mnsr 37 Flashcards
thyroid gland is attached to the — and downgrowth is from the floor of the — and it weighs — and its highly —
- larynx
- pharynx
- 25 grams
- vascularised ( which has greater blood supply than kidney and is 2nd only to adrenal gland in blood flow )
a — is a bi-lobed structure with one love either side of the trachea
thyroid gland
each follicle consist of fluid filed spaces surrounded by a layer of — and these spaces are filled with jelly like substance called —- and it consist of — , surrounded by highly vascularised connective tissue lightly stained with — , they are held together by — which is a connective tissue supporting the follicles
follicular cells , colloid ,thryoglubin which is a protein prosecutor to the thyroid hormone , follicular cells , stroma
TRS is released by —
TSH is released by —
hypothalamus
anterior pituitary which promotes the release of T3 , T4
T3 + T4 :
has +ve effect on :
-ve effect on :
- +ve on the target organ and -ve on hypothalamus and pituitary
Acumalation and storage of — is essential for the production of thyroid hormone .
Active — are located — membrane of the —
- iodine and its ingested in small quantities in our diet ( 150 ug is suffiencet in diet )
- idoine pump is located outside the membrane of the follicular cells
the uptake of iodine is partially under the control of the —-
pituitry hormone TSH ( thyroid stores 4,000 ug of iodine )
– stimulates follicular cells to increase the uptake of — from the bloodstream , the follicular cells pumps the iodide into the —-
TSH , idoide , follicular spaces
Iodide (I -) is oxidised by — to from —
TPO ( thyroid peroxidase ) , Iodine (I2)
— is a prosecutor to thyroid hormone and produced within the follicular cells and forms —
thyroglobulin (Tg) , homodimers
( each thryroglobulin has 140 tyrosine amino acids)
hormone formation process :
1- the oxidation of iodide to iodine by the enzyme TPO
2- after they get released into the follicular cells they iodine binds to tyrosine amino acid residue of the thryoglibulin folicule
3- each tyrosine has two or one iodine attached to form MIT ( monoiodotyroxine ) or DIT ( diiodotrysoine ) , these remain attache to the Tg protein
4- peroxide combines 2 DIT and produce T4 more than T3
5- throyglobin remains in the colloid until TSH stimulates the endocytosis of the colloid back to the follicular cells
5- protease will cleave T3 and T4 and hormones will be released into the bloodstream
5- the rest of Tg protein will be degraded and any iodinated tyrosine not incorporated in T3 or T4 is recycled
Peroxide is more efficient at combining — which makes — generation more easily thus the thyroid gland produces more – -than —
- 2 DIT
- T4 more readily
- T4 more than T3
thyroid also contains smaller amount of — which are also called – and they produce —
- parafollicular , c-cells , calcitonin
peroxidase will form — between iodanated tysoine
covelant bonds
2 DITS forms
T4
1 MIT and 1 DIT forms
T3
I2 + tyrosine froms
monoiodotyrosine or diiodotrysoine ( T1 or T2 )
– is more potent of two hormones up to 40 times
T3
plasma half life of T4 is – while T3 is —
- 6 days
- 1.3 days
T3 enters the cells of the — and causes direct activation of —-
target organs , dna transcription in the nuclease
once inside the cells most of the thryroxine will be de-iodinated to — (80%) or reverse – which is — (20%)
- T3 , T3 , inactive
up to 90% of the biologically active thyroid hormone is —
T3
the ratio of hormones in the blood stream is —
majority of these hormones are bounded to —
- 10:1 , 90: thyroxine and 10% T3
- serum proteins including thyroxine , globulin , and albumin
Bound T3/T4 is — only free thyroxine and T3 can —-
inactive , enter the target cells
the protien-bound thyroxine serves as a —
reservoir in blood
carrier proteins have higher affinity to – which is why the proportion of T3 ion the plasma is in free/unbounded state has — times greater than —-
- T4 than T3
- 10 times than T4 in free state
( final circulation will have 90 ug and 40-60 ug of T3 since thyroxine will be de-ionated to t3)
the effect of thyroid hormones :
- increase the basal metabolic rate (amount of energy expended in rest)
- promotes growth and mutaration
- specific physological effects
the effects of thyroid hormones of metabolic rate:
- increase it from 60 to 100% where hormones will be released
- increase 02 consumption
- increase protein synstheis , rna sythesis so more rna and mrna , metbabolic enzymes will increase and mitochondria increase the ATP levels
thyroid gland works synergically with —- on the bone growth
low level of the enzyme will lead to — but parodixally high levels of the enzyme will lead to —
- insulin like growth factor ( IGF-1 )
- poor growth and retarted sexual development in puberty
- rapid pardoxally growth at first buy stops at younger bc because of early closure of epiphysis
the normal development of the CNS before and after birth depends on the aduquent level of —
thyroid hormones
physiological effects of thyroid hormone
- carbs and fat metabolism is increased so increased levels of lipids
- may decrease body weight but enhanced apetite
- cardiac output increases so high systolic pulse pressure
- GIT secretion increased and enhanced mobility
- CNS as: nervousness , irratibilty, muscle tremor , constant tiredness and unable to sleep
under active thyroid is — and produces insufficient levels of thyroid caused by — iodine and in children it may lead to — and in adults —
causes: —
treatment for primary :
treatmenr for secondary :
- hypothyroidism
- low idoine
- cretinism aka congenital iodine deficney syndrome ( poor growth and dwarf stature , decreased thyroid activity before and after birth due to failure of development of the CNS )
- myxoedema : thickens skin , hair loss m conga in facial appearance , goitre , muscle stiffness
- iodine defecincy, yo-yo diet m overactive adrenal gland , hasmimoto thyroiditis , autoimmune which causes self destrcuture of thyroid cells , more common in females (80%)
- primary : thryoid hormone
- secondary : aleviate symptoms
– refers to 5-10 higher than normal and most symptoms are under —- as: —–
causes are: —
(CHECK SLIDE 32)
- hyperthyroidism
- physiological effects
- hypertension , raised body temp, weight loss and may be accompanied by protrusion of eyeballs called: exophthalmos
- cause includes: graves disease 70-80% etology , toxic multidular goitre , toxic thyroid adenoma which is the hyper functioning follicle due to adenoma
Graves disease is a cause of — and it occurs due to —–
- hyperthyroidism
- auto bodies to TSH , antibodies stimulates receptor and leads to increase secetion of T3 and T4
— is enlargement of thyroid and may occur in ——
- goitre
- hypo, hyper, normal thyroid
— is the bulging of the eye anteriorly out of orbit and retro-orbital oedema and fat demposition
exophthalmos
exophthalmos is symptom of —
graves diseases and not hyperthrydosim
