Thyroid Flashcards
Thyroid gland
located (above or below) the larynx on both sides and (anterior or posterior ?) to the trachea
- 2 lobes joined by an _____
- normal adult weight is __-___g
Below
Anterior
isthmus
15-20
Thyroid gland is minimally vascularized
T/F
F
Thyroid gland is made up of numerous _____
follicles
follicles are ____ in shape and lined by (single or double?) layer of cuboidal epithelium
-follicles are filled with ____
spherical
Single
colloid
follicular cells synthesize _____ and ____
thyroxine and T3
colloid is mainly made up of the (small or large?) ______ called ______ that is synthesized and secreted by the ____ and _____
Large
glycoprotein
thyroglobulin
ER wnd golgi complex
thyroglobulin has a molecular weight of ______ and contains —— _____amino acids
660000
140 tyrosine
SYNTHESIS OF THYROID HORMONE
- _____ is essential for synthesis of thyroid hormones
- minimum daily intake in food and water is ___-___mg
iodine
100-150
iodine is converted to ____ in gut and absorbed into blood and ECF
iodide
about _/3 of absorbed iodide is taken up by the thyroid while _/3 is excreted by the kidneys
1
2
STEPS INVOLVED IN THYROID HORMONE SYNTHESIS
- synthesis of _____ and its extrusion into the _____ from the ___ membrane
- _____ to pump iodine into the cell from the ____ membrane
- oxidation of iodine to ____(I to I2)
thyroglobulin
follicular Lumen
apical
iodide pump
basal
iodide
STEPS INVOLVED IN THYROID HORMONE SYNTHESIS
After oxidizing iodine to iodide
organization of iodide into ___ and _____
- coupling reaction of ___ and ___ into ___ and ____
- __cystosis of ___
MIT and DIT
MIT and DIT; T3 and T4
exo ; TG
STEPS INVOLVED IN THYROID HORMONE SYNTHESIS
After taking TG coupled with T4 and T3 back into the cell from the apical membrane
____ of T4 and T3, T4 and T3 enters the circulation
-____ of the remaining MIT and DIT. ___ and ___ is recirculated
hydrolysis
deiodination
Iodide and tyrosine
Organification of thyroglobulin
-binding of _____ with _____ in the thyroglobulin
iodine with amino acid
TG is released from the cell into the blood from the basal membrane
T/F
F
TH itself isn’t released
RELEASE of TG
-______ are cleaved from the TG molecule and released into the blood
T4 and T3
TRANSPORT of TG
- __% bind with tyrosine-binding ___
- __% bind with tyrosine binding ___
- ___% with serum ___
- less than ___% in free form
67; globulin
20; prealbumin(TBPA)
13; albumin
0.1
In the transport of T4 , ____ has the greatest affinity to bind T4
TBG
In the binding of T4, ____ has the smallest capacity to bind T4
TBG
_____ has the largest capacity to bind T4
albumin
SECRETION of TG
- normal human thyroid secretes about : *__mg of T4/day
- __mg of T3/day
- __mg of RT3/ day
80
4
2
Control of Secretion of TG
- TSH ___eases TH secretion
- T4’s feedback at ____ or ____ levels control TSH release
- cold (stimulates or reduces?) TSH
- warmth (stimulates or reduces?) TSH
- stress (stimulates or reduces?) TSH
- glucocorticoids (excite or inhibit?) TRH
incr
pituitary; hypothalamic
stimulates
reduces
Reduces
Inhibit
Stimulatory Factors of thyroid hormone
- TSH
- thyroid _____
- increased level of TBG (eg In _____)
stimulating immunoglobulins
pregnancy
perchlorate and thiocynate inhibits _____
iodide pump
iodide deficiency inhibits T4 production
deiodinase deficiency stimulates T4 production
Low iodide intake inhibits T4 production
low levels of TBG stimulates T4 production
T/F
T
F
F
F
low levels of TBG can be caused by liver diseases
T/F
T
proprothiouracil inhibits _____ enzyme
peroxidase
FUNCTIONS of thyroid hormones
- (activates or inhibits?) nuclear transcription of genes
- ___eases Na-k atpase
- ___ease number and activity of mitochondria
- promote Brain growth during ___ life and ____ years of post natal life
Activates
incr
fetal
first few
Specific functions of thyroid hormones
(A) Carbohydrate metabolism
- (slow or rapid?)uptake of glucose by cells
- ___eases gluconeogenesis
- ___eases rate of absorption from GIT
- ___eases insulin secretion
Rapid
incr
incr
incr
Thyroid hormones aid glycolysis
T/F
T
Specific functions of thyroid hormones
Fat Metabolism
- __eases mobilization of lipid from fat tissue
- ___elerates the oxidation of free fatty acids by the cells
incr
acc
Specific functions of thyroid hormones
Vitamin Metabolism
-demand for vitamins is ____eased leading to increased vitamin deficiency
incr
Thyroid hormone increases BMR
T/F
T
Specific functions of thyroid hormones
CVS
- ___eased blood flow leading to ___eased cardiac output
- __eased heart rate due to (direct or indirect?) effect on its excitability
- ___eased strength of heart muscle
incr
incr
incr;direct
incr
Thyroid hormone effect on heart muscle strength(increasing it) is depressed with marked increase in thyroid hormone
T/F
T
Specific functions of thyroid hormones
respiration
-___ease rate and depth of respiration
incr
Specific functions of thyroid hormones
GIT
- ______ appetite leading to _____ food intake
- ____ eased secretion of digestive juices
- ____eased gastric motility that can lead to ____ is in excess
enhanced
increased
incr
incr
diarrhea
Specific functions of thyroid hormones
CNS
-excess causes extreme ____ and ____ and ____
nervousness
anxiety
Worry
Specific functions of thyroid hormones
Muscles
- slight ____ in thyroid hormones leads to the hormone reacting with vigor
- muscle becomes ____ due to ____ protein catabolism
increase
weakened
excess
Specific functions of thyroid hormones
Sleep
-(easy or difficult?) to sleep
difficult
Specific functions of thyroid hormones
other endocrine glands
- ___eases the rate of secretion of most other endocrine glands
increases
Excess thyroid hormone can cause fine muscle tremor
T/F
T
Specific functions of thyroid hormones
effect on sexual function
-in men, lack of thyroid hormone leads to ____ of libido and excess can lead to _____
- in women, lack of thyroid hormones lead to __________ ,_____ period and occasionally ____
- excess in women causes ______ and ______
loss
impotence
excessive and frequent menstrual bleeding
irregular; amenorrhea
greatly reduced bleeding and amenorrhea
Infantile form of hypothyroidism is _____
- adult form of hypothyroidism is _____
- hypersecretion of Thyroid hormone causes _____ or ______
cretinism
myxedema
grave’s disease
toxic goiter
Grave’s disease
-characterized by _____ circulating levels of TSI
increased
Grave’s disease is an autoimmune disorder
T/F
T
In grave’s disease
TSI are _____ to TSH receptors on thyroid follicular cells
And when present , the TSI intensely ____ the thyroid gland resulting in __eased secretion of thyroid hormone and ___trophy of the gland
antibodies
Stimulate
incr
hyper
The follicular epithelial cells are arranged in circular follicles ____ µm in diameter
200– 300
_______ converts T4 to T3
5′-iodinase
Thyroid hormone secretion is in a pulsatile manner
T/F
F
It’s steady
Obesity increases the conversion of T4 to rT3
T/F
F
To T3
pregnancy decrease the conversion of T4 to T3
T/F
T
fasting increase the conversion of T4 to T3
T/F
F
Decr
stress increase the conversion of T4 to T3
T/F
F
Decreas
hepatic and renal failure decrease the conversion of T4 to T3
T/F
T
Thyroid hormones increase oxygen consumption in all tissues except ____,____,____
brain, gonads, and spleen
Thyroid hormones increase both protein synthesis and degradation, but overall their effect is _____
catabolic
In adults, hypothyroidism causes ____ness, (rapid or slowed?) movement, somnolence, (intact or impaired?) memory, and ___eased mental capacity.
Hyperthyroidism causes ____excitability, _____reflexia, and irritability.
listless
slowed
impaired
Decr
Hyper; hyper
if the cause of hyperthyroidism is increased secretion of TRH or TSH then TSH levels will be ____eased.
Incr
Treatment of hypothyroidism involves thyroid hormone replacement therapy, usually T__
4
r. TSH-secreting tumors are an (common or uncommon?) cause of hyperthyroidism.
Uncommon
Autoimmune thyroiditis is a common cause of hypothyroidism, in which thyroid hormone synthesis is impaired by _____ to _____, leading to decreased T4 and T3 secretion.
antibodies
peroxidase
Autoimmune thyroiditis causes goiter
T/F
T
