2. Follicular cells are bipolar cells - with an apical side that surrounds a
central cavity or lumen filled with the colloid, which is a fluid that
contains the precursor hormone thyroglobulin.
4. The basolateral membrane
contains a sodium-iodide
symporter, which pumps two
sodiumions into the cell down
their electrochemical gradient, in
order to bring one iodide ion into
the cell fromblood.
Tyrosine iodised
•to monoiodotyrosineandthen
•to diiodotyrosine.
When two diiodotyrosinesare coupled,
•thyroxine(tetraiodothyronine)is formed,
pinocytosisof iodised thyroglobulin
5. Thyroid gland cells produce
• thyroxine ( 𝑇4)
• T4 is created in greater amounts than T3.
• 90% of the metabolically active hormones
• Almost all thyroxine in the tissues is
converted to triiodothyronine 𝑇3
• difference in the degree and the onset of
the effect.
• a longer half life of six to eight days
• triiodothyronine ( 𝑇3)
• only 9%
• (1 % inactive reversed triiodothyronine 𝑟𝑇3)
• about 4 times more effective than thyroxine
• a half life of one to two days
7. thyroxine binding globulin or TBG, but they also bind to
albumin and transthyretin
Bound T3 and T4 acts like a reservoir of hormone that’snot biologicallyactive. In fact, only a
small amount of T3 and T4 will travel unboundin the blood - about 0.03% of T4 and 0.3% of
T3
8.
9. • T3, T4 effect
• stimulates the oxgen consumption
• impacts the body growth and
development
• regulates metabolism
10. • increasing the metabolic rate in almost all body tissues, what
increases the O2 consumption.
• the increase of
• the number and the activity of mitochondria,
• activation of ions transport through the cell
membrane
• activate $ce{Na+}$-$ce{K+}$-ATP-ase
• activation of metabolism of fatty acids they mobilise.
11. • T3, T4 effect
• increase the $ce{02}$ release from
haemoglobin.
• stimulate the heat production instead of
forming ATP
• this effect is called calorigenic action
12. • T3, T4 effect
• influence the carbohydrate,fat and
protein metabolism
• Increase
• glucose absorptionfrom the
intestinal tract
• enhance
• glycolysis, gluconeogenesis
• lipolysis and fatty acids production
13. • T3, T4 effect
• anabolic effect
• enhancing their synthesis
• Catabolic effect
• releasing proteins mainly from the
muscle
14. • T3, T4 effect
• Increased metabolic rate by
• increased oxygen consumption
• increased minute ventilation
• increase the erythropoietin secretion
• to elevate the capacity for oxygen
transport in the blood
15. • T3, T4 effect Permissiveness
• Increasing the number of beta-
adrenergic receptors
• increasing epinephrine's effect on
that cell
• Without the thyroid hormone,
epinephrine would have only a weak
effect
16. • T3, T4 effect
• Increased effect of of growth hormone
and somatomedins
• regulate the bone growth and
epiphyseal closure
• ossification,
• fusion of epiphyseal plates
• bone maturation.
17. • T3, T4 effect
• on brain development during foetal and
early postnatal life
• regulate
• synaptogenesis,
• differentiation and migration of
neurons
• their mineralization.
18. Synthesis and release of thyroid hormones
• is regulated
through the hypothalamo-pituitary-
thyroid axis
• Hypothalamic neurons
• secrete thyrotropin-releasing hormone
• TRH
• increases the secretion of thyroid-
stimulating hormone
• from the anterior pituitary
