thyroid Flashcards
site of production of thyroid hormone?
follicles
where are the 4 parathyroid glands?
posterior part of gland
what cells produce there hormone and encircle the colloid in which the hormone passes into for storage line them ?
cuboidal epithelial cells
what are parafollicular cells?
found outside the follicles
what do parafollicular cells produce
calcitonin
production and releease of thyroid hormones is under the control of
hypothalamic pituitary axis
where is TRH released from ?
hypothalamus
TSH?
pituitary
what feedback does thyroid hormone exhibit on both TRH and TSH?
negative feedback
what does stress do to TRH?TSH?
decrese
what does cold do to TRH in children>
stimulates TRH release (to warm up)
when is release of TRH highest?
in the evening
90% of thyroid hormone produced is?
T4
10% of thyroid hormone produced is?
T3
which one is thyroxine?
T4
thyroid hormone is produced via uptake of _______ which is attached to _______ __________ of _________ to produce either T3 or T4?
iodine
tyrosine residues of thyroglobulin
upon release, what three binding globulins does T3 and T4 bind to?
thyroxine binding globulin
thyroxin binding pre albumin
albumin
what is the main binding globulin?
thyroid binding globulin
when are levels of TBG increased?
pregnancy
COCP
tamoxifen
hepatitis
decreased levels of TBG?
cushings
large dose of steroid
nephrotic syndrome
is bound t3/t4 active
no, only free
what is the most biologically active form of thyroid hormone?
T3
where does T4 undergo peripheral conversion to T3?
in the skin, kidneys and liver upon release into circulation
biological effects of T3?
increased thermogenesis
increased basal metabolic rate
increased carbohydrate and lipid breakdown, protein synthesis
causes growth
normal cognitive function
enhancement of response to sympathetic nervous system due to increased expression of receptors
