What is thyroid?
The thyroid is a hormone which is secreted form some specific a gland in the human.
When it secrete more is called hyperthyroidism and when it secretes less is called hypothyroidism. Before I explain about hyperthyroidism and hypothyroidism first explain how thyroid hormone secreted in our body.
How thyroid hormone secreted ?
Thyroid hormone is synthesized and store in follicularcells as form of thyroglobulin molecule.thyroid gland is present in neck of human body and it shape is like butterfly.
Follicular cells which is present in thyroid gland are play mazor roal for this synthesis .
Hypothalamus release the hormone name thyroid stimulating hormone (THS) to stimulating follicular cell to synthesized thyroglobulin which is common chain of tyrosin ring.
Follicular cells outer side is blood vessel .folicular cell outer membren contain the NA I+ symporter which is take iodide in side cell and inside of the membren ca+ symportor which is pass the iodide to lumen of the follicular cell , then iodide oxidase and to form the iodine .this iodine binds with the thyroglobulin of tyrosin ring to produce MIT and DIT.
MIT –is known as when one iodine bind with tyrosine
DIT is known as when two iodine bind with tyrosine
It synthesis and utilization are done mainly 5 process
1. Iodide uptake
In our body collect the iodine 30-50 mg form food and water.form this amount 1/5 pertion is present in the thyroid .in our body thyroid cell have more active transporter which is collect the low concentration of iodine .iodide uptake by the NA+ I- symporter.
2. Oxidation and iodination
In this procress iodide which is present in side the follicular cell are goes apical membren by transporter PENDRIN or simple ca+ aion transporter.
After this procress Iodination is occour and it produce iodide to iodine which is able to bind with the tyrosil of the thyroglobulin with out any help of enzyme.
And form monoiodotyrosine (MIT) and diiodotyrosine (DIT)
In this procress one MIT and one DIT are produce T3 , two DIT are coupling produce T4. In this procress if more more MIT is present then T3 are produce more .cupling is oxidative reaction it is catalyzed by thyroid peroxidase
4. Storage and release
Thyroglobulin are store the T3 and T4 ,then is again pass to interior of the follicles and remain stored in to thyroid colloid till required .when it required taken back to cell by procres endocytosis and broken down the lysosomal protease.T3 and T4 are release to blood circulation.MIT and DIT are store for reutilization.in our body 60-90 miro gram of T4 and 10-30 micro gram of T3 produced.
5. Peripheral conversion of T4 to T3
Mainly T4 is converted to T3 in theliver and kidney. In this conversion Equal amount of iodine is bind with tyrosin .But in some place T4 is directly act on the brain and pituitary.
|Thyroid gland internal stucture|
Thyroid hormone Metabolism
This hormone is easily bound with plasma protein.Arround 90-95% of T4 is bound with plasma and rest of all are T3.
In the order of affinity for T4 are
1 Thyroxine binding globulin
2 Thyroxine binding prealbumin
Plasma t1/2 of T4 is 6-7 days, and plasma t1/2 of T3 1-2 days.
This hormone are helps normal growth and development. Best example is metamorphosis of tadpole to forg.
Deficiency of T3 and T4 are main importance of growth and development delay .it directly affect the growth of organ and tissue.it also affect nervous system growth.
T3 and T4 are metabolized lipid by the enhance the lipolysis that the region of cholesterol level decreases.In the blood LDL level are also decrease.
T3 and T4 have metabolized the carbohydrate by enhancing the process glycogenolysis and gluconeogenesis in the liver as a result glucose absorption is increased.
T3 and T4 are the synthesis of certain proteins is increased. but in some cases it causes T3 ia act as catabolic reaction .that the reason weight loss in hyperthyroidism.
Hypothyroidism is occour due to less secretion of thyroid hormone form thyroid gland .so that there are many diseases are shown like
Papillary carcinoma of thyroid
Empirical use of Refractory anaemias , menstrual disorders, infertility tritment, chronic healing of ulcers, obstinate constipation
Hyperthyroidism is occour due to excess secretion of thyroid hormone form thyroid gland .due to hyperthyroidism symptom are shown most common result are Graves’s disease, and toxic multinodular goiter,asolitary thyroid adenoma, and inflammation.