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in the
front of the neck and is situated just below the larynx or
the Adams apple.
The function of the thyroid gland is to take up iodine from the foods
that we eat and to convert it into thyroid hormones namely Thyroxine
(T4) and Triiodothyronine (T3) and Calcitonin (which is involved in
calcium metabolism). The cells of this gland combine iodine and the
amino acid tyrosine to make T3 and T4. Later T3 and T4 are then released
into the blood stream and are transported throughout the body where they
control the general metabolism (conversion of oxygen and calories to
energy). The regulation of the metabolism of every cell in the body
requires thyroid hormones. The ratio of production of T4 and T3 is
80:20. However, T3 is about 4 times more potent than T4. The
production of thyroid hormones is under direct control of
the pituitary gland. Pituitary is an endocrine gland which
is situated at the base of the brain and it secretes certain
vital hormones which includes TSH (Thyroid stimulating
hormone) or Thyrotropin, besides others. When the level of
thyroid hormones (T3 and T4) falls below the required
amount, the pituitary gland secretes TSH which stimulates
increased production of T3 and T4. As the levels of T3 and
T4 keep rising in the blood, the pituitary senses this and
reduces TSH production.
The hypothalamus is that part
of the brain which produces TRH (Thyrotropin Releasing
Hormone). TRH regulates the production of TSH by the
pituitary, i.e. it has a regulatory control over the
pituitary gland. |
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