THYROID CANCER
THYROID GLAND, DISORDERS OF
T
this duct runs from the base of the
tongue to the
thyroid gland
.
Abnormal
development may cause the duct to
persist in its entirety or partly as a cyst.
A cyst usually becomes infected and
swollen, which may lead to formation of
a
fistula
. The cyst and any remaining
parts of the duct are removed.
thyroid cancer
Rare
tumours
of the
thyroid gland.
In most cases the cause
is unknown, although exposure to radio-
active fallout increases the risk of
developing the condition. There are sev-
eral types, depending on the type of
cells involved. In all of them, however,
the first sign is a firm nodule in the
neck, which may grow slowly or rapidly.
In many cases, the cancer is painless
and symptoms such as difficulty swal-
lowing, and hoarseness or loss of voice,
only develop when the tumour presses
on other structures. A diagnosis is made
by
thyroid scanning
and
needle aspiration
or a
biopsy
. A
thyroidectomy
is usually
followed by treatment with radioactive
iodine
to destroy any residual cancer.
Cure rates depend on the cell type and
on the size and spread of the tumour
when diagnosed. Patients need to take
thyroxine
for the rest of their lives.
thyroidectomy
Surgical removal of all
or part of the
thyroid gland
, performed
to treat
thyroid cancer
, some cases of
hyperthyroidism
,
goitre
, or a noncancer-
ous tumour of the thyroid gland.
thyroid-function tests
A group of
blood tests used to evaluate the func-
tion of the
thyroid gland
and to detect
or confirm any thyroid disorder. The
thyroid hormones T
3
and T
4
are mea-
sured, as well as thyroid-stimulating
hormone (TSH), the
pituitary gland
hor-
mone that stimulates the thyroid gland.
thyroid gland
One of the main
endo-
crine glands
,
which helps to regulate
the rate of all the body's internal pro-
cesses. The thyroid gland is situated in
the front of the neck, just below the
lar-
ynx
(voice box). It consists of 2 lobes,
one on each side of the
trachea
(wind-
pipe), joined by a portion of tissue
called the isthmus. Thyroid tissue is
composed of follicular cells, which sec-
rete the iodine-containing hormones
thyroxine (T
4
) and triiodothyronine (T
3
),
and parafollicular cells (or C cells),
which secrete the hormone
calcitonin.
T
4
and T
3
are important in controlling
the
body's
metabolism.
Calcitonin
helps to regulate calcium balance in
the body. (See also
thyroid gland, dis-
orders of; thyroid hormones.)
THYROID GLAND
thyroid gland, disorders of Disorders
of the thyroid gland may cause
hyperthy-
roidism
,
hypothyroidism
, or enlargement
or distortion of the gland.
Myxoedema
,
Graves' disease,
and
Hashimoto's thy-
roiditis
are common disorders.
Goitre
may
sometimes occur with no accompanying
abnormality of thyroid function. In rare
cases, the gland is absent at birth, pro-
ducing severe
cretinism
. Sometimes it
develops in an abnormal position in the
neck, causing, in rare cases, difficulty in
swallowing or breathing.
A genetic disorder may impair the thy-
roid's ability to secrete hormones and
goitre may result. Thyroid infection is
uncommon and leads to
thyroidtis.
Viral
infection can cause extreme pain and
temporary hyperthyroidism. Hormonal
changes during puberty or pregnancy
may cause a degree of goitre temporar-
ily. Hyperthyroidism due to excessive
production of TSH by the pituitary
gland is rare but can occur as a result of
a
pituitary tumour
.
Because iodine is necessary for the
production of thyroid hormone, its defi-
ciency may lead to goitre. Severe iodine
deficiency in children may cause myx-
oedema. (See also
thyroid cancer.)
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