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IHN BIOCHEMISTRY FINAL > Quiz 5: Iodine > Flashcards

Quiz 5: Iodine Flashcards

1
Q

Iodine is an __ element

A

Iodine is an ultratrace element

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2
Q

iodine deficiency disorder (IDD) is the leading cause of __

A

iodine deficiency disorder (IDD) is the leading cause of mental development disorders in young children

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3
Q

iodine deficiency promotes

A
  1. impaired cognitive development (mild –> mental retardation (cretinism))
  2. stunted growth
  3. poor school performance
  4. reduced work capacity
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4
Q

iodine deficiency also causes

A

stillbirth
miscarriage
physical impairment
thyroid dysfunction

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5
Q

biological form of iodine

A

I-

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6
Q

what is iodine a component of

A

tri-iodothyonine (T3)
thyroxine (T4)

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7
Q

main way to meet iodine requirements

A

iodized salt

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8
Q

iodine abundance in __ is varied

A

iodine abundance in soil is varied

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9
Q

when is there increased iodine RDA

A

infants
pregnancy
lactation
with age

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10
Q

A 50% increase in maternal __ is needed to maintain maternal __ and transfer __ to fetus

A

A 50% increase in maternal T4 is needed to maintain maternal euthyroidism and transfer thyroid hormone to fetus

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11
Q

why is iodine requirement increased during pregnancy? (2)

A
  1. iodine needs to be transferred to the fetus to make fetal thyroid hormones
  2. increased renal iodine clearance
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12
Q

major food source of iodine

A

bread and milk

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13
Q

variable food sources of iodine

A

beans
eggs
meats
fish

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14
Q

fortified sources of iodine

A

iodized salts

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15
Q

goitrogens promote __ which are __

A

goitrogens promote goiters which are enlarged thyroid glands

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16
Q

goitrogen = substances that inhibits __ uptake and or __ and __ release

A

goitrogen = substances that inhibits iodine uptake and or organification and thyroid hormone release

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17
Q

3 chemical goitrogens

A

goitrin
perchlorate
lithium

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18
Q

food sources of goitrogens

A
  1. cruciferous vegetables
  2. cassava
  3. millet
  4. insecticides
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19
Q

iodine toxicity is __ and causes __ issues

A

iodine toxicity is rare and causes thyroid issues

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20
Q

2 chemical food forms of iodine

A
  1. iodide (I-) bound to amino acids
  2. iodate (IO3-) in bread or iodized salts
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21
Q

where is iodine absorbed

A

upper intestine (duodenum and jejunum)

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22
Q

iodine is secreted into

A

gastric lumen

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23
Q

in healthy adults, __% of iodine is absorbed

A

in healthy adults, > 90% of iodine is absorbed

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24
Q

main iodine transporter

A

NIS

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25
NIS is dependent on __ NIS colocalizes with __ in __ NIS is inhibited by high __
NIS is dependent on **Na** NIS colocalizes with **ATPase** in **small intestine** NIS is inhibited by high **I-**
26
where is NIS found?
thyroid gland (for uptake) lactating mammary gland (secretion into milk) salivary glands and stomach cells (secretion into digestive tract)
27
NIS absorption steps
1. iodate --> glutathione --> I- 2. NIS pulls I- in, Na out 3. NaK ATPase takes Na out, K in 4. I- crosses cell to blood
28
70-80% of iodine is stored in __ (100-fold more than in __) rest in _, _, and __
70-80% of iodine is stored in **thyroid gland** (100-fold more than in **plasma**) rest in **salivary glands**, **stomach**, and **ovary and testis**
29
excretion of iodine is mainly in __(%) rest in __
excretion of iodine is mainly in **urine**(**80-90**%) rest in **feces (10-20%)**
30
__ have major mechanism to regulate iodine reabsorption
**kidneys** have major mechanism to regulate iodine reabsorption
31
synthesis of thyroid hormones steps
1. I- in blood enters basolateral via Na+/I- symporter 2. I- gose to Pendrin which sends I- out into colloid 3. ER makes thyroglobulin --> released into follicle colloid by exocytosis 4. I- --> I0 (oxidation by thyroid peroxidase) 5. thyroid peroxidase does iodination, then conjugation to make T4 6. thyroid cell endocytosis thyroid hormones, proteolysis, secretion into blood of T3 and T4
32
thyroid peroxidase function
oxidized I- to I0
33
thyroid peroxidase is a __ containing enzyme SO, __-deficiency leads to impaired __ function (__)
thyroid peroxidase is a **heme** containing enzyme SO, **iron**-deficiency leads to impaired **thyroid** function (**hypothyroidism**)
34
thyroid hormones in blood are transported by __
thyroid hormones in blood are transported by **3 proteins**
35
3 proteins that transport thyroid hormones
1. thyroid hormone-binding globulin (lowest capacity, highest affinity) 2. thyroid hormone pre-albumin (trans-thyretin) 3. albumin
36
which transporter of thyroid hormones has the lowest capacity and highest affinity
thyroid hormone-binding globulin
37
99.9% of plasma T3 and T4 are __ forms
99.9% of plasma T3 and T4 are **protein-bound** forms
38
plasma conc of __ is 50x higher than that of __ but __ is 20-100x more potent
plasma conc of **T4** is 50x higher than that of **T3** but **T3** is 20-100x more potent
39
activation of thyroid hormones is done by __ which contain __
activation of thyroid hormones is done by **iodothyroxine deiodinases (DI)** which contain **selenium**
40
__ activate thyroid hormones __ inactivate thyroid hormones
**DI1, DI2** activate thyroid hormones **DI3** inactivate thyroid hormones
41
which is the main activator of T3?
DI1
42
locations DI1 DI2 DI3
locations DI1: thyroid, liver, kidney DI2: brain, pituitary, muscle, BAT, heart DI3: cerebral cortex, skin, placenta, pregnant uterus
43
3 deficiencies that magnify effects of inadequate iodine
selenium iron vitamin A
44
__ are selenium containing enzymes
**5'-deiodinases** are selenium containing enzymes
45
iron is a component of the enzyme __ iron may also bind to T3 __
iron is a component of the enzyme **thyroperoxidase** iron may also bind to T3 **nuclear receptors**
46
vit A deficiency reduces iodine __ by __ decreases synthesis of __ decreases coupling of __ residues to form T4
vit A deficiency reduces iodine **uptake** by **thyroid glands** decreases synthesis of **thyroglobulin** decreases coupling of **iodo-tyrosine** residues to form T4
47
4 methods to generate metabolites of thyroid hormones
1. glucouronidation (T4) 2. sulfation (T3) 3. deamination 4. decarboxylation
48
all generated metabolitles of iodine are functionally __
all generated metabolitles of iodine are functionally **inactive**
49
TRH = TSH =
TRH = **thyrotropin releasing hormone** TSH = **thyroid stimulating hormone**
50
thyroid hormones genes editing
1. binding of T3 activates transcription of target genes
51
No T3 =
dozens of proteins sit on TRE deacetylated histones no trxn
52
with T3 =
T3 binds receptor, induces removal of co-repressor complex T3 recruits histone acetylases --> relaxes DNA --> trxn
53
hypothalamus releases __ to target pituitary pituitary releases __ to target thyroid T3+T4 in circulation go to (4)
hypothalamus releases **TRH** to target pituitary pituitary releases **TSH** to target thyroid T3+T4 in circulation go to **heart, liver, kidney, tissues**
54
high thyroid hormone in circulation inhibits
hypothalamus release of TRH pituitary release of TSH
55
physiological function of thyroid hormones (3)
1. regulation of basal metabolic rate 2. regulation of macronutrient metabolism 3. regulate growth and development
56
iodine regulates basal metabolic rate by effecting 2 types of processes
1. energy-producing 2. energy-consuming
57
iodine and basal metabolic rate T3 increases __ consumption
iodine and basal metabolic rate T3 increases **oxygen** consumption
58
iodine energy producing processes that are impacted
1. induce components of ETC 2. increased activity of ADP translocator into mitochondria 3. increased mitochondrial membrane area
59
energy consuming processes
1. increased heart rate 2. increased cell membrane NaK ATPase
60
how does iodine regulate macronutrient metabolism
T3 regulates metabolism of ALL macronutrients
61
T3 and carb metabolism
1. increased glycolysis and gluconeogenesis 2. increased glycogenolysis
62
T3 and lipid metabolism
1. increased synthesis of fatty acids and cholesterol 2. increased lipolysis and FA ox 3. increased biliary excretion: reduces blood cholesterol
63
hypothyroidism patients sometimes have __ cholesterol bc T3 is needed for __
hypothyroidism patients sometimes have **low** cholesterol bc T3 is needed for **cholesterol synthesis**
64
T3 and protein synthesis
1. increased protein synthesis in skeletal musc;e and heart 2. increased skeletal muscle protein turnover
65
iodine and growth and development
T3 modulates brain development and body growth
66
T3 and brain devleopment
1. neuronal axon growth, synaptogenesis 2. fetal and maternal T3 supply are essential
67
iodine and body growth
T3 controls secretion and receptor activation of GH + IGF-1
68
4 ways to assess iodine status
1. serum T3, T4, TSH (highly sensitive for infants and those at risk) 2. serum thyroglobulin (use with other tests) 3. urinary iodine (suggests mild insufficiency) 4. thyroid gland size (uniform enlargement = poor iodine intake)
69
at risk for iodine deficiency
1. pregnant 2. low I- intake, high goitrogen intake 3. ppl who don't use iodized salts 4. ppl in regions with iodine-deficient soils
70
main sign of iodine deficiency is __ due to __
main sign of iodine deficiency is **goiter** due to **thyroid hyperplasia**
71
iodine deficiency prevention
1. iodination of salt 2. potassium iodide or potassium iodate 3. milk (UK) or oil (Africa)
72
severe iodine deficiency =
cretinism
73
neurological alterations due to fetal iodine deficiency are
irreversible
74
neurological symptoms of cretinism
mental retardation deaf mutism paralysis
75
__ worsens cretinism symptoms
**selenium** worsens cretinism symptoms

IHN BIOCHEMISTRY FINAL (15 decks)

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