IBSS 1540
IBSS 1540 Exam 2025 Study Guide
What are two aspects about the thyroid gland's anatomy that hint to you that it is a very
important organ? - --the gland is well vascularized
-it is one of the largest endocrine glands
What makes up the colloid found within the follicles of the thyroid gland? - -thyroglobulin
What is the function of the parafollicular cells in the thyroid? - -they make calcitonin
What two dietary components are required in order to synthesize thyroid hormone? - -
tyrosine and iodine
What is the role of NIS in the synthesis of thyroid hormone? - -it is a sodium iodide
symptorter that binds both molecules in order to bring them into thyroid cells
What is the role of TSH in regads to NIS in the synthesis of thyroid hormone? - -TSH
activates the NIS symptorter, there by helping import iodine into thyroid cells to
synthesize hormone with
What happens to iodide once it enters the thyroid cells? - -it migrates towards the colloid
and enters through a transporter
What reaction is catalyzed by thyroid peroxidase in the synthesis of thyroid hormone? -
-it converts 2 I-, hydrogen peroxide, and two protons into iodine and 2 molecules of
water
Why is iodine so important in the synthesis of thyroid hormone? - -it reacts with tyrosine
residues found on the thyroglobulin in the thyroid follicle's colloid
Which enzyme in the synthesis of thyroid hormone oxidizes iodide and adds iodine to
tyrosine? - -thyroid peroxidase
What is the role of TSH in the synthesis of thyroid hormone? - -it stimulates thyroid
peroxidase, an enzyme involved in synthesizing iodine and adding it to tyrosine on
thyroglobulin. It also causes megalin to endocytose the thyroid hormone precursor into
the thyroid cells
What component of the thyroid gland synthesizes thyroglobulin? - -the thyroid cells
What is the difference between T3 and T4 in terms of their synthesis? - -T3 is formed
when a Di-iodo-thyrlobgulin is combined with MIT
T4 is formed when two DITs combine
IBSS 1540
,IBSS 1540
Which is the essential enzyme in the synthesis of thyroid hormone? - -thyroid
peroxidase
Which enzyme converts T4 to T3 in thyroid hormone synthesis? - -5'deiodinase
Why might it be helpful for 5'-deiodinase to convert T4 to T3 in peripheral tissues? - -
because T3 is a more powerful form of thyroid hormone than T4 is
How is T4 converted to T3? - -5' deiodinase removes an iodine from it
What happens if T4 reacts with 5-deidoniase instead of 5' deiodinase? - -it forms a
metabolically inactive reverse T3
Which form of thyroid hormone can only be formed in the thyroid, not peripherally? - -T4
Which thyroid hormone can be formed in the thyroid, but is mostly formed peripherally?
- -T3
Between T3 and T4, which thyroid hormone is more potent? - -T3
What are four conditions that inhibit 5' deiodinase and slow the peripheral rate of
conversion of T4 to T3? - -fasting, severe illness, high glucocorticoid levels, drugs, and
in a fetus
What is the effect of an iodine deficiency on thyroid hormone? - -there will be decreased
synthesis of thyroid hormones, which increases TSH secretion via negative feedback.
MIT is produced more than DIT due to iodine scarcity, meaning that more T3 will be
made directly in the thyroid gland
What is true of the half life of thyroid hormone? Why? - -it is very long, since most is
bound to transport proteins
What is the main binding protein of thyroid hormone? - -TBG
what two main proteins can thyroid hormone bind to? - -TBG and albumin
What portion of thyroid hormone is bound? - -over 99%
What is the effect of thyroid hormone on oxygen consumption? - -it causes it to increase
What is the effect of thyroid hormone on metabolic rate? - -int causes it to increase
What kind of hormone receptor does Thyroid hormone bind? - -a nuclear receptor
What is the effect of thyroid hormone once It binds its nuclear receptor? - -it modulates
transcription of proteins by interacting with DNA
IBSS 1540
, IBSS 1540
Thyroid hormones increases UCP levels within cells. What is the effect of this
molecule? - -it uncouples proton gradients, thereby producing heat via metabolic
reactions instead of ATP
How does thyroid hormone increase the amount of ATP produced during metabolism? -
-it increases the synthesis and activity of the sodium potassium pump
In a general sense, what is the function of thyroid hormone? - -it adjusts oxygen
consumption, ATP synthesis, and heat production to alterations in energy requirements,
supply of calories, and temperature of the environment
What are four effects that thyroid hormone has on the cardiovascular system? - -it
increases heart rate, stroke volume, cardiac output, and mean arterial pressure
What is the effect of thyroid hormone on the respiratory system? - -it increases
ventilation
What is the effect of thyroid hormone on RBCs? - -it increases their production
What is the effect of thyroid hormone on the brain? - -it is required for brain
development
What is the effect of thyroid hormone on blood flow and oxygen delivery? - -it increases
it
What is the effect of thyroid hormone on the metabolism of cabs, lipid, and proteins? - -
they increase it
Which three hormones is thyroid hormone permissive for? - -epinephrine, growth
hormone, and insulin
What is the effect of hypothyroidism on metabolism? - -it causes metabolism to
decrease
What is the effect of hyperthyroidism on metabolism? - -it causes metabolism to
increase
What is the role of thyroid hormone in children? - -it is required for normal growth and
development
What two main stimuli trigger the hypothalamus to increase TRH secretion? - -both
stress and cold
IBSS 1540
IBSS 1540 Exam 2025 Study Guide
What are two aspects about the thyroid gland's anatomy that hint to you that it is a very
important organ? - --the gland is well vascularized
-it is one of the largest endocrine glands
What makes up the colloid found within the follicles of the thyroid gland? - -thyroglobulin
What is the function of the parafollicular cells in the thyroid? - -they make calcitonin
What two dietary components are required in order to synthesize thyroid hormone? - -
tyrosine and iodine
What is the role of NIS in the synthesis of thyroid hormone? - -it is a sodium iodide
symptorter that binds both molecules in order to bring them into thyroid cells
What is the role of TSH in regads to NIS in the synthesis of thyroid hormone? - -TSH
activates the NIS symptorter, there by helping import iodine into thyroid cells to
synthesize hormone with
What happens to iodide once it enters the thyroid cells? - -it migrates towards the colloid
and enters through a transporter
What reaction is catalyzed by thyroid peroxidase in the synthesis of thyroid hormone? -
-it converts 2 I-, hydrogen peroxide, and two protons into iodine and 2 molecules of
water
Why is iodine so important in the synthesis of thyroid hormone? - -it reacts with tyrosine
residues found on the thyroglobulin in the thyroid follicle's colloid
Which enzyme in the synthesis of thyroid hormone oxidizes iodide and adds iodine to
tyrosine? - -thyroid peroxidase
What is the role of TSH in the synthesis of thyroid hormone? - -it stimulates thyroid
peroxidase, an enzyme involved in synthesizing iodine and adding it to tyrosine on
thyroglobulin. It also causes megalin to endocytose the thyroid hormone precursor into
the thyroid cells
What component of the thyroid gland synthesizes thyroglobulin? - -the thyroid cells
What is the difference between T3 and T4 in terms of their synthesis? - -T3 is formed
when a Di-iodo-thyrlobgulin is combined with MIT
T4 is formed when two DITs combine
IBSS 1540
,IBSS 1540
Which is the essential enzyme in the synthesis of thyroid hormone? - -thyroid
peroxidase
Which enzyme converts T4 to T3 in thyroid hormone synthesis? - -5'deiodinase
Why might it be helpful for 5'-deiodinase to convert T4 to T3 in peripheral tissues? - -
because T3 is a more powerful form of thyroid hormone than T4 is
How is T4 converted to T3? - -5' deiodinase removes an iodine from it
What happens if T4 reacts with 5-deidoniase instead of 5' deiodinase? - -it forms a
metabolically inactive reverse T3
Which form of thyroid hormone can only be formed in the thyroid, not peripherally? - -T4
Which thyroid hormone can be formed in the thyroid, but is mostly formed peripherally?
- -T3
Between T3 and T4, which thyroid hormone is more potent? - -T3
What are four conditions that inhibit 5' deiodinase and slow the peripheral rate of
conversion of T4 to T3? - -fasting, severe illness, high glucocorticoid levels, drugs, and
in a fetus
What is the effect of an iodine deficiency on thyroid hormone? - -there will be decreased
synthesis of thyroid hormones, which increases TSH secretion via negative feedback.
MIT is produced more than DIT due to iodine scarcity, meaning that more T3 will be
made directly in the thyroid gland
What is true of the half life of thyroid hormone? Why? - -it is very long, since most is
bound to transport proteins
What is the main binding protein of thyroid hormone? - -TBG
what two main proteins can thyroid hormone bind to? - -TBG and albumin
What portion of thyroid hormone is bound? - -over 99%
What is the effect of thyroid hormone on oxygen consumption? - -it causes it to increase
What is the effect of thyroid hormone on metabolic rate? - -int causes it to increase
What kind of hormone receptor does Thyroid hormone bind? - -a nuclear receptor
What is the effect of thyroid hormone once It binds its nuclear receptor? - -it modulates
transcription of proteins by interacting with DNA
IBSS 1540
, IBSS 1540
Thyroid hormones increases UCP levels within cells. What is the effect of this
molecule? - -it uncouples proton gradients, thereby producing heat via metabolic
reactions instead of ATP
How does thyroid hormone increase the amount of ATP produced during metabolism? -
-it increases the synthesis and activity of the sodium potassium pump
In a general sense, what is the function of thyroid hormone? - -it adjusts oxygen
consumption, ATP synthesis, and heat production to alterations in energy requirements,
supply of calories, and temperature of the environment
What are four effects that thyroid hormone has on the cardiovascular system? - -it
increases heart rate, stroke volume, cardiac output, and mean arterial pressure
What is the effect of thyroid hormone on the respiratory system? - -it increases
ventilation
What is the effect of thyroid hormone on RBCs? - -it increases their production
What is the effect of thyroid hormone on the brain? - -it is required for brain
development
What is the effect of thyroid hormone on blood flow and oxygen delivery? - -it increases
it
What is the effect of thyroid hormone on the metabolism of cabs, lipid, and proteins? - -
they increase it
Which three hormones is thyroid hormone permissive for? - -epinephrine, growth
hormone, and insulin
What is the effect of hypothyroidism on metabolism? - -it causes metabolism to
decrease
What is the effect of hyperthyroidism on metabolism? - -it causes metabolism to
increase
What is the role of thyroid hormone in children? - -it is required for normal growth and
development
What two main stimuli trigger the hypothalamus to increase TRH secretion? - -both
stress and cold
IBSS 1540
