Thyroid Physiology Flashcards
which two cells make up the thyroid gland
follicular cells and parafollicular cells
what is the function of follicular cells
produce and store thyroid hormone
what is the function of parafollicular cells
produce calcitonin which lowers serum calcitonin levels
describe the hypothalamic-pituitary-thyroid axis
hypothalamus releases thyrotropin releasing hormone acting on anterior pituitary to release thyroid stimulating hormones which acts on thyroid to release T3 and T4, when levels are sufficient of T3,T4 negative feedback inhibits TSH production
where does thyroglobulin synthesis occur
in follicular cells
iodine binds which molecule to form thyroglobulin
tyrosine
how is T3 formed
MIT + DIT
how is T4 formed
DIT + DIT
which hormone is most abundant
T4
which hormone is most metabolically active
T3
where is T4 converted to T3
kidneys and liver
can thyroid hormones travel freely in the blood
no, bound to carrier proteins
list the carrier proteins that thyroid hormones are bound to in the blood
thyroxine binding globulin (TBG)
thyroxine binding pre-albumin
albumin
list factors that increase levels of TBG
pregnancy, COCP, tamoxifen, hepatitis
when are thyroid hormones biologically active? freely or bound to carrier proteins
when free
