Pharm 2 - Endocrine 2

drraythe's version from 2015-11-09 15:40

Moore's Worksheet 2

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 & T4 (& rT3 but no one cares)
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 w/ Peroxidase as the catalyst
(2) Tyrosine, an amino acid, is processed by the ER & Golgi to become Thyroglobulin precursor
(3) In the lumen Iodination & 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 & 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 & DIT, what linkages form T4, T3 & rT3? If applicable know in which order they attach(Mono-Iodo-Tyrosine, Di-Iodo-Tyrosine)
(T4) DIT+DIT & has 4 Iodines (Double-D likes to do things 4 times over)
(T3) MIT+DIT & has 3 Iodines
(rT3) DIT+MIT & has 3 Iodines
(3 likes to MIX it up, like start w/ making out & then dick, or, go in REVERSE & Dick & 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 & location)?Type1: Converts T4 to T3 in serum & is located in the liver & kidneys (1 has good priorities, he knows the serum is important & he focuses on the big organs)
Type2: Converts T4 to T3 intracellularly (local) & is located in the pituitary, brain & brown fat (2 is about emotions → pituitary & brain & is brown)
Type3: Converts T4 to reverse T3 (inactive) (3 does everything backwards)
What is the ½ life of T4 & T3 in humans & dogs?(T4) Humans = 6 days. Dogs = 8-16hrs
(T3) Humans = 1 day. Dogs = 5-6 hrs
(3 is less than 4 & 3 lasts less than 4) (Or, humans is T4 6days & T3 1 day. Dogs is T4 8-16hr & T3 is 5-6hrs)
What percent of T3 is from T4?80%
Which Thyroid hormone has the greatest physiologic 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. & 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 Globulin (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 that are protein bound in human & in dogs?HUMANS: T3 = 99.8%, T4 = 99.98%
DOGS: T3 = 99% T4 = 99%
What is Cretinism?Thyroid deficiency resulting in retardation (physical & mental stunting)
What are the calorgenic effects of Thyroid hormone? (3)↑ IN METABOLISM
(1) ↑ in ATP formation via ↑ in Na/K ATPase activity
(2) ↑ in body temp
(3) ↑ 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) ↑ heart rate
(2) ↑ contractility
(3) ↑ BP in cats
(4) ↑ oxygen consumption that leads to ↑ tachypnea
(CATS) → HypERthyroid cats have ↑ Thyroid hormones which leads to ↑ systemic blood pressure & 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 ↓ Thyroid levels affect reflexes? (4)(1) Slower reflexes due to ↓ 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 fluffy & a dumb expression....that sucks)
What are some potential GI effects of HypOthyroid?↓ GI MOTILITY → Constipation & Diarrhea
What are reproductive effects of ↓ Thyroid hormone? (Male & female)Male: Testicular atrophy, ↓ libido & sperm production, infertility
Female: Absent or irregular reproductive cycles, infertility, abortion & poor litter survival rate
What are 2 types of HypOthyroidism? What are their czs?(1) 1⁰ HypOthyroidism: Autoimmune, idiopathic atrophy of Thyroid gland
(2) 2⁰ 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 PTx on Thyroxine?1-2x/year
What is the most common cz of HypERthyroidism in cats?Thyroid adenoma
How does Methimazole ↓ Thyroid synthesis?It is a reversible Anti-Thyroid agent. It inhibits the iodination & coupling of Thyroglobin. (The high from METH wont last forever, but it will stop you coming together w/ people (if you are Iodine & they are Thyroglobin) )
Why would it be a good idea to reversibly Tx HypERthyroidism initially?To see how well the kidneys are going to fxn when you suddenly ↓ the blood pressure (& thus their perfusion pressure)...If reversible, you can save kidneys if poor rxn to ↓ BP
If dispensing any transdermal drug what is important to tell the client?Wear gloves!!!
Can you distinguish between (127) I- & (131) I-?Thyroid follicle cells cannot distinguish between the 2 Iodine ion isotopes. (used to tx HypERthyroidism bc radiation destroys the cells)
What are some concerns w/ surgical Thyroidectomys?There can be Ectopic Thyroid tissue, which czs the HypERthyroidism. Also you can destroy the Parathyroid gland.
A diet low in ___ may be therapeutic for cats w/ HypERthyroidism.Iodine