Endocrine: Thyroid/Parathyroid/Diabetes #4 Flashcards
a chemical substance produced by endocrine glands that control and regulate the activity of certain target cells or organs:
Hormones.
Many are made in one part of the body and control/reguylate the activity of certain cells or organs in another part of the body.
Thyroxine affects many body tissues when released directly into the circulation. What gland produces it?
Thyroid gland.
AKA T4.
Organs can act as endocrine glands by secreting hormones. How are kidney’s an example of this?
They secrete erythropoietin, a substance that stimulates RBC production.
The heart secrets ANP, the GI secretes numerous peptide hormones (gastrin, etc).
What is the major physiologic role of ADH?
Regulate fluid volume.
Synthesized in hypothalamus then secreted by posterior pituitary (stored there until stimuli triggers)
Causes renal tubules to reabsorb water, making the urine more concentrated.
A rise in plasma osmolality and/or hypovolemia stimulated release of ADH.
This is highly vascular. Its size is related to TSH secretion by the anterior pituitary:
Thyroid gland.
The 3 hormones produced are
- Thyroxine (T4)
- Triiodothyronine (T3)
- Calcitonin
This accounts for 90% of thyroid hormone produced:
T4
This thyroid hormone is much more potent and has greater metabolic effects:
T3
The thyroid gland secretes only about 20% of the circulating T3. The rest comes from the conversion of T4 after its release into the bloodstream.
What is necessary for the synthesis of T3 and T4?
Iodine.
Both hormones affect metabolic rate, caloric requirements, O2 consumption, carb and lipid metabolism, growth and development, brain function, and other NS activities.
What inhibits the secretion of both TRH from the hypothalamus and TSH from the anterior pituitary gland?
High circulating thyroid hormone levels inhibit their secretion.
left off on calcitonin
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