Thyroid Gland Flashcards
This gland releases which hormone?
Thyroid hormone. T3 & T4
T3 is also known as?
Triiodothyronine. 3 atoms of iodine
T4 is also known as?
thyroxine or tetraiodothyronine. 4 atoms of iodine.
What do T3 & T4 do?
increase metabolism & increase delivery of oxygen to support metabolism
When TH levels increase what kind of feedback inhibits the release of ___ & ___?
negative feedback; TSH, TRH
Although T3 & T4 get secreted, it is mostly which that gets secreted?
T4
Thyroid hormones, just like steroid hormones, are…
lypophilic
What is the structure of the thyroid gland?
two large lobes connected by broad isthmus. follicles on outside of gland, follicles filled with colloid. colloid filled with thyroglobulin.
What are the other hormone-secreting cells on the outside of the thyroid gland referred to as?
extrafollicular cells (C cells)
How is T3 & T4 produced?
food –> absorbed by intestine –> blood carries as iodide to thyroid gland –> iodide pump moved them into follicular cells _> oxidized to put in reactive form -> thyroglobulin released into lumen -> enzyme on cell surface adds iodine to it
When one iodine is added?
MIT (monoiodotyrosine)
When 2 iodines added?
DIT (diodotyrosine)
T3 when broken down is just ..
MIT + DIT
T4 when broken down is just..
DIT + DIT
When the thyroid cells get TSH, they do what to thyroglobulin?
absorb it by pinocytosis
How does TH get to target cells?
lysosomal enzyme hydrolyzes peptide chain of thyroglobulin which frees TH. TH goes into blood & binds w/ transport protein so it can get to target cells.
Oxytocin is unusual in that it has a ___ feedback loop
positive
Growth hormone, unlike other pituitary hormones, has a ___ effect
widespread
What does growth hormone do?
stimulates bone, cartilage, muscle, fat, liver. causes liver to secrete IGF-1 & IGF-2
IGF-1 & IGF-2 are known as? They do what?
somatomedins. mediate effects of growth hormone
what is an effect of IGF?
prolongs behavior of GH, half life only 6-20 mins
what does IGF-1 do?
accelerates bone growth in response to GH, epiphyseal plates, osteogenic/chondrocytes stimulated.
GH & IGF turn on what?
protein synthesis
GH plays a role in __ metabolism
lipid; stimulate adipocytes to catabolize fat. releases triglycerides into fatty acids & glycerol. protein sparing effect
GH shuts down ___ catabolism
protein
GH turns on ___ synthesis in liver
glucose
GH impacts ___ balance. how?
electrolyte; promotes retaining of them
GH promotes ___ retention
Ca; small kidney
GH also plays a role in ___ metabolism.
carbohydrate; glucose-sparing effect mobilizes fatty acids, cells don’t depend on glucose to make ATP
GH stimulates protein ___ so cartilage & bone can lay down more Ca & cartilage to support bone
protein
exercise secretes __
GH
hypoglycemia can trigger __
GH
high carb meals suppress ___ because?
GH; stimulates glucose production in liver
highest level of GH is when you __
sleep
