Thryoid and GI hormone Test #4 Smith Flashcards
What is the largest gland in the body?
-Thyroid gland
T/F
The thyroid gland is extremely well vascularized
True
Do you have an active or inactive thyroid gland if you have colloid (thyroglobulin) abundant, large follicles, and cells lining the follicle are flat?
Inactive
Do you have an active or inactive thyroid gland if you have small follicles, cells lining the follicle are cuboid, and edges are scalloped with many small resorption gaps resulting from the uptake of colloid?
Active
What are the two primary functions of the thyroid?
- Secretion of two biologically active hormones by follicular cells
- Secretion by parafollicular cells
What do parafollicular cells secrete?
-Calcitonin
What is another name for parafollicular cells?
-C-cells
What do follicular cells secrete?
- Thyroxine (T4)
- Triiodothyronine (T3)
When does parafollicular cells release calcitonin?
-In response to high blood calcium levels
What does calcitonin do?
-Lower blood Ca2+ levels by inhibiting the resorbition of bone by osteoclasts
What hormone is formed from vitamin D
1,25-Dihydroxycholecalciferol
Where is vitamin D processed?
- Liver
- Kidneys
What secretes parathyroid hormone?
-Chief cells in the parathyroid gland
What causes Parathyroid (PTH) hormone to be secreted by Chief cells?
-Low blood Ca2+
What does 1,25-Dihyroxycholecalciferol do to Ca2+?
- Increases absorption from the intestine
- Increases stores in bone
How does PTH mobilize Ca2+?
-Stimulate osteoclasts
What are the thyroid hormones synthesized from?
- Iodine
- Tyrosine
What thyroid hormone is produced exclusively by the thyroid gland?
-T4
What thyroid hormone is produced extrahyroidally from its precursor?
-T3
What is the precursor for T3?
-T4
What is the vast majority of thyroid hormone produced by the thyroid?
-T4
What happens to most T4 that is produced?
-Gets converted to T3
T/F
T3 is 4x more potent than T4
True
Where is most of T3 made?
Liver
What is the inactive form of T3?
rT3
What does the hypothalamus stimulate the anterior pituitary to produce?
-TSH (thyroid stimulating hormone or thyrotropin)
What does thyrotropin/TSH do?
-Stimulate thyroid gland to produce T4
If you have low T4, low T3 or cold exposure what occurs?
-Increase T4 and T3 production
T/F
Increasing T4 and T3 is calorgenic
True
Feedback inhibition at what level most efficiently inhibits TRH secretion?
-Anterior pituitary
What enzyme is responsible for making T3 from T4?
-Deiodinase enzymes
T/F
T3 can act independently of HPT axis regulation in peripheral tissues
True
What do thyroid hormones target?
- Nuclear receptors
- Modulating gene expressions
If you are under stress and or fasting the body converts ___ T4 to T3 and ____ T4 to rT3
Less
More
T/F
Without sufficient iodine thyroid hormones are not released and TSH builds up
True
The amount of T4 produced and released by the thyroid gland is controlled directly by TSH released by the _____?
Anterior pituitary
What is the best known stimuli for increasing the rate of TSH secretion by the anterior pituitary?
-Exposure to Cold
What protein are stores of T3 and T4 found?
-Thryoglobulin (TGB)
What Thyroid hormone has 4 iodine molecules attached?
-T4
T/F
5’ deiodination of T4 results in rT3 which is inactive
False
5’ deiodination does T4 to T3
5 deiodination does T4 to rT3
What is essential to normal thyroid function
-Iodine
What are the only cells in the body that can absorb iodine?
-Thyroid
What can cause a Goiter?
-Too much TSH or HCG
What do patients with IDD most commonly present with?
-Goiter
What is the most extreme manifestation of severe IDD?
-Cretinism
What disease is linked to hypothyroidism?
-Hashimoto’s disease
What disease is linked to hyperthyroidism?
-Graves disease
What hormone can act in an endocrine, paracrine, and neurocrine fashion in digestion?
-CCK
What is the source of gastrin?
-G cells in stomache
What stimulates the release of gastrin?
-Stimuli from consumption and peptides in gastric lumen
What is the action of gastrin?
-Stimulate gastric acid secretion
What is the source of CCK?
-I cells from duodenum and jejunum
What is the stimuli for release of CCK?
-Digestive products of fats, fatty acids, and monoglycerides
What is the action of CCK?
-Contract gall bladder expelling bile into small intestine
What is the source of secretin?
-S cells in duodenum
What is the stimuli for release of secretin?
-Acidic pH in lumen of Small intestine
What is the action of secretin?
-Stimulate pancreas to release bicarbonate
What is the source of Gastric inhibitory peptide?
-Mucosa of upper small intestine
What is the stimuli for release of Gastric inhibitory peptide?
- Fatty acids
- Amino Acids
- Carbohydrates
What is the action of gastric inhibitory peptide?
-Inhibit gastric secretion and increase insulin release
What are three major pancreatic hormones?
- Glucagon
- Insulin
- Somatostatin