abortion and poor litter survival rate
What are 2 types of hypothyroidism? What are their causes?(1) Primary Hypothyroidism: Autoimmune, idiopathic atrophy of thyroid gland (2) Secondary Hypothyroidism: destruction of thryotophs in pituitary gland by tumor
Which replacement thyroid hormone is used in dogs?T4 --> L-Thyroxine (doggie 4 a good home)
Serum T4 levels should be checked how often in patients on Thyroxine?1-2x/year
What is the most common cause of hyperthyroidism in cats?thyroid adenoma
How does methimazole decrease thyroid synthesis?It is a reversible anti-thyroid agent. It inhibits the iodination and coupling of thyroglobin. (the high from METH wont last forever, but it will stop you come coming together with people (if you are iodine and they are thyroglobin) )
Why would it be a good idea to reversibly treat hyperthyroidism initially?To see how well the kidneys are going to function when you suddenly lower the blood pressure (and thus their perfusion pressure)...If reversible, you can save kidneys if poor reaction
If dispensing any transdermal drug what is important to tell the client?wear gloves!!!
Can you distinguish between (127)I- and (131)I-?Thyroid follicle cells cannot distinguish between the two. (used to tx hyperthyroidism bc radiation destroys the cells)
What are some concerns with surgical thyroidectomys?There can be ectopic thyroid tissue, which causes the hyperthyroidism. Also you can destroy the parathyroid gland.
A diet low in ____ may be therapeutic for cats with hyperthyroidism.Iodine

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