Term
| Which is more potent, T4 or T3? |
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Definition
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Term
| What type of receptor does TSH use? |
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Definition
cAMP G-protein (Gs)
IP3 G-protein (Gq) |
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Term
| What type of receptor does TRH used? |
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Definition
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Term
| How is secretion of thyroid hormones controlled? |
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Definition
| T4 has negative feedback effects on TSH-producing cells in the ant pit, and paraventricular nucleus of the hypothalamus. |
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Term
| What stimulates TRH production & release? |
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Definition
| alpha-1 adrenergic nerves stimulate production of prePRO hormone, pulsatile release of TRH from the median eminance |
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Term
| What do parafollicular cells do? |
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Definition
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Term
| How are thyroid hormones produced? |
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Definition
1. Na/I symporter brings iodide into thyrocytes (follicular cells)
2. Thyroglobulin is produced and exits into the lumen of follicles
3. Tg organification (iodination) via thyroid peroxidase
4.MIT & DIT residues condense to form T3 & T4.
5.Thyroglobulin moves from lumen into thyrocyte via endocytosis
6. Lysozomes cleave T3/T4 and are released. |
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Term
| What enzyme carries out thyroglobulin organification? |
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Definition
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Term
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Definition
| When cleavage results in iodine binding in 5' instead of 3'. Results in impotent version of T3 |
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Term
| Which is produced in greater quantities, T3 or T4? |
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Definition
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Term
| What is the Wolff-Chaikoff effect? |
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Definition
| dietary excess of iodide will prevent iodide trapping (active uptake of iodide) by follicular cells |
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Term
| How are thyroid hormones transported? |
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Definition
bound to thyroxin-binding globulin (inactive)
a small percentage are free, and these ones are biologically active! |
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Term
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Definition
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Term
| Triiodothyronine is (T3/T4) |
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Definition
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Term
| How is T3 delivered to its target cell? |
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Definition
1. Transport protein/T3 complex reach cell, T3 enters cell and travels into nucleus.
2. T3 binds to R1 receptor, which is attached to HRE
3. HRE activates gene expression.
ALTERNATE STEP 2
-isoforms of R1 receptor dimerize
-RxR receptor binding activates gene expression |
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Term
| What is HRE, and what is it's importance? |
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Definition
Hormone Response Elemant
-R1 and RxR receptors are attached to HRE in the nucleus
-when T3 binds to R1, it 'turns on' gene expression |
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Term
| Which has a longer half-life, T3 or T4? |
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Definition
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Term
| What is thyroid hormone conjugation? Where does it occur? |
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Definition
| breakdown of T3/T4 in LIVER, products then excreted via bile & kidneys |
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Term
True or False
Thyroid hormones are essential for growth in brain mass, dendrite formation & synapsis formation |
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Definition
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Term
| Primary thyroid disease indicates an issue with... |
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Definition
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Term
| Secondary thyroid disease indicates an isssue with... |
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Definition
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Term
| What causes goiter associated with hypothyroidism? |
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Definition
| low iodide intake/uptake, means the body can't produce as much T3/T4. Hypothalamus will increase TRH production, ant pit will increase TSH production, but no response from the thyroid. Gland will enlarge to try and compensate |
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Term
| What causes goiter associated with hyperthyroidism? |
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Definition
Graves disease
-body produces antibodies which target the thyroid, causing it to swell and produce lots of hormone
-TRH will be low & TSH will be low bc body says "whoa too much!" |
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Term
| What is euthyroid sick syndrome? |
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Definition
| Reverse T3 is produced, low amounts of T3/T4 produced. Also, T4 is converted to rT3. |
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Term
True or False
Euthyroid sick syndrome can be treated with T4 |
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Definition
false
T4 gets converted to rT3, won't be beneficial |
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