Flashcards in thyroid physiology Deck (24):
what do the parafollicular C cells secrete?
where is thyroglubulin stored?
explain the steps in the synthesis of the thyroid hormones?
1. iodine taken up by follicular cells
2. iodine attaches to tyrosine residues on thyroglobulin to form MIT and DIT (building blocks)
3. coupling of the building blocks
4. stored in colloid until required
which thyroid hormone is most biologically active?
which thyroid hormone is more potent?
in what form are the thyroid hormones biologically active?
what to T3 and T4 bind to?
what molecule to most thyroid hormones bind to?
thyroid binding globulin (TBG)
when might there be increased thyroid binding globulin?
new born state
what will happen to the total T4 when there is increased TBG?
increased total T4 but not free T4
what will happen to total T4 when there is decreased TBG?
decrease total T4 but not free T4
when might there be decreased TBG?
chronic liver disease
roles of thyroid hormones?
increase basal metabolic rate
carb metabolism- increase blood glucose
lipid metabolism- increase lipolysis
protein metabolism- increase synthesis
development of foetal and neonatal brain
normal central nervous activity
how do thyroid hormones increase responsiveness to adrealine and noradrenaline?
by increasing number of receptors
affect of thyroid hormones on heart?
increase heart rate and stroke volume
what stimulates the release of thyroid hormones?
TSH from anterior pituitary
what stimulates the release of TSH?
TRH- thyrotrophin releasing hormone from hypothalamus
what does stress do to the release of TRH and TSH?
when are thyroid hormone levels highest?
what can cause a goitre?
symptoms of hypothyroidism?
slow pulse rate