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Chen Hui Lin
THYROID DISEASES
AND
NUCLEAR
MEDICINE
The thyroid,
an
important
hormonal gland,
is
situated
in
front of
the
lower neck.
lt
has
extensive
functions:
in
the
infant,
it
promotes
brain
development, nervous
mechanism
initiation and development, as well
as
physical and mental
groMh.
Deficiency
results
in
permanent mental and physi-
cal
retardation.
Thyroid
hormones
that
are stored
in
the follicles, are controlled
by a
"trophic"
hormone,
thyroid
stimu-
lating hormone (TSH),
in
turn
secreted
by
the
master gland
-
the
pituitary.
lnadequate thyroid hormone induces
TSH secretion,
a
positive or stimulatory
feedback and vice versa.
ln
the
adult,
iodine deficiency results
in
gland
enlargement (goiter).
Pathological
goiters are commonly due to thyrotoxi-
cosis
or
excessive
hormone
secretion
(ditfuse goiter); nodular goiters usually
have normal thyroid function.
Thyroid
dysfunction
may be physiological, due
to excessive demand during puberty
or
pregnancy or breast leeding;
organic,
due
to
space occupying lesions
or
inflammatory,
e.9.,
Hashimoto's
thyroiditis, is
due
to
auto-immunity
(self-inflicted immune attack
on the
gland).
Thus,
high serum
TSH
usually
means inadequate thyroid function and
vice versa
-
the latter is also associ-
ated
with
high
serum thyroid hormones,
especially
the'T3"
type.
The significant
role of nuclear medicine
for
thyroid
is
based on
the dynamic real-time
map-
ping of swallowed
traceable
quantities
of radioactive iodine-131
.
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