it is about a zoology topic thyroid hormones

1. PRESENTED BY: VILLAYAT ALI
M.Sc 2nd Semester
Roll No: 03

2. CONTENT
 THYROID HORMONES
THYROID HORMONES SYNTESIS AND SECRETION
SYNTHESIS OF IODIDE INTO IODINE
FORMATION POF TYROSINE AMINO ACID FROM THYROGLOBULIN
TRANSPORT OF THYROID HORMONES

3. THYROID GLAND:
 Thyroid gland are located at the front part of trachea of neck region, which is
responsible for the formation of thyroid hormones
Thyroid gland is controlled by hypothalamus which release TRH which again
stimulate pituitary gland for the releasing of TSH.
When TSH is coming contact with thyroid gland then there is the stimulation of
follicular cell and releasing thyroid hormones
Thyroid gland contain follicles which cells which is made by follicular cell
Between the follicular cell there is colloid region or lumen which is responsible
for the formation of TH.
Thyroid hormone are made up of tyrosine amino acid which is an aromatic
compound and also contain Iodine.

5. THYROID HORMONE SYNTHESIS AND SECRETION
Thyroid hormones are synthesized in follicle cell and colloid region.
Thyroid hormone made by both iodine as well as tyrosine amino acid.
Synthesis of Iodide into Iodine:
 Iodine is present in our diet which reached into blood vessels in the form of
Iodide(presence of e − ).
 The iodide is then released into intersititial fluid(between the blood vessel and
follicular cell)
 Less no. of iodide outside the cell and more iodide inside the cell therefore
diffusion is not possible (active transport help in transport of iodide)
 Trapping of Iodide by mean of transporter (symporter) called as NIS( Sodium
Iodide Transporter) present at the wall of follicle cell.

6. Infkux of Na and iodide inside the cell
Again there is a Sodium/potassium channel are present, because there is no role
of Na in the cell therefore the Na is effluxed and K is influxed
Concentration of Iodide is now more in the cell therfore diffusion is more easy.
Iodide move into colloid region by mean of a transporter called Pendrin which is
a co transporter and hence the Iodide move into lumen and chloride are move
into the follicle cell.
Oxidization of iodide take place in the lumen by enzyme thyroid peroxidase and
convert it into Iodine (removal of electron from iodide).

7. Formation of tyrosine aminoacid from thyroglobulin:
In the follicular cell the ER make a protein called thyroglobulin (glycoprotein)
which is composed of almost 70 sequence of tyrosine aa.
Thyroglobulin is now transported into Golgi bodies which form a vesicle and
exocytosis take place.
Here we need to attachment of Iodine with tyrosine aa. With the help of enzyme
thyroid peroxidase.
Organification of iodine
MIT, DIT, T3, T4.
T3 = MIT + DIT (Thyroid peroxidase)
T4 = DIT + DIT (Thyroid peroxidase)

8.  The hormone is still attached to thyroglobulin chain.
 T3 and T4 again turn back into cell by the process of Endocytosis.
 Degradation of protein take place, when it in contact with lysosomal enzymes or
lysozyme and hormones became free.
 Secretion of hormones into the blood where a hormone carrier are present as named
TBG (thyroxine binding globulin)
 The amount of T4 in blood is high as compare to T3
 But when it reaches up to its target tissue the T4 the T4 further converted into T3 by
mean of another enzyme Deiodinase ( removal of iodine)

10. TRANSPORT OF THYROID HORMONES