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26 Cards in this Set
- Front
- Back
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mode of action of thyroid -> hypopit feedback
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downregulates the number of receptors
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thyroid histology
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big colloid nodules (kind of looks like fat); that's where thyroid globulins are; follicle = simple cuboidal epithelium surrounding colloid nodule
normally the whole internal space of follicle is filled with colloid (thyroglobulin) |
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C cell
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calcitonin secreting cell (parafollicular cell); its around the follicle (parafollicular); usually found at the junction between 2 or 3 nodules
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parathyroid gland
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separated from the capsule of the thyroid gland by their ownc onnective tissue capsules; produces PTH (leads to low serum calcium)
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follicular epithelium
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simple cuboidal; surrounds colloid
apicle surface faces colloid |
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where does the ring in thyroid hormones come from?
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tyrosinne molecules; combine two tyrosine molecules; add iodines to them
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thyroid gland functiosn
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regulates basal metabolic rate
improves cardiac contracility, increases effect of all other hormones, increases bowel motility, increases speed of skeletal muscle, decreases cholesterol (LDL), required for proper fetal neural growth thyroid gland will affect all other hormone levels |
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young female trying to get pregnant but can't
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check the thyroid; could be related to endocrine axis but she could also just be hypo/hyperthyroid
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LDL
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out in blood, taken up in liver and processed
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where is thyrodglobulin synthesized
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thyroid epithelial eclls and secreted into the lumen of the follicle
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how do we get iodine and tyrosine into the body
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iodine and tyrosine obtained from the diet and absorbed into the blood and absorbed by the thyroid fgland
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leading cause of preventable mental deficiencies
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hypothyroid
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where does tyrosine go in thyroid
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into cell as an amino acid
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where does iodine go in thyroid
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into colloid
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thyroid hormone
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aromatic amino acid derived hormone;
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half life of T4/3
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T4 half life is 7 days vs T3 .75 day; provides a criculating pool
Most T4 is released by the gland itself; |
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major source of T3
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T4 in the blood (80% of T3 comes from circulating T4)
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how to get rid of T3/T4 from the blood
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free T3/4 is entering cells; it then elicits actions and gets destroyed; mainr eason for the destruction of 3 and 4 is its normal action
when 3/4 is pulled into cell to act on nucleus it is not re-released; binding proteins regulate this whole process |
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conversion of T4 to T3
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deiodinases
different types found in different tissues point: T4 -> T3 in order for it to be used |
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source of calcitonin
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Parafollicular C cells of the thyroid
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calcitonin synthesis
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synthesized a prohormone called procalcitonin; cleaved to produce calcitonin + CCP in C cells (in neural tissues it can be cut different into CGRP, can't get calcitonin and CGRP from same gene bc have overlaping parts, but abnormally functioning C cells can produce CGRP; can also get VIP)
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major action of calcitonin
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inhibit osteoclasts and osteocytic osteolysis activity and reduce bone degradatino (decrease bone resorption of calcium = lower serum calcium levels)
not important in normal calcium homeostasis (but in pts w pagets, or other mineralization dz calcitonin can play more of a role) |
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why cant calcitonin tx osteoperosis
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very minimal effect; too short acting/body downregualtes R
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why is calcitonin important if it has such minimal effect
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its a good tumor marker for medullary carcinoma of the thyroid
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marker for medullary carcinoma of the thyroid
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calcitonin
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site of metastasis of medullary carcinoma of the thyroid
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goes to bone, liver, lungs and brain
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