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Thyroid gland
By
Raaj Aswini and Sai Paavani

 The thyroid gland is a butterfly-
shaped organ and is composed of two
cone-like lobes or wings, lobus dexter
(right lobe) and lobus sinister (left
lobe), connected via the isthmus
 Each lobe is about 5 cm long, 3 cm
wide and 2 cm thick
Its size depends on:
1. age … age   size.
2. sex … female > male.
3. physiological condition …

 It starts cranially at the oblique
line on the thyroid cartilage (just
below the laryngeal prominence, or
'Adam's Apple'), and extends
inferiorly to approximately the
fifth or sixth tracheal ring.
 The thyroid gland is covered
by a thin fibrous sheath, the
capsula glandulae thyreoideae,
composed of an internal and

 The thyroid is one of the larger
endocrine glands, weighing 2-3
grams in neonates and 18-60 grams
in adults, and is increased in
pregnancy.
 It participates in these processes
by producing thyroid hormones, at
3–4 week of gestation.
 The thyroid gland appears as an
epithelial proliferation in the floor

 Thyrotropin-releasing hormone (TRH)
and thyroid-stimulating hormone (TSH)
start being secreted from the fetal
hypothalamus and pituitary at 18-20
weeks of gestation.
 Fetal production of thyroxine (T4)
reach a clinically significant level at
18–20 weeks.
 Fetal triiodothyronine (T3) remains
low (less than 15 ng/dL) until 30
weeks of gestation, and increases to
50 ng/dL at termClinical significance

 Thyroxine (T4) or
tetraiodothyronine
andTriiodothyronine (T3) are
Secreted by Follicular cells.
 they Can be stored in thyroid gland
for couple of months (2-3 months).
 Having significant effect on
metabolic rate of the body
 93 % of Thyroxine (T4) or
tetraiodothyronine and 7% of
Triiodothyronine (T3) are secredted

 Almost all T4 is converted into T3 in
tissues
 T3 is the active form of T4.
 T3 4 times > potent
(active/important) than T4 in
tissue, but it present in much
smaller quantities in
blood, & persists for a much shorter
time than does T4.

 Almost all THs are carried in the
blood, mostly in an
inactive form, bound to 3
different types of proteins:
a. Thyroxine binding globulin
… 80%
b. Thyroxine binding pre-
albumin … 10%
c. Plasma albumin (serum

1.GOITER:
 1.it is a small harmless
disorder
 it is the swelling of neck or
larynx resulting from
enlargement of thyroid gland
 Goiter is caused by iodine
deficiency
 Small doses of iodine in the

 there are two types of disorders
depending on the
abnormal production of thyroid
hormones
 Too much thyroid hormone
results in a condition known as
hyperthyroidism , this can result
due to several disorders such as
 Toxic adenomas: Nodules develop in the
thyroid gland and begin to
secrete thyroid hormones,

 Subacute thyroiditis: Inflammation of the
thyroid that causes the gland to
"leak" excess hormones, resulting
in temporary hyperthyroidism that
generally lasts a few weeks but
may persist for months.
 Pituitary gland malfunctions or
cancerous growths in the thyroid
gland can also result in
hyperthyroidism , so the excessive

GRAVE’S DISEASE
 Graves' disease is an autoimmune
disease.
 It causes thyroid to enlarge to
twice its size or more
 symptoms such as increased
heartbeat, muscle weakness,
disturbed sleep, and irritability. It
can also affect the eyes, causing
bulging eyes (exophthalmos).It

 Normally, the thyroid gets its
production orders through another
chemical called thyroid-stimulating
hormone (TSH), released by the
pituitary gland in the brain. But in
Graves' disease, a malfunction in
the body's immune system releases
abnormal antibodies that mimic
TSH. Spurred by these false signals
to produce, the thyroid's hormone

 an underproduction of thyroid
hormones causes hypothyroididsm
,which is also caused due to several
other disorders such as
 Hashimoto's thyroiditis: In this autoimmune
disorder, the body attacks thyroid
tissue. The tissue eventually dies and
stops producing hormones.
 Removal of the thyroid gland: The thyroid may have
been surgically removed or chemically
destroyed.
 Exposure to excessive amounts of iodide: Cold and sinus
medicines, the heart medicine
amiodarone, or certain contrast dyes

 Lithium: This drug has also been implicated
as a cause of hypothyroidism.
Untreated for long periods of time,
hypothyroidism can bring on a
myoxedema coma
 Myxedema :
 it is caused by an accumulation of
tissue products such as
glycosaminoglycans, in the skin.
 Symptoms of myxedema include
thickening of the skin , fatigue, weight
gain, depression, dry skin, and brittle
hair, Skin thickening or swelling
associated with myxedema is often

 A lack of thyroid hormones in the
system at an early age can
 lead to the development of
cretinism (mental retardation) and
dwarfism (stunted growth).
 Cancer of the thyroid gland is
quite rare and occurs in about 5%
of thyroid nodules. People who
have received radiation treatment
to the

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