Physio 2 - Endocrinology 3

drraythe's version from 2015-06-09 01:45

Thyroid gland

Question Answer
thyroid tissue consists of _________Follicles
what does a thyroid follice consist of? (2)(1) thyroid cells in a single layer= hormone producing cells, the height of the cell layer indicates level of activity (2) colloid= hormone STORAGE form, final stage of hormone synthesis
what does the thyroid need to make hormones? (#1 ingredient). How does the thyroid GET it?IODINE, active pump for uptake into cell
How is a thyroid hormone synthesized/released? (lengthy one) (8)(1) iodine uptake via active pump (2) synth/exocytosis of thyroglobin (TGB) (3) oxidation of iodide to iodine via perioxidases and secretion of iodine into colloid. (4) iodination of tyrosines of TGB via iodinase, form monoiodotyrosine (T1) and Di-iodotyrosine (T2) (5) condensation of T1+T2 into T3 (tri-iodotyrosine) and T4 (tetra-iodotyrosine)= coupling= storage form containing ~30 T4 and a few T3 (6) endocytosis of TGB (thyroglobin) and proteolytic cleaving via lysosomal enzymes (7) release of T4 (93%) and T3 into circulation (8) lipophilic T4+3, so bind to plasma proteins (99%)
to what does T3 and T4 bind to in the blood? at what affinity does it bind?to Thyroxin-binding protein (and albumin), 99%
what is the half life of T4 in dogs? man?Dogs= 12-14hrs Man=6 days
at the end of synth and release, where is T1, T2, T3, T4, TGB, iodine, and amino acids?T3+T4 bind to thyroxin binding protein in blood. T1,T2, and TGB stay in thyroid cell. Iodine and AAs are recycled
what did she emphasize about the thyroid hormone synth and release slide?Good places to interfere are at the ENZYMATIC STEPS (pump mechanism, peroxidation)
How is a thyroid hormone synthesized/released? (brief one) (8)(1) iodide trapping (2) synth of TGB (3) oxidation of iodide (4) iodination of tyrosine (5) Coupling of T1 and T2 (6) pinocytosis and digestion of colloid (7) secretion of thyroid hormones (8) xport in blood
What is TGB? composed of what?thyroglobin, an intermediate in making thyroid hormones, it is composed of ~70 tyrosine AAs
**how are thyroid hormones controlled?via the hypothalamic-pituitary-thyroid axis
what is TRH stimulated by? Inhibited by? (outside of the body)(Thyrotropin releasing hormone in the hypo) stimulated by COLD and inhibited by STRESS (sympathetic n.s.)
TSH stims thyroid gland to synth and secrete thyroid hormones through (4 things the TSH stimulates in the process)(1) stim of iodide pump (2) stim of iodination of tyrosine (3) stim of TGB(thyroglobin) proteolysis (4) stim of growth of thyroid cells (can lead to thyroid enlargement)
how is release of TSH controlled?inc levels of circulating thyroid hormones inhibit further release of TSH (by dec TRH receptor number)
describe the T3/T4 levels in a well regulated systemthey are nearly constant but influenced by ambient temperatures
if the climate is cold, what happens to the thyroid hormone levels?theyre higher
how does T3/T4 get into target cells?DIFFUSE (lipophilic)
once in the target cell, what do T3/4 do?T4 converted into T3, T3 binds to nuclear receptors and activates transcription of genes
**thyroid hormones activate xscription of genes which does what? (2)(1) stim synth of many enzymes, structural+xport proteins (2) generalized inc of many metabolic activities in many tissues
Deactivation and excretion of thyroid hormones?T3 is deactivated by peripheral tissue de-iodinases and excreted via liver after conjugation with glucoronic acid
which thyroid hormone is the active one?T3 (threes at the gym)
**What do thyroid hormones DO?regulate basic metabolic activity of most tissues and ensure that fuel is available
what does thyroid hormone do to carb metabolism?**geared towards supplying glc for energy (inc glc absorption/uptake, inc glc utilization for energy, inc glc production)
what does thyroid hormone do to lipid metabolism?**geared towards supplying fat for energy (inc lipolysis, inc beta oxidation, inc bile secretion->lowers blood chlosterol)
what does thyroid hormone do to protein metabolism?NORMAL GROWTH depends on thyroid hormones so PROTEIN ANABOLIC (will turn catabolic in excess situations or in adults)
what does thyroid hormone do to basal metabolism?INC METABOLIC RATE! inc nutrition utilization, inc ATP formation, inc O2 consumption, inc heat production
What does a thyroid hormone excess (everything stim) do to the CNS?inc rapidity of cerebration, dissociation= NERVOUSNESS, excitability, anxiety, insomnia
What does a thyroid hormone excess (everything stim) do to the growth/BW of a young animal?accelerates growth, but epiphyses close early--> stunted, heavy body
What does a thyroid hormone excess (everything stim) do to the growth/BW of an adult animal?weight loss (catabolic)
What does a thyroid hormone excess (everything stim) do to the circulatory and resp system?Tachycardia, hypertension, tachypnea
what does a thyroid hormone deficiency (everything slowed) do to the CNS?lethargy, somnolence
what does a thyroid hormone deficiency (everything slowed) do to the growth/body weight of a young animal?retards CNS and body growth-> CRETINISM
what does a thyroid hormone deficiency (everything slowed) do to the growth/body weight of an adult animal?weight gain
what does a thyroid hormone deficiency (everything slowed) do to the skin?follicle atrophy -> bilateral alopecia, myxedema, pigmentation
When you think HYPERthyroidism, you think of what animal?CATS (middle aged-->old)
main cause of hyperthyroidism in cats?Mostly benign thyroid tumors secreting T4/T3= ADENOMAS (in ppl it's autoimmune, antibodies w/ TSH effect)
hyperthyroidism in cats symptoms for weight, mm, and liver?weight loss, mm weakness/wasting, mild fatty liver syndrome
hyperthyroidism in cats symptoms for appetite?normal to increased
hyperthyroidism in cats symptoms for nervous system stuff?hyperactive, nervous, anxiety (10% cats apathetic)
hyperthyroidism in cats symptoms for body heat/tolerance?heat intolerance, inc temp
hyperthyroidism in cats symptoms for heart? eye?tachycardia, hypertension--> retinal detachment
hyperthyroidism in cats symptoms for poop/pee/drinkingdiarrhea, polyuria/polydipsia (b/o medullary washout aka osmotic gradient messed up)
hyperthyroidism in cats symptoms for skin?matted hair or alopecia b/o b/h changes
hyperthyroidism in cats symptoms for overall metabolism?accelerated meta and fxn
If i say hypothyroidism, you think what animal?dogs (middle aged to old)
definition of hypothyroidism?insufficient production/ secretion of thyroid hormones
main causes of hypothyroidism in dogs?most deficits of the thyroid gland (autoimmune, lymphocytic, infiltration, or idiopathic atrophy)
hypothyroidism in dogs symptoms of skin?MOST COMMON. Dry, alopecia, flaking or seborroea, pigmentation, myxedma
what is myxedema? (what, where, result)accumulation of hyaluronic acid in face and tail (sometimes nerves)...edema!
hypothyroidism in dogs symptoms of activity level? weight? temperature?lethargy, weight gain+exercise intolerance, heat seeking (b/c cold)
hypothyroidism in dogs symptoms of repro system?dysfunction
hypothyroidism in dogs symptoms of overall metabolismdec meta and fxn
What is the definition of a goiter?non-neoplastic hyperplasia of thyroid gland (this can be used for any thyroid gland enlargement sometimes tho)
what cause a goiter? (2)(1) dietary iodine deficiency*** (2) goitrogenic substances. eg) progoiten in soy beans/cabbage/rapeseed (conversion of goitin in the GI, interferes with iodine pump) ((pesticides will also case goitrogenic effects)
Pathogenesis of a goiter?iodine deficient--> thyroid hormone decreases-->stimulates TRH/TSH release--> stim thyroid cell growth--> gland enlargement=== compensatory gland hyperplasia
what happens to offspring of hypothyroid parents?can be still-born or develop hypothyroidism (cretinism, retarded growth)
what species can goiters affect?formerly common in all species in iodine deficient areas, but rare b/o dietary supplementation now. Seen in BIRDS and occasional large animals
what is a test we can do to detect hyperthyroidism cause in cats?inject radioactive iodine-analog, look for super lit up area= the tumor