L26 - Thyroid function Flashcards
what is the function of the parathyroid
involved in blood Ca level regulation
name the thyroid hormones and what they’re derived from
T3
T4
tyrosine
what is colloid?
found within thyroid follicles and stores T3 & T4 (in thyroglobulin)
where are the thyroid hormones synthesised (T3 & T4)
in principle cells that line thyroid follicles
what cells are found between thyroid follicles and what are their function
C cells / parafollicular cells
secrete calcitonin - involved in regulation of Ca2+ levels
what is unique about the thyroid gland?
only gland that contains follicles
only gland that stores its secretory products in inactive form outside the cells
what happens to tyrosine to form T3 and T4
gets iodinated
what is T3 made from
2x tyrosine
3 x iodine
(1x di-iodotyrosine & 1 x monoiodotyrosine)
what is T4 made from
2x tyrosine
4x iodine
(2 x di-iodotyrosine)
which thyroid hormone is the most potent
T3
which thyroid hormone is the most abundant
T3
where is the target receptor that T3 and T4 act on?
in the cell nucleus of target tissues
what is the overall effect of thyroid hormones?
increase overall metabolism
increase basal rate
involved in body temp
what is the effect of the receptor after T3/T4 have bound
stimulate / inhibit gene expression
what is the effect of Thyroid hormones on muscles
- increase protein breakdown
- increase glycogenolysis
(increase [glucose])
what is the effect of Thyroid hormones on Red blood cells
increases formation of RBCs
what is the effect of Thyroid hormones on liver
- increases glycogenolysis (glycogen breakdown)
2. increases gluconeogenesis
what is the effect of Thyroid hormones in bones
involved in growth and maturation
what is the effect of Thyroid hormones on heart
- increase HR
- increase contractility
‘——> increase CO - increase blood pressure
what is the effect of Thyroid hormones on CNS
growth and development
explain HPT axis
- hypothalamus releases TRH to anterior pituitary
- ap releases TSH to thyroid gland
- TSH stimulates production of T3 & T4 by stimulating iodine uptake and colloid endocytosis
what are the general effects of hyperthyroidism (increased levels of thyroid hormones)
- increased basal metabollic rate
- increased cardiac activity
- weight loss - muscle wasting
- hypertension
- hyperglycaemia
what are the general effects of hypothyroidism (decreased levels of thyroid hormones)
- decreased basal metabollic rate
- decreased heart activity
- weight gain
- slow reflexes and mental processes (CNS)
what do T3 and T4 bind to in the blood stream
thyroid binding globulin (TBG)
