Thyroid Gland Flashcards
(124 cards)
1
Q
Shape of Thyroid gland
A
butterfly-shaped
2
Q
This separates the lobes of Thyroid gland
A
Isthmus
2
Q
How much does thyroid gland weighs?
A
15-25g
3
Q
Thyroid gland starts to produce hormones at?
A
11 week gestation
4
Q
The thyroid gland straddles the?
A
Trachea
5
Q
Cells of the thyroid gland
A
- Follicular epithelium = T3, T4
- Parafollicular cells = Calcitonin
5
Q
LARGEST ENDOCRINE GLAND
A
Thyroid gland
6
Q
What is the function of thyroid gland?
A
Produce thyroid hormones and iodine storage
7
Q
Normal Thyroid iodide to plasma iodide ratio
A
25-40:1
8
Q
Needed for Hormone synthesis
A
Iodine
9
Q
Intake of Iodine that can cause hormone secretion deficiency
A
<50ug/day
10
Q
Intake of Iodine for normal function
A
1mg/week (150ug/day)
11
Q
Absorbs iodine (ring shape)
A
Follicles
12
Q
Organized thyroid cells
A
Follicles
13
Q
Reservoir of materials for hormone production
A
Colloid
14
Q
Colloid is rich in glycoprotein….?
A
thyroglobulin
15
Q
Colloid is surrounded by?
A
Follicle
16
Q
A viscous substance
A
Colloid
17
Q
Group of thyroglobulin
A
tyrosyl group
18
Q
Thyroglobulin is rich in?
A
tyrosine
19
Q
Major component of colloid
A
thyroglobulin
20
Q
Thyroglobulin is synthesized by?
A
follicles
21
Q
Reflect thyroid mass, injury & TSH receptor stimulation
A
Thyroglobulin
22
Q
Presence of Thyroglobulin in the blood indicates?
A
Tumor (malignant/benign)
23
Thyroglobulin is increased in what conditions?
Grave's disease, thyroiditis, and nodular goiter
23
Biosynthesis is controlled by?
Thyroid-stimulating hormone (TSH)
24
Steps in biosynthesis
1. Iodide trapping/uptake (by Na-iodide symporter)
2. Oxidation
3. Iodination of tyrosyl residues by TPO (at thyroglobulin)
4. Coupling/Condensation reaction
5. Thyroglobulin is then moved to the colloid for storage
6. Exocytosis of colloid droplets
24
In Iodide trapping/uptake (by Na-iodide symporter), the iodide diffuses into the?
lumen
25
Ratio of Lumen iodide to follicular iodide
5:1
26
In oxidation, the iodide is converted to elemental iodide by?
thyroid peroxidase enzyme
26
At basal membrane of follicular cells
Iodide trapping/uptake (by Na-iodide symporter)
27
Where does the iodination of tyrosyl residues by Thyroid peroxidase (TPO) occur?
at thyroglobulin
28
Iodothyronine formed at the optical barrier, follicular cells result in?
Monoiodothyronine & Diiodothyronine
29
T4
DIT + DIT by TPO
29
T3
MIT + DIT
30
In the fifth step in biosynthesis, where is thyroglobulin moved?
To the colloid for storage
30
T4 binding proteins
99.95% T4=Plasma protein
0.05%=Free
31
How many percentages of T4 in:
- TBG
- TBPA
- TBA
- TBG: 75% of T4
- TBPA: 15-20% of T4
- TBA: 9% of T4
32
Thyroxine-binding globulin (TBG) is measured by?
immunoassay
33
These affect TBG, T4 binding
Salicylates, phenytoin, penicillin, heparin
34
How many percentages of T3 in:
- TBG
- TBPA
- TBA
- TBG: 99.5%
- TBPA: very low
- TBA: none!!!
35
Theese increase biologic activity of T3 & T4
- decreased/low affinity of T3 to binding protein
- increased or high free T3 in plasma
36
Physiologic Actions of Thyroid gland
1. Basal Metabolic Rate
2. Tissue growth – (with GH & Somatomedin)
3. CNS development
4. Autonomic Nervous System (ANS)
5. CV & Respiratory Systems
6. GIT
7. Skin
8. Lactogenesis
37
A physiological action of the thyroid for Heat generation
Basal Metabolic Rate
38
A physiological action of the thyroid that is dependent on TH in the prenatal period
CNS development
38
A physiological action of the thyroid for normal bone growth, formation & maturation
Tissue growth with GH and somatomedin
39
A physiological action of the thyroid that controls oxygen consumption and ensures oxygen delivery to tissue
Cardiovascular (CV) and Respiratory system
40
A physiological action of the thyroid for increase motility, secretion, absorption
GIT
41
Main serum carrier of T3 and T4
Thyroxine-binding Globulin (TBG)
42
A physiological action of the thyroid for increase heat production, sweating
Skin
43
This is for deiodination
Iodothyronine 5'- deiodinase
44
For T3 circulation (most abundant)
Type 1 Iodothyronine 5'- deiodinase
45
found in the brain, maintains T3 levels in CNS
Type 2 Iodothyronine 5'- deiodinase
46
Where is the Type 1 Iodothyronine 5'- deiodinase found?
Liver and kidney
47
Ratio of T4:T3 in blood
20:1
47
This is from direct TG secretion (6-7 days)
T4 (major)
48
Most of the Plasma T3-derived
- Extrathyrodial deiodination
- Liver/Kidney
- Peripheral tissue
48
T4 accounts for 80% of plasma T3
Extrathyrodial deiodination
49
This deiodinate T4
Liver/Kidney
50
T4 -> T3/rT3
Peripheral tissue
51
Inactive (high in newborns)
(reverse)rT3
51
This is more active
T3
52
TH (thyroid?) is metabolized by?
deiodination, deamination, and conjugation by glucoronic acid
52
Not useful in diagnosing hypothyroidism because levels
are not reduced until they become severe
T3
52
3rd major circulating thyroid hormone
rT3
52
rT3 is caused by the removal of?
Removal of 1 iodine from inner ring of T4
52
Half-life of T4 (T4 metabolism)
4 hrs half-life
52
rT3 is elevated in patients with?
Euthyroid sick syndrome
53
Used to assess borderline or conflicting laboratory results
rT3
54
In the Hypothalamic-pituitary-thyroid axis, if low TH it results in?
Increase TRH & TSH
54
In the Hypothalamic-pituitary-thyroid axis, if increased T3, T4 it results in?
decrease TRH & TSH
54
High serum iodide results in?
transport inhibited, high DIT, T4
55
MAJOR fraction of Organic iodine
Tetraiodothyronine (T4)
56
physiologically active form of T3 & T4
FT3 & FT4
56
Low serum iodide results in?
more absorbed, high MIT, T3
57
Indicator of thyroid secretory rate
Serum T4
57
Principal secretory product
Tetraiodothyronine (T4)
58
Increase T4 results in?
no TSH!!!
59
This is done after the hormone is separated from the protein
Immunoassay
60
With most hormonal activity
Triiodothyronine (T3)
60
How many percent of T3 from tissue deiodination of T4
(outer ring)
75-80%
61
Triiodothyronine (T3) is used for diagnosing?
T3 thyrotoxicosis
61
Indicator of recovery or recurrence of Hyperthyroidism (low in cord blood)
Triiodothyronine (T3) – “3, 5, 3’ TriIodothyronine”
62
1st seen in hyperthyroidism
Increase T3
63
Triiodothyronine (T3) is measured by?
competitive immunoassay
64
Increase T3 and T4, decrease TAG levels
HYPERTHYROIDISM
65
Signs and symptoms of HYPERTHYROIDISM
- Heat intolerance (increase sweating)
- Emotionally labile
- Tachycardia
- Unexplained weight loss
- Tremors, restlessness, hyperkinesis, anxiety,
irritability
- With diarrhea and increased appetite
65
Decrease T3 and T4, increase TAG level
HYPOTHYROIDISM
66
Signs and symptoms of HYPOTHYROIDISM
- Cold intolerance (decrease sweating)
- Bradycardia, Fatigue
- Dryness of skin
- Unexplained weight gain, dyspnea, hair loss
- Mental dullness, muscle weakness, constipation
- Yellow discoloration of skin (hypercarotenemia)
- Decrease Na+, increase CK
67
Severe hypothyroidism leads to?
Pleural and Peritoneal effusions, irregular mens, periorbital edema, myopathy, anemia
68
increase T3,T4, FT4, rT3; decrease TSH, normal TBG
Primary Hyperthyroidism
69
increase T3, T4, and TSH! (Pituitary problems)
Secondary Hyperthyroidism
70
Increase: aTPO, ATG, TBII, TSI
Primary Hyperthyroidism
70
“TSH” to compare with primary
Secondary Hyperthyroidism
70
With diffuse toxic goiter
Grave’s disease
71
With Exophthalmos and Pritibial Myxedema
Grave’s disease
71
- most common, autoimmune
- Due to circulating antibodies to TSH receptor
Grave’s disease
71
Grave’s disease is how many times more common in girls?
6x
71
Test for Grave's disease
TSH receptor antibody test
72
Low TBG = Low T4, normal FT4 and TSH
Nephrotic syndrome, Decrease Protein production
72
Low TSH, normal FT3 & FT4
- without symptoms
Subclinical Hyperthyroidism
72
Thyroid is woody/stony hard mass
Riedel's thyroiditis
73
High Estrogen = high TBG = increase binding capacity = increase total T4 and T3, normal FT4, T3 and TSH (due to negative feedback of anterior pituitary)
Pregnancy
73
Decrease T3, T4, FT4, rT3; increase TSH, normal TBG
Primary Hypothyroidism
73
with weak Thyroid-stimulating activity
Human chorionic gonadotropin (hCG)
73
Increase FT4 and T3, Low TSH
HCG after fertility
74
- Normal or increase: aTPO, ATG, TBII
- Normal to decrease: Tg
Primary Hypothyroidism
75
decrease T4, decrease TSH (Pituitary no TSH!)
- Decrease T3, FT4
Secondary Hypothyroidism
76
Decrease T3 and T4 and TSH
Tertiary hypothyroidism
77
Normal T3, T4 and FT4; TSH slightly increase
- No signs and symptoms
Subclinical hypothyroidism
77
- painful thyroiditis
- TPO antibody is absent
- Increase Thyroglobulin and ESR
Subacute granulomatous/Subacute non-suppurative
thyroiditis/ De Quervain’s
77
Also known as “chronic autoimmune thyroiditis”
Hashimoto’s disease
78
Common cause of primary hypothyroidism
Hashimoto’s disease
79
With Goiter
Hashimoto’s disease
79
In Hashimoto's disease, Thyroid is replaced by _________ sensitized T-cells bind to cell membrane causing cell Lysis and inflammatory reaction
nest of lymphoid tissue
79
Test for Hashimoto’s disease
TPO antibody = (+) increase TSH
(TPO Ab = tissue destructive disease)
80
“Cretinism”
Congenital hypothyroidism
81
- “puffy face” (moon face)
- Weight gain, slow speech
- Thin eyebrows, dry yellow skin
Myxedema
81
Peculiar nonpitting swelling of the skin. Skin infiltrated by mucopolysaccharide
Myxedema
82
- Development/functional defect of gland
- Retarded child
Congenital hypothyroidism
83
Due to severe hypothyroidism
Myxedema coma
84
These are included in the Newborn Dried Blood Spot Screening (NBS)
- Screening = low T4
- Confirmatory = high TSH
85
Acutely ill but w/o thyroid disease (low TSH = acute)
Euthyroid Sick syndrome (Non-thyroidal illness)
85
Low T3 and T4, Normal to high TSH, high rT3
- Abnormal TBG
Euthyroid Sick syndrome (Non-thyroidal illness)
