B6-060 Thyroid Gland Physiology (used Ninja Nerd instead of awful lecture) Flashcards
1
Q
synthesis of thyroid hormone begins when the paraventricular nuclei in the hypothalmus secrete […]
A
tryrotrophin-releasing hormone (TRH)
2
Q
TRH travels through the vascular connection between the hypothalmus and anterior pituitary, called the [….]
A
hypophyseal portal system
3
Q
TRH stimulates pituitary to secrete […] into the blood stream
A
thyroid stimulating hormone (TSH)
4
Q
TSH binds to the receptors on the follicles of the thyroid and stimulate it to produce […]
A
thyroglobulin (basic unit of thyroid hormone)
5
Q
[…] needs to be ingested to produce thyroid hormone
A
iodide
6
Q
how is iodide brought from the lumen into the thyrocyte?
A
via Na/I symport
7
Q
enzyme in the luminal space that performs iodine oxidation, iodination, and coupling
A
thyroid peroxidase
8
Q
3 functions of thyroid peroxidase
A
- iodine oxidation
- iodination
- coupling
9
Q
converts iodide to iodine
A
iodine oxidation (thyroid peroxidase)
10
Q
process that attaches one or two iodine molecules to thyroglobulin to create MIT or DIT
A
iodination (thyroid peroxidase)
11
Q
couples the iodinated tyrosine amino acids into T3 and T4
A
coupling (thyroid oxidase)
DIT+DIT= T4
DIT+MIT= T3
12
Q
T3 and T4 are collectively known as
A
thyroid hormone
13
Q
once iodinated, the thyroglobulin enters the thyrocyte via
A
pinocytosis –> vesicles
14
Q
the vesicles containing thyroglobulin fuse with lysosomes, resulting in
A
isolated T3 and T4
**vesicles containing isolated T3 and T4 fuse with the membrane and are released into the bloodstream
15
Q
in the blood, T3 and T4 bind to the transport protein […]
A
thyroxine binding globulin (TBG)
16
Q
TBG is synthesized by the
A
liver
17
Q
summarize the steps of thyroid hormone synthesis
A
.
18
Q
what is the structural unit of the thyroid gland?
A
follicles
19
Q
what hormone is produced by the anterior pituitary gland?
A
TSH
20
Q
which cells are stimulated by TRH?
A
follicular cells (thyrocytes)
21
Q
what does TSH activate?
A
Gs protein
22
Q
what is the main amino acid of thyroglobulin?
A
tyrosine
23
Q
what is added to thyroidglobulin during iodation?
A
Iodine
24
Q
what binds TH in the bloodstream?
A
TBG
25
enzyme that removes iodine from thyroxine
5' deiodinase
26
enzyme that converts T4 to T3 (active)
5' deiodinase
27
enzyme that converts T4 reverse T3 (inactive)
5-deiodinase
28
T3 and retinoic acid bind to the transcription factor to move into the nucleus and stimulate synthesis of
NaKATPase
**leading to production of more sodium-potassium pumps, requiring more energy=catabolic state
29
TH effects on liver [3]
glycogenolysis
gluconeogenesis
increase LDL receptors
**increases blood glucose level and uptake of bad cholesterol
30
effects of TH on heart
stimulates beta 1 receptors to increase contractility, SV, and BP
31
effects of TH on CNS
increases dendrite formation
increases myelination
increases number of synapses
**as a result, hyperparathyroidism can cause irritability
32
TH regulates bone [...]
remodeling
33
cells responsible for bone deposition
osteoblasts
34
cells responsible for bone resorption
osteoclasts
35
how does TH affect chondrocytes in the epiphyseal plates?
stimulates proliferation, hypertrophy, and ossification
**causes bones to lengthen
36
TH stimulates endochondral
ossification
37
TH effects on adipose
stimulates lipolysis
**excess glycerol converted to glucose, increases blood glucose
38
TH regulates both catabolism and anabolism.
Hyperthyroidism causes the balance to shift to [...]
catabolism
39
how does hyperthyroidism effect muscles?
catabolism causes weak, atrophied muscles/movements
40
how does TH affect the skin?
increased body temperature causes vessels to dilate it to try to cool --> skin flushed, radiates heat
increases sweat production
41
brittle nails, thin hair [hypo or hyperthyroidism]
hypothyroidism
42
thick hair [hypo or hyperthyroidism]
hyperthyroidism
43
how does TH affect the GI system?
stimulates secretion and enhances motility
44
diarrhea [hypo or hyperthyroidism]
hyperthyroidism
45
constipation [hypo or hyperthyroidism]
hypothyroidism
46
what substance is required for T3 to exert its effects?
retinoic acid
47
T3 [increases or decreases] the available ATP in the cell
decreases
**NaKATPases constantly using ATP
48
irritability [hypo or hyperthyroidism]
hyperthyroidism
49
paraventricular neurons in the hypothalmus release
thyrotropin releasing hormone (TRH)
50
TRH goes through the [...] to the pituitary
hypophyseal portal system
51
TRH stimulates anterior pituitary to release
TSH
52
TH is transported through the blood via
TBG
53
high levels of TH exert a negative feedback mechanism that
inhibits paraventricular nucleus from making TRH
-decreases TSH production
-decreases T3 and T4 production
54
low levels of TH exert a negative feedback mechanism that
stimulate the paraventricular nucleus to release excessive TRH
-increases TSH production
-increases T3 and T4 production
55
TH increases the basal metabolic rate by
increasing the number of NaKATPases
56
TH aims to increase blood glucose by stimulating [3]
lipolysis
glycolysis
gluconeogenesis
57
TH increases the uptake of [...] lipoproteins in liver
LDL (bad cholesterol)
58
TH promotes normal nerve development via [3]
increasing number of synapses
increasing myelination
increasing number of dendrites
59
triiodothyronine
T3
60
thyroxine
T4
61
converts T4 to T3 in the peripheral tissues
5' deiodinase
**5, 4, 3
62
peripheral conversion of T4 to T3 is inhibited by [3]
glucocorticoids
beta blockers
propylthiouracil (PTU)
63
proplythiouracil inhibits [2]
thyroid peroxidase
5-deiodinase- conversion of T4 to T3 in peripheral tissues
64
metabolically inactive byproduct of the peripheral conversion of T4
rT3
65
rT3 production is increased by [2]
growth hormone
glucocorticoids
66
functions of thyroid peroxidase [3]
oxidation
iodination
coupling of MIT and DIT
67
DIT + DIT =
T4
68
DIT + MIT =
T3
69
Wolff-Chaikoff effect
sudden exposure to iodine temporarily turns off thyroid peroxidase, decreasing T3/T4 production
70
[...] binds nuclear receptors with greater affinity than [...]
T3 binds nuclear receptors with greater affinity than T4
71
T3 functions:
**Seven Bs
Brain maturation
Bone growth
B-adrenergic effects
Basal metabolic rate (increase)
Blood sugar (increase)
Break down lipids
stimulate surfactant production in Babies
72
describe negative feedback of TH production
1. too much free T3/T4
2. anterior pituitary decreases sensitivity to TRH
3. hypothalamus decreases TRH secretion
73
binds most T3/T4 in the blood
TBG
74
bound T3/T4 is [active/inactive]
inactive
75
what conditions upregulate TBG? [2]
pregnancy
OCP use (estrogen)
76
what conditions downregulate TBG? [6]
androgens (**anabolic steroids**)
large doses of glucocorticoids
chronic liver disease
severe systemic illness
active acromegaly
**kidney disease with proteinuria**
77
iodide is transported into the thyrocyte via
Na/I active symport
78
where does organification/coupling occur?
in the lumen
TG then brought back into cell via endocytosis
79
once TG has been brought back into the cell via endocytosis, [...] in the lysosome convert it to free T3/T4
proteases
80
[hypo or hyper]
cold intolerance
hypohidrosis
weight gain
hypothyroidism
**due to decreased BMR, decreased calorigenesis, and hyponatremia
81
[hypo or hyper]
heat intolerance
hyperhidrosis
weight loss
hyper
**due to increased NaKATPase increasing BMR, increased calorigenesis
82
[hypo or hyper]
dry cool skin
hypo
**due to decreased bood flow
83
[hypo or hyper]
coarse brittle hair
alopecia
brittle nails
puffy facies
nonpitting edema
hypo
**due to increased GAGs in interstitial spaces increased the osmotic pressure --> water retention
84
[hypo or hyper]
periorbital edema
hypo
85
[hypo or hyper]
constipation
low appetite
hypo
**due to decreased GI motility
86
[hypo or hyper]
proximal weakness with increased CK
hypo
**hypothyroid myopathy
87
[hypo or hyper]
carpal tunnel syndrome
hypo
88
[hypo or hyper]
myoedema
hypo
**small lump rising on surface of muscle when struck with reflex hammer
89
[hypo or hyper]
abnormal uterine bleeding
decreased libido
infertility
hypo
90
[hypo or hyper]
lethargy
fatigue
weakness
depressed mood
slow reflexes
hypo
91
[hypo or hyper]
bradycardia
dyspnea on exertion
hypo
**due to decreased cardiac output
92
expected labs for hypothyroidism [3]
increased TSH (if primary)
decreased free T3/T4
hypercholesterolemia
93
[hypo or hyper]
warm, moist skin
fine hair
onycholysis
hyper
**due to increased vasodilation
94
[hypo or hyper]
pretibial myxedema
hyper
**Grave's disease**
95
[hypo or hyper]
diarrhea
increased appetite
hyper
**increased GI motility
96
[hypo or hyper]
proximal weakness with normal CK
hyper
**thyrotoxic myopathy
97
[hypo or hyper]
osteoporosis
increased fracture risk
hyper
**T3 directly stimulates bone reabsorption
98
[hypo or hyper]
abnormal uterine bleeding
gynecomastia
decreased libido
infertility
hyper
99
[hypo or hyper]
restlessness
anxiety
insomnia
tremors
brisk reflexes
hyper
**due to increased b-adrenergic activity
100
[hypo or hyper]
tachycardia
palpitations
dyspnea
arrhythmias
chest pain
systolic HTN
hyper
**due to increased b-adrenergic receptors, increased expression of NaKATPase on cardia sarcolemma
101
expected labs for hyperthyroidism
decreased TSH (if primary)
increased free T3/T4
hypocholesterolemia
102
most common cause of hypothyroidism worldwide
often presents with goiters
iodide deficiency
103
commonly caused by thyroid dysgenesis or dyshormonogenesis in utero
congenital hypothyroidism
104
pot-bellied
pale
puffy-face child
protruding umbilicus
protuberant tongue
poor brain development
6 Ps of congenital hypothyroidism
105
caused by a shift in conversion of T4 from T3 to rT3 (inactive)
non-thyroidal illness
106
decreased T3 with normal or low T4/TSH in a critically ill patient
non-thyroidal illness
107
self limited disease preceded by viral illness
subacute granulomatous thyroiditis (de Quervains)
108
thyroid replaced by fibrous tissue and inflammatory infiltrate
Riedel
109
autoimmune disease that attacks/destroys the thyroid gland
Hashimoto's
110
rare but occurs due to sporadic mutation in thyroglobulin or TPO
sporadic goiter
111
treatment for hypothyroid disorders
exogenous L4 (levothyroxine)
112
autoimmune disease that destroys TSH-R preventing negative feedback onto TSH production
Graves
113
most prevalent autoimmune disorder in the US
Graves
114
occurs in 50% of Graves patients
ophthalmopathy
115
excessive quantities of TH
thyrotoxicosis
116
adenomas of the thyroid gland cause [...] hyperthyroidism
primary
117
pituitary adenomas cause [...] hyperthyroidism
secondary
**due to excessive TSH secretion
118
PTU inhibits [2]
type 1 5'deiodinase
TPO
119
carbimazole/methimazole inhibit
TPO
120
treatment for hyperthyroidism [4]
radioactive iodine
thyroidectomy
drugs -PTU, carbimazole/methimazole
beta blockers for heart effects
121
[hot or cold nodule]
take up radiotracer
hot
122
[hot or cold nodule]
secreted thyroid hormone
hot
123
[hot or cold nodule]
ablate with radiotracer
hot
124
[hot or cold nodule]
nonfuctional-do not take up tracer
cold
125
[hot or cold nodule]
non-secretory
cold
126
[hot or cold nodule]
increased association with malignancy
cold
127
[hot or cold nodule]
require FNA cytology
cold
128
younger patients with thyroid deficiency secondary to lack of iodine present with [2]
growth delay
neurologic impairment
129
pretibial myxedema
exophthalmos
Graves disease
130
in Graves, radionucleotide scan will display
increase in tracer uptake
131
after thyroidectomy, patients must be treated with levothyroxine to prevent
symptoms of hypothyroidism
132
anti-thyroglobulin and anti-thyroid peroxidase are associated with
Hashimoto
133
lymphocytic infiltration with well-developed germinal centers and Hurthle cells
Hashimoto
134
which drug used to treat hyperthyroidism is safe in pregnancy?
PTU
135
definitive treatment of hyperthyroidism is accomplished with [2]
surgical thyroidectomy
radioactive iodine ablation
136
medications for initial treatment of hyperthyroidism [2]
methimazole
PTU
137
mental retardation
protruding tongue
slow movements
coarse facial features
congenital hypothyroidism
138
congenital hypothyroidism is caused by
impaired production of T4
**causes increased production of TSH
139
rare but severe side effect of PTU
agranulocytosis
140
MOA of PTU
inhibits peripheral conversion of T4 to T3
