Thyroid phys Flashcards
1
Q
gastrulation
A
the formation of the ectoderm, endoderm, mesoderm
2
Q
mesoderm becomes
A
muscles and skeleton
3
Q
endoderm becomes
A
respiratory tract, digestive tract, liver, pancreas
4
Q
ectoderm becomes
A
outer layer of the skin, hair, lining of nose and mouth, nervous system
5
Q
facial cleft, auricular atresia, and micrognathia are due to
A
1st branchial arche and/or 2nd branchial arche
6
Q
branchial cleft cyst is due to
A
failure of one of the four branchial arches to involute
7
Q
one of the most common congenital abnormalities of the head and neck
A
branchial cleft cyst
8
Q
when will a branchial cleft cyst get larger
A
respiratory infection
grow through life
9
Q
where is a branchial cleft cyst found
A
lateral
anterior to the sternocleidomastoid
10
Q
branchial cleft cyst versus lymph node
A
branchial - fluctuant
lymph node - firm
11
Q
most common branchial cleft cyst
A
2nd branchial cleft cyst
12
Q
where does tongue originate
A
between 1st and 2nd pharyngeal arch
13
Q
outpouching between 1st and 2nd pharyngeal arch
A
foramen cecum; where the thyroid originates
14
Q
3rd pharyngeal pouch becomes
A
inferior parathyroid
15
Q
4th pharyngeal pouch becomes
A
superior parathyroid
16
Q
when does the thymus atrophy
A
with age
17
Q
most common place for thyro-glossal duct cyst
A
infra hyoid (inferior parathyroid has to traverse a further area)
18
Q
what is a sinus tract
A
an opening with drainage
19
Q
can a branchial cleft cyst or a thyroid-glossal duct cyst become a sinus tract
A
yes, they both can
20
Q
when does a thyro-glossal duct cyst move
A
when you stick out your tongue (remember than the foramen cecum is connected to the tongue originally)
21
Q
branchial cleft cysts are closely associated with
A
carotid arteries
22
Q
are branchial cleft cysts or thyro-glossal duct cysts generally painful
A
no
23
Q
where is the thyroid located
A
in the neck anterior to the cricoid cartilage
24
Q
what does the thyroid require for production of active hormone
A
iodine
25
where is thyroid hormone stored
extracellulary in the thyroid colloid
26
is thyroid hormone stored in the thyroid cells?
no; it's stored in extracellularly in the colloid
27
function of follicular cells
produce and secrete thyroglobulin into thyroid colloid
uptake of iodine via Na/I transporter
28
function of thyroglobulin
important for transport of tyrosine
important for iodinating tyrosines to develop into T3 and T4
29
parafollicular cells are also called
C cells
30
function of parafollicular cells
synthesize calcitonin
31
step 1 when creating T3 and T4
iodine comes into follicular cell via Na/I transporter
32
2nd step when creating T3 and T4
amino acids come in to form thyroglobulin (which is a protein)
33
3rd step when creating T3 and T4
thyroglobulin and iodine are transported into the colloid
34
4th step when creating T3 and T4
thyroid peroxidase (TPO) iodinates tyrosines within the thyroglobulin (we are still in the colloid now)
35
5th step when creating T3 and T4
iodinated tyrosines couple to make T3 and T4 (we are still in the colloid)
36
6th step when creating T3 and T4
thyroglobulin with iodinated tyrosines are endocytosed back into follicular cell
37
7th step when creating T3 and T4
thyroglobulin is digested by lysozymes --> release of T3, T4, rT3
release of amino acids and extra iodine for recycling
38
8th step when creating T3 and T4
T3, T4, and rT3 are diffused into systemic circulation
39
which steps are NOT stimulated further by TSH
-amino acids forming thyroglobulin
-thyroglobulin and iodine are transported in a vesicle to colloid
40
TSH exerts what type of effect
growth factor effect --> hyperplasia of thyroid
increased TSH --> growth of thyroid
41
which has a larger half life between T4 and T3
T4
42
once T3 and T4 are diffused into systemic circulation, what do they bind to
thyroid binding globulin
43
does thyroid binding globulin have a high affinity for T3 and T4
yes
44
what percent of T4 is bioavailable/free
0.02%
45
what percent of T3 is bioavailable/free
0.5%
46
Where is T4 converted to T3
in the periphery
47
what percent of circulating T3 arises from peripheral conversion
~75%
48
half life of T4
~8 days
49
half life of T3
24 hours
50
thyroid binding globulin significantly evaluates during
pregnancy
oral estrogen therapy
hepatitis
chronic heroin abuse
51
elevated thyroid binding globulin leads to what in regards to TOTAL T3 and T4
total T3 and T4 will increase
52
elevated thyroid binding gluten leads to what in regards to BIOAVAILABLE T3 and T4
nothing; stays the same; does not change
53
T4 is converted peripherally to T3 via enzymatic activity with
deiodinases
54
T3 has a HIGHER affinity for
thyroid nuclear receptors
55
Between T3 and T4, which is considered more potent?
T3
56
deiodinase enzymes
D1
D2
D3
57
where is D1 found
LIVER
KIDNEY
thyroid
skeletal muscle
58
D1 function
primarily responsible for export to plasma T3
59
what inhibits D1
calorie restriction
severe stress
60
what happens when D1 is inhibited
decreased conversion to T3 --> decreased basal metabolic rate
61
where is D2 found
CNS
pituitary
placenta
62
function of D2
primarily local effects
63
effects of calorie restriction on D2
essentially no change
D2 is found on the pituitary so local T3 will still be normal --> normal feedback loop --> no changes in TSH
64
where is D3 found
placenta
pregnant uterus
fetal tissue
brain (except pituitary)
65
function of D3
only creates rT3 which is biologically inactive
66
what hormone requirements are increased during pregnancy
thyroid hormone requirements are increased
67
when are thyroid disorders common in relation to pregnancy
during and following pregnancy
68
hCG is structurally similar to
TSH
69
since hCG is similar to TSH, it stimulates production of
thyroid hormones
70
when do we see a higher hCG
multiple gestations
71
since we have a higher hCG in multiple gestations, what can happen in regards to thyroid
hyperthyroidism (hCG is structurally similar to TSH)
72
what do we need to do with medication for patients with hypothyroidism who are pregnancy
usually increase dose
73
thyroid hormones primarily exert their effects through what pathway
genomic pathway
74
genomic pathway for thyroid hormones
thyroid hormones bind to thyroid nuclear receptors and alter gene transcription
75
thyroid hormones can also act through non-genomic pathway to enhance
mitochondrial oxidative phosphorylation --> increases energy expenditure
76
how do thyroid hormones raise basal metabolic rate
either heat production or O2 consumption
77
effects of thyroid hormones are glucose production
increased glucose production due to hepatic gluconeogenic activity
78
why do thyroid hormones not increase plasma glucose levels
pancreas increases insulin
79
how do we have increased amino acids and glycerol, which can be used for gluconeogenesis
proteolysis
80
thyroid hormones and proteolysis
thyroid hormones increase proteolysis
81
thyroid hormones and protein synthesis
thyroid hormones increase protein synthesis
82
which is increased more by thyroid hormones: proteolysis or protein synthesis
proteolysis > protein synthesis
83
effect of thyroid hormones on triglycerides
thyroid hormones increase degradation of triglycerides --> release of FA and glycerol
84
what are FA used for
fuel for liver
85
thyroid hormones and effect of lipogenesis
thyroid hormones increase lipogenesis
86
which is increased more by thyroid hormones: lipolysis or lipogenesis
lipolysis > lipogenesis
87
thyroid hormones and effect on sodium/potassium pump
thyroid hormones increase transcription of and stabilization of sodium/potassium pumps
88
how do we get heat intolerance in hyperthyroidism
increased hormone --> increase sodium/potassium pump --> increased ATP consumption --> increased oxygen consumption --> heat
89
thyroid hormones and effect on beta adrenergic receptors
increase expression and sensitivity of beta-adrenergic receptors
90
how do we get tachycardia in hyperthyroidism
increased sensitivity and expression of beta adrenergic receptors --> increased temperature and increased heart rate
increased myosin heavy chains ---> increased heart rate
91
so what chains are increased which can increase heart rate along with beta-adrenergic receptors
MYOSIN HEAVY CHAINS
92
hypothyroidism has a high chance of what in regards to lipids
high cholesterol
due to decreased lipolysis
93
what signals TRH in negative feedback loop
T3 and T4 but primarily T3!!!!
94
TSH is often ordered as
TSH with reflex to free T4
95
what is the last thyroid hormone to drop in value
T3
96
thyroglobulin is only produced by
thyroid cells and thyroid cancer cells
97
what lab test is best for monitoring for thyroid cancer recurrence after thyroidectomy
thyroglobulin
98
what lab value is present in graves disease
thyroid stimulating immunoglobulins
thyrotropin receptor antibodies
99
function of thyroid stimulating immunoglobulins
act to stimulate TSH receptors
can cause hyperplasia in graves disease
100
what lab value is present in hashimotos
thyroid peroxidase antibodies
101
function of TPO antibodies
prevent function of thyroid peroxidase --> decreased iodination of tyrosines
102
function of thyrotropin cells
responsible for production of TSH
103
function of thyrotropin receptor antibodies
decreases negative feedback loop (TRH and TSH do not get signal) --> increased thyroid hormone --> present in grave's disease
104
what is radioactive iodine imaging used when
when TSH is low and thyroid goiter or nodule are present
105
function of radioactive iodine imaging
determines if solitary nodule is hot or cold
determines if hyperthyroidism is due to thyroiditis or grave's
treatment of hyperthyroidism or thyroid cancer
106
iodine uptake in thyroiditis
minimal uptake due to decreased TSH
107
iodine uptake in graves
increased iodine uptake due to TSI mimicking TSH
108
most nodules are hot or cold?
cold nodules
109
which nodule type has a higher risk of malignancy
cold nodules
110
damage to recurrent laryngeal nerve in thyroidectomy
hoarseness, changes in swallowing
