thyroid gland Flashcards
what does thyroid gland tissue secrete
thyroxine (T4)
Tri-iodothronine (T3)
calcitonin
what arteries supply the thyroid with blood
superior and inferior thyroid arteries
which veins drain the arteries
superior and middle thyroid vein
inferior thyroid vein
what is the negative feedback loop in the thyroid gland
when T4 and T3 are released into peripheral tissues, they can loop back to the pituitary gland and the hypothalamus to switch the loop off
what are the 6 steps of thyroid hormone synthesis
- thyroglobulin synthesis
- uptake and concentration of iodide
- oxidation of iodide to iodine
- iodination of thyroglobulin
- formation of MIT and DIT
- secretion
what do you get when there’s and MIT and DIT coupled together
triiodothyronine
what do you get when there’s two DIT’s coupled together
thyroxine
where is triiodothyronine and thyroxine stored until requires
in colloid thyroglobulin
what is T4 converted to and what by?
converted to T3 by liver and kidney
which is the major biologically active thyroid hormone
T3
how is thyroid hormone transported
bound to serum proteins
what hormones are available to tissues
free/unbound ones
what are T3 and T4 bound by
plasma proteins
effects of thyroid hormone
- increased metabolic rate
- increased glucose uptake
- increased glycogenolysis and gluconeogensis
- decreased glycogenesis
- increased lipolysis
- decreased lipogenesis
- increased breathing rate
- increased HR and force of contraction
what does thyroid hormones do to basal metabolic rate
increases it
how do thyroid hormones increase basal rate
- increase number and size of mitochondria
- increase oxygen use and rates of ATP hydrolysis
- increase synthesis of resp chain enzymes
what do thyroid hormones do to thermogenesis
increase it
what do thyroid hormones do to carbohydrate metabolism
- increase blood glucose
- increase insulin dependent glucose uptake into cells
thyroid hormone effects on lipid metabolism
- mobilise fats from adipose tissue
- increase fatty acid oxidation in tissues
thyroid hormone effect on protein synthesis
increase it
how do thyroid hormones have an effect on growth
- growth hormone releasing hormone production and secretion requires thyroid hormones
- glucocorticoid-induced GHRH release is dependent on thyroid hormones
hypothyroidism affect on CNS
slow intellectual functions
hyperthyroidism affects on CNS
- nervousness
- hyperkinesis
- emotional lability
what is thyroid hormones permissive sympathomimetic action
thyroid hormones increase responsiveness to adrenaline and sympathetic NS neurotransmitter, noradrenaline by increasing number of receptors
where is D1 found
liver and kidney
where is D2
heart and skeletal, CNS, fat, thyroid and pituitary
where is D3
fetal tissue and placenta and brain
