Renal & Endo Flashcards
function of feedback loops
maintain homeostasis
what connects 2 lobe of thyroid gland
isthmus
function of thyroid
Hormone that regulates cellular metabolism, growth, body system functions, & regulation of Calcium Levels
what does the thyroid store
thyroid hormone (sequesters circulation Iodine)
thyroidal secretion is mostly ____________
the prohormone T4
T3:T4 Ratio of secretion
1:10
80% of T3 deiodination of T4 by body tissues
elimination time of T3 and T4
T4 (7 days)
T3 (24-30 hours)
which is more potent: T3 or T4
T3 is 3-4 times more potent than T4
T3 and T4 protein binding
T3 & T4 are mostly protein bound.
Free & biologically active = T3 (0.3% of total T3)
Free & biologically active = T4 (0.03% of total T4)
functions of T3 and T4
- Promote gene transcription & basal cell metabolism.
- Intestinal absorption of glucose & insulin transport of glucose into cells.
- Enhance hepatic gluconeogenesis & glycogenolysis
- Increase Lipid utilization from adipose tissue
- Increases β-adrenergic receptors & sensitivity to catecholamines ➔ increases myocardial contractility, decreases SVR, and increases systemic volume.
- Promote in-utero brain development.
- Thermogenesis
- heat from body’s vital processes
- adaptive thermogenesis
thyroid function is regulated by… (3)
TSH
TRH
T3, T4 & circulating levels of Iodine
where is TSH produced
anterior pituitary gland
function of TSH (2)
- enhances/regulates iodine uptake
- T3/T4 production/secretion by thyroid gland
TRH location of production and function
produced in hypothalamus & promotes TSH secretion
High (or low) T3/T4 levels in the hypothalamus/anterior pituitary gland regulate ____________
secretion of TRH & TSH.
what do high iodine levels do to T3/T4 production
down-regulate T3/T4 production
how are T3/T4 produced?
Thyroid hormone is produced and activated by____________
Iodine in the Thyroid Gland
Dietary intake of Iodine is ____________
reduced to Iodide in the GI tract ➔ Iodide is absorbed by the thyroid gland
Iodide bounds with ____________ ➔ forms ____________ ➔ ____________ & ____________ couple with____________ to form T3 & T4
Iodide bounds with Tyrosine ➔ forms Iodotyrosine ➔ Monoidotyrosine & Diiodotyrosine couple with thyroperoxalase to form T3 & T4
T3 & T4 attach to ____________ and are stored in the gland as ____________
thyroglobulin and are stored in the gland as a colloid
T3 & T4 are released into circulation after ____________
proteolysis from colloid thyroglobulin
function on parathyroid glands
Secrete calcitonin in response to high Ca++ levels, which decrease levels of calcium & phosphorus
calcitonin inhibits: (2)
- Osteoclast activity
- Renal reabsorption of calcium and phosphorus