Thyroid Hormones
6-Nov-21 Thyroid Hormones 1
INTRODUCTION:
The thyroid gland is an endocrine gland in the
neck consisting of two lobes connected by an isthmus.
It is a large ductless gland in the neck that
secretes hormones regulating growth and development
through the rate of metabolism....
, INTRODUCTION:
The thyroid gland is an endocrine gland in the
neck consisting of two lobes connected by an isthmus.
It is a large ductless gland in the neck that
secretes hormones regulating growth and development
through the rate of metabolism.
The thyroid gland is found at the front of the
neck below the Adam`s apple.
, Thyroid gland anatomy:
• The Thyroid Gland is located in the anterior neck,
spanning between the C5 and T1 vertebrae.
• It lies behind the sternohyoid and sternothyroid
muscles, wrapping around the cricoid cartilage
and superior tracheal rings.
• It is inferior to the thyroid cartilage of the larynx.
,• The gland is in visceral compartment of the neck,
along with the trachea, oesophagus and pharynx.
• The compartment is bound by pretracheal fascia.
• During development, the thyroid gland initially
forms in the floor of the primitive pharynx, near
the base of the tongue.
• It descends down the neck to lie in its adult
anatomical position.
,THYROID GLAND
, Thyroid Hormones
• Principal hormones secreted by the thyroid
glands include
– Thyroxin (T4)
– Tri-iodothyronin (T3)
– T3 is also formed in the tissue by De-iodination of
T4
• Both hormones are iodine containing amino
acids
6-Nov-21 Thyroid Hormones 6
, Thyroid Hormones
I I
3’ 3
HO O CH2 – CH – C - OH
5’ 5 NH2 O
I I
3,5, 3’,5’ Tetraiodothyronine (T4)
I I
3’ 3
HO O CH2 – CH – C - OH
5 NH2 O
I
3,5, 3’ Tri-iodothyronine (T3)
6-Nov-21 Thyroid Hormones 7
, Thyroid Hormones
• Small amount of reverse tri-
iodothyronine (RT3) can be formed
– 3,3’,5’ tri-iodothyronine
• T3 is more active than T4
• RT3 is inactive
6-Nov-21 Thyroid Hormones 8
, Synthesis of the thyroid hormone
• Synthesis of thyroid hormone takes place in the
thyroglobulin, present in follicular cavity.
• Iodine and tyrosine are essential for the formation of thyroid
hormones.
• Iodine is consumed through diet and absorbed from the GI
tract.
• For the synthesis of normal quantities of thyroid hormones,
approximately 1mg of iodine is required per week or about
50mg per year.
,
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