THYROID GLAND
It is the largest gland in the human body and has 2 lobes. It lies below the
larynx.
It weighs about 15 to 20 grams.
Thyroxine, T3, T4 are hormones secreted by this gland.
It secreted 93% active thyroxine, 7% tri-iodothyronine.
The blood flow of thyroid gland is about five times the weight of gland each
minute, which is as great as any other area of the body.
It is filled with proteinaceous material colloid which has thyroglobulin, which
contains thyroid hormone.
Thyroglobulin can store 30 thyroxine hormones at a time and in this form
thyroid hormones are stored in sufficient amount to be supplied upto 2 to 3
months(this prevents deficiency of hormones till depletion of stores).
Thyroid gland is composed of follicles.
“THYROID HORMONES”
In blood T3 & T4 are bound to plasma proteins (thyroxin binding globulin, pre-
albumin or albumin).
T4= 0.1% is free
T3= less than 1% is free.
Half Life= (T4=7 days) , (T3=1 day)
Free thyroid hormones are taken up by tissues.
“Elevated(pregnancy/raised estrogen) or reduced(liver/kidney disease) levels
of TBG doesn’t influence free hormone levels”.
T4 is produced in large amounts by thyroid gland but are deiodinated at 5 th
position and converted to T3 or RT3 because T3 has more affinity to the
receptors in the nucleus.
T4 is considered as prohormone for T3.
Thyroid hormones increases metabolic rate by increasing Na-K-ATPase activity,
oxygen consumption, heat production.
They promote growth and development of CNS and skeleton, teeth, epidermis
etc.
Iodine is essential for formation of thyroid hormones and it is ingested
through gut into the blood.
It is the largest gland in the human body and has 2 lobes. It lies below the
larynx.
It weighs about 15 to 20 grams.
Thyroxine, T3, T4 are hormones secreted by this gland.
It secreted 93% active thyroxine, 7% tri-iodothyronine.
The blood flow of thyroid gland is about five times the weight of gland each
minute, which is as great as any other area of the body.
It is filled with proteinaceous material colloid which has thyroglobulin, which
contains thyroid hormone.
Thyroglobulin can store 30 thyroxine hormones at a time and in this form
thyroid hormones are stored in sufficient amount to be supplied upto 2 to 3
months(this prevents deficiency of hormones till depletion of stores).
Thyroid gland is composed of follicles.
“THYROID HORMONES”
In blood T3 & T4 are bound to plasma proteins (thyroxin binding globulin, pre-
albumin or albumin).
T4= 0.1% is free
T3= less than 1% is free.
Half Life= (T4=7 days) , (T3=1 day)
Free thyroid hormones are taken up by tissues.
“Elevated(pregnancy/raised estrogen) or reduced(liver/kidney disease) levels
of TBG doesn’t influence free hormone levels”.
T4 is produced in large amounts by thyroid gland but are deiodinated at 5 th
position and converted to T3 or RT3 because T3 has more affinity to the
receptors in the nucleus.
T4 is considered as prohormone for T3.
Thyroid hormones increases metabolic rate by increasing Na-K-ATPase activity,
oxygen consumption, heat production.
They promote growth and development of CNS and skeleton, teeth, epidermis
etc.
Iodine is essential for formation of thyroid hormones and it is ingested
through gut into the blood.
