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general Thyroid glan
introduction and terms of Thyroid gland/hormones
| Question | Answer |
|---|---|
| biolocical half-life | refers to the rate of elimination of biologically active substances (hormones) by 50% |
| calcitonin | hormone produced by parafollicular cells of thryroid, inhibits bone reabsorption by blocking PTH receptors on osteoclasts |
| cretinism | clinical condition caused by congeneital hypothyroidism or idodine deficency |
| exopthalmus | bulging eyes, sign of thryroid disease |
| goitre | visible or palpable enlargement of thyroid gland |
| hypothyroidism | abnormally low activity of thyroid gland with low circulating TH levels, caused by thyroid disease |
| osteopoerosis | term used for marked reduction in all components of bone mass |
| Thyroid releasing hormone | TRH, released by Hypo, and reaches AP by portal system. causes thyrotrophs to release TSH |
| two hormones of thyroid involved in metabolic activity of body | T4 and T3 (produced in follicular cells) |
| effect of T4 and T3 | increase metabolic rate |
| Primary controller of TH secretion | TSH secreted by AP |
| What are the percentages of TH secreted by thyroid gland | 93%T4 adn 7%T3 |
| What happens to T4(thyroxine) in the tissues | half is converted to T3 |
| This is 4x as potent as thyroxine | T3 |
| The thyroid gland is composed of large numbers of closed | follicules |
| follicules are filled with a secretory substance ______, and are lined by what cell types | colliod, cuboidal epithelial cells |
| what cell types lining follicules secrete into colloid | cuboidal epithelial cells |
| what is the major constituent of the colloid | thyroglobulin |
| Dietary substance required for formation of Thyroxine | Iodine |
| how much iodine required for TH each year, or per week | 50mg/year, or 1mg/wk |
| what happens to injested iodides once in the GI tract | absorbed into blood |
| What happens once Iodide in blood | most excreted (kid), 1/5 are actively removed from blood by thyroid and used for formation of TH |
| what is the term for the thyroid glands ability to remove I from blood | Iodide trapping ( 1st stg in TH formation) |
| iodide pump conc iodide. normal and max | 30x, 250x |
| The most important factor that influences the rate of iodide trapping | TSH |
| What synthesizes and secretes thyroglobulin into follicules | ER, and Golgi |
| Each thyroglobulin contains how many tyrosines | 70 |
| what is the substrate for iodine in TH formation | tyrosines on thryoglobulin |
| the thyroid hormones form _____ the thyroglobulin molecule | within, I + tyr = TH |
| The thyroid is unusual b/c it can | store large amounts of hormones |
| thyroid hormone can be stored for _______. thus the physiological effects of failed TH synthesis are | 2-3 months, not seen for months |
| Thyroglobulin is released into circulating blood T/F | F, T4 and T3 are cleaved from it |
| The main TH hormone used by tissues is | T3 ( conversion) 35ug/day |
| What percent of TH bind to P.proteins when entering blood | 99% |
| What is the major binding protein, minor | thryoxine-binding protein, Thryoxine-prealbumin and abumin |
| majority of TH secreted is_____ and binds to ____ | Thyroxine (T4), thyroxine binding-protein |
| At target tissue, T4 and T3 are released fast T/F | F, slowly b/c of high affinity to p. proteins |
| which hormone binds tighter | T4 (thyroxine |
| what is the half life of T4 | 6days, |
| What is the half life of T3 | 1 day |
| Generally the TH onset is ____ and the duration of action is ____ | slow, long |
| T4, latent period and duration of action | 2-3 days, max 10-12 days |
| after the 10-12 day max what happens | effects decrease with half life of 15 days |
| actions of T3 are how compared to T4 | 4x faster LP=6-12hrs and max 2-3 days |
Created by:
treater