thyroid gland Flashcards
where is thyroid found
front of trachea
-largest gland in neck
2 thyroid glands attached by
isthmus
-typ asymmetrical
what gender is thyroid larger in
women
-controls more hormonal activity
as thyroid develops incorporate
C cells
-parathyroid glands attached to back of thyroid
major structural unit
thyroid follicle
-capillary’s in between follicles
Thyroid gland has continually ______ flow to bring nutrients that are needed into the area
blood
in order for glands to work properly need
iodine
-only gland in body that uses this
-get from diet
All follicles are surrounded by gel like material
colloid
Main component of colloid
thyroglobulin
-this glycoprotein made only in the thyroid and is important in function
Main function of follicles is to
take in, concentrate, and use the iodine
-we need iodine to make thyroid hormones
iodine + _______ = thyroid hormones
tyrosine
2 main thyroid hormones
T3= triiodothyronine
T4= thyroxine
-released into bloodstream where control many metabolic rxns
T3
triiodothyronine
T4
thyroxine
feedback loops starts in the
hypothalamus
-releases thyroid releasing hormone (TRH)
after hypothalamus kicks the
pituitary gland to release TSH (thyroid stimulating hormone)
what is TSH also known as
thyrotropin
after pituitary kicks
thyroid gland to release T3 and T4
When T3 and T4 high enough go back to
hypothalamus to turn off
thyroid can store iodine for
2-3 months if we don’t have enough exposure to it
If you come in contact with radioactive iodine in some cases of cancer treatment, nuclear activity, body can store
radioactive iodine
-if frequent exposure can lead to thyroid cancer
5 steps in formation
- trap iodine
- organification
- coupling stage
- storage
- secretion
what is organification
oxidize to active form by the thyroid peroxidase enzyme
what does organification result in
production of monoiodothyronine (MIT) and diiodothyronine (DIT)
thyroxin (t4) made of
coupling of 2 DIT
triiodothyronine made of
coupling of 1 MIT and 1 DIT
where thyroid hormones stored
thyroid particles
most abundant thyroid hormone
T4
-precursor to T3
so T4 can be made into T3
most metabolically active hormone
T3
-main involved in metabolic rxns
if too much T4 will be made inactive
into rT4 (not metabolically active)
When T3 and T4 released into bloodstream
only a small fraction will remain free, majority will be bound
biologically active form is
free form
3 main binding hormones
-thyroxine binding hormone (TBG)
-prealbumin
-albumin
main component of TBG
T3 and T4 are bound
prealbumin also called
transrethyin
Most T3 and T4 are bound to
proteins
-so very affected by protein levels
-low albumin= more circulating T3 and T4
when measuring we are measuring
free levels
most common thyroid disorder/ primary hypothyroidism
hypothyroidism
-aka hashimoto’s
-more common in women
-age 40
2 antibodies produced in Hashimoto’s
Anti-microsomal
Anti-thyroglobulin
anti-microsomal now called
peroxidase Abs
symptoms of hypothyroidism
Fatigue
Weight gain
Hair loss
Elevated lipids, high cholesterol
Rubbery goiter
Cold intolerance
Inappropriate increased levels of ADH
Decreased levels of sodium
in hypothyroidism, TSH is
increased
-thyroid gland is not producing T3 and T4 so pituitary gland in producing more TSH for production
in hypothyroidism, T3 and T4 will ne
decreased
-always follow disease state
most doctors will start testing
TSH
-not good because normal levels can be abnormal for you
treatment for hypothyroidism
synthetic T4
T4 is precursor for T3
what occurs if hypothyroidism is not treated
myxedema
what is myxedema
Accumulation of glycosaminoglycans and other mucopolysaccharides
-thickening and swelling of the skin
-affects face and legs
-scarring
what is seen by insufficient thyroid hormone since birth
cretinism
creatinism is also called
Congenital hypothyroidism
-born to hypothyroid mothers who are not being treated
features of creationism
Short, increased body weight, tongue out, mental impairment, infertile, blind and deaf
why is creatinism not seen in the US
every baby is tested for T4 levels at birth
-if low are given T4 from birth to prevent the results
