Thyroid Gland Flashcards
what hormone is T3?
triiodothyronine
what hormone is t4?
thyroxine
what do c cells secrete?
calcitonin
what is the colloid?
sticky glycoprotein matrix
what do follicular cells manufacture?
enzymes that make thyroid hormones and thyroglobulin
what do follicular cells concentrate and transport to the colloid?
iodine
what catalyses the fusion of tyrosine and iodine?
thyroid peroxidase on apical membrane of follicular cells
what inhibits iodine transport into the thyroid gland?
thiocyanates: compound formed from detoxification of cyanides
tyrosine + 1 iodine =?
monoiodotyrosine
monoiodotyrosine + iodine = ?
diodotyrosine
monoiodotyrosine + diiodotyrosine = ?
triodothyronine
diiodotyrosine + diiodotyrosine = ?
tetrarodothyronine: THYROXINE
what is the transporter that transports iodine into the colloid?
pendrin
what do t3 and t4 bind to in the plasma?
thyroxine binding globulin
why thyroid hormone has a longer half life?
T4 as thyroxine binding globulin has a higher affinity for it
which thyroid hormone is more physiologically active?
T3 as the receptor has a higher affinity for it
what inhibits T4 changing to T3?
glucocorticoids
what inhibits thyroid stimulating hormone being released by the pituitary?
> negative feedback of thyroid hormones
glucocorticoids
somatostatins
what are the actions of thyroid hormones?
> raises metabolic rate, promoting thermogenesis
increases lipolysis
required for foetal brain development
increases proteolysis
critical for growth, stimulating GH receptor expression
what are the effects of hyperthyroidism?
> increased metabolic rate
altered nervous system function
elevated cardiovascular function
increased protein catabolism
what are the effects of hypothyroidism?
> decreased metabolic rate
distributed protein synthesis
altered nervous system function
reduced CVS function
what can cause goitre?
> increased trophic action of TSH on follicular cells
> over activity due to autoimmune disease
