Lecture 6- Thyroid Gland Flashcards
What are the functional units of the thyroid gland called?
Follicles
What cells are dispersed between the follicles?
C cells (parafollicular cells)
What do c cells secrete?
Calcitonin
What do the central cavities of the follicles contain?
Colloid
What is the major constituent of colloid?
Thyroglobulin
What hormone are follicular cells dependent on?
Thyroid stimulating hormone
What 2 molecules are required for thyroid hormone synthesis?
Iodine and tyrosine
Which cells produce thyroglobulin?
Follicular cells
How is thyroglobulin moved into the follicle lumen?
Exocytosis
Where do follicular cells take up iodide from?
The blood
Where does oxidation of iodide to molecular iodine?
Follicular cells
Where does iodine attach to thyroglobulin?
Tyrosine residues
Where does iodine-tyrosine attachment take place?
Colloid
What 2 molecules are formed from iodine-tyrosine attachment?
Monoiodotyrosine and diiodotyrosine
What 2 molecules are formed from coupling of monoiodotyrosine and diiodotyrosine?
T3 and T4
How does secretion of T3 and T4 to the follicular cell occur?
Endocytosis
Once T3 and T4 enter the follicular cells, what do they fuse with?
Lysosome
How do T3 and T4 enter the bloodstream from the follicular cells?
Diffusion
Which hormone, T3 or T4 is secreted in greater proportions?
T4
Which molecule, T3 or T4, is more potent?
T3
Which 2 organs convert T4 into T3?
Liver and kidneys
What regulatory effect do thyroid hormones have?
Negative feedback to both anterior pituitary and hypothalamus, inhibiting thyroid stimulating hormone and thyrotropin releasing hormone release
What kind of receptors are thyroid stimulating hormone receptors?
G protein coupled receptors
What hormone do thyroid hormones stimulate the release of?
Human growth hormone
What are the effects of thyroid hormones on metabolism?
Increased metabolic activities
What is the effect of thyroid hormones on oxygen consumption?
Oxygen consumption increases to most metabolically active tissues
What is the effect of thyroid hormones on basal metabolic rate?
Increased by up to 60-100%
What is the effect of thyroid hormones on body temperature?
Heat is released during metabolic reactions, increasing body heat
What are the effects of thyroid hormones on catecholamine receptors?
Increased production of receptors so cells are more responsive (upregulation)
What are the cardiovascular effects of thyroid hormones?
Increased heart rate, force of contractions and cardiac output
