Could you please tell me three effects
that thyroid hormones (i.e thyroxine) have
on the body?
Also could you explain the concept of
'negative feedback' and how it relates to
the hormones involved in thyroxine
release?
Generally, the T3 and T4 thyroid hormones
increase metabolic activity in almost all
the cells throughout the body. Thyroid
hormones stimulate the growth of many
organs, especially the bones and the
brain.
The concept of “negative feedback”
declares that if you have two objects, the
first object will always stimulates the
second object (positive influence) but the
second object always inhibits the first
(negative feedback). An Inhibited first
object decreases the stimulation of the
second object which leads to its
inhibition. An Inhibited second object
then decreases the inhibition of the
first, which leads to stimulation of the
first again. Stimulation of the first
object then stimulates the second...and
the cycle repeats itself again.
In the case of the thyroid gland the two
components of the “negative feedback”
control mechanism are the Thyroid
stimulating hormone (TSH) and thyroxin
(T4). TSH stimulates the thyroid gland to
increase production of T4. Increased T4
then inhibits the production of the TSH by
the pituitary gland. Decreased secretion
of TSH then decreases secretion of T4.
Decreased secretion of T4 then stimulates
production of TSH by the pituitary gland.
This control mechanism control levels of
the hormone thyroxin so that they stay
within normal range in the body.
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