LMP301 Lecture 8: Thyroid Disease Flashcards
Thyroid diseases (82 cards)
1
Q
What is symptom of goiter?
A
Enlarged thyroid gland
2
Q
Is goiter due to hypo, hyper, or eu-thyroid?
A
Can be anything
3
Q
Goiter is due to…
A
Lack of iodine
4
Q
Thyroid gland secretes…
A
T3 and T4
5
Q
What is more abundant in the blood, T3 or T4?
A
T4
6
Q
What makes 2/3 of the circulating T3?
A
Peripheral tissues (liver, kidney) deiodinate T4
7
Q
What stimulates the production of thyroid hormones?
A
TSH
8
Q
What is more biologically active, T3 or T4?
A
T3
9
Q
What is the inactive form of T3?
A
rT3 (reverse)
10
Q
How is rT3 produced
A
metabolised from T4
T4 can make both T3 and rT3
11
Q
How can local thyroid status be modulated?
A
Balance production of T3 and rT3
12
Q
Thyroid hormones are needed for…
A
all tissue maturation and metabolism
13
Q
Precursor for thyroid hormones
A
tyrosine
14
Q
MIT structure
A
1 iodide attached to tyrosine
15
Q
DIT structure
A
2 iodides attached to tyrosine
16
Q
T4 is made up of
A
DIT + DIT
17
Q
T3 is made up of…
A
MIT + DIT
T4 - 1 iodine (at first benzene)
18
Q
rT3 is made up of…
A
T4 - 1 iodine (at second benzene)
19
Q
T4 is also called…
A
thyroxine
20
Q
Hypothalamus-pituitary-thyroid axis for T3, T4 control
A
Hypothalamus: TRH
a. pituitary: TSH
Thyroid: TSH binds on TSH receptor -> T4 and T3 production
21
Q
Feedback of thyroid hormones
A
TSH neg feedback on hypothalamus (short loop feedback)
T4 + T3 neg feedback on hypothalamus, a. pituitary (long loop feedback)
22
Q
How do thyroid hormones travel? Give some examples.
A
Bound to carrier proteins in plasma (e.g. albumin, TBG)
23
Q
TBG
A
T4-binding globulin
24
Q
Which thyroid hormones are active?
A
The ones not bounded to carrier proteins in the plasma
25
% of free T3 + T4
T3: 0.3% of all T3
T4: 0.03% of all T4
26
What may change the concentration of free thyroid hormones?
Changes in the [ ] or affinity of carrier proteins
27
Are FT3 + FT4 better or worse markers of thyroid function? Why?
Better
28
Effects of increasing TBG
More T4 + T3
Same FT4
Same TSH
29
What compounds increase TBG?
- estrogen
| - oral contraceptives
30
Effects of decreasing TBG
Less T4 + T3
Same FT4
Same TSH
31
Effect of inhibiting binding of thyroid hormones to TBG
Less T4
| Same FT4
32
What compounds decrease TBG?
- androgens
| - glucocorticoids
33
What compounds inhibit thyroid hormones from binding to TBG?
Salicylates
34
Myxedema
Dry, waxy swelling of the skin with abnormal deposits of glucosaminoglycans
35
Glucosaminoglycans
unbranched polysaccharides
36
What is myxedema a strong indication of?
hypothyroidism
37
key symptoms of hypothyroidism
- Weight gain
- fatigue
- myxedema
- high cholesterol
- slow HR
38
Hypothyroidism is a _____ syndrome
hypometabolic
39
What do thyroid hormones control in the body?
metabolism
40
Why is a symptom of hypothyroidisms high cholesterol?
Less LDL receptors produced, so less liver uptake
41
Types of hypothyroidism
1. Primary hypothyroidism
2. Secondary hypothyroidism
3. Tertiary hypothyroidism
42
Primary hypothyroidism
Problem at thyroid gland
43
Examples of problems at the thyroid gland
- autoimmune destruction (Hashimoto's disease)
- iodine deficiency
- treatment of hyperthyrodism
- congenital defects in hormone
- antithyroid drugs (side effect of some drug therapy)
44
Secondary hypothyroidism
Problems at pituitary gland (TSH)
45
Tertiary hypothyroidism
Problems at the hypothalamus (TRH)
46
Diagnosis for hypothyroidism:
High/normal TSH
High fT4
not hypothyroidism
47
Diagnosis for hypothyroidism:
High TSH
Low fT4
Primary hypothyroidism
48
What feature must be present for actual hypothyrodism to be diagnosed?
low fT4
49
Diagnosis for hypothyroidism:
High TSH
Normal fT4
subclinical hypothyrodism (high risk, but not yet hypo)
50
Diagnosis for hypothyroidism:
Low/normal TSH
Low fT4
Secondary hypothyrodism
51
Complications of hypothyroidism vary depending on...
When during the lifetime patient has the disease
52
Complications of hypothyroidism:
| Pregnancy
Affect fetal development (irreversible)
53
Complications of hypothyroidism:
| Infancy, childhood
- bad brain development
- can't grow tall
- low IQ
- bad psychomotor development
- cretinism (if severe)
54
Complications of hypothyroidism:
| Adult
- death from myxedema coma (if severe)
55
Myxedema coma
- long-term hypothyrodism + another factor
- cold body (<80 F)
- loss of consciousness
56
Creatinism is ____ ___thyroidism
congenital
| hypo-
57
Creatinism can be caused by...
- absence of thyroid gland
| - thyroid hormone synthesis defects
58
Is creatinism fatal?
No
- Creatinism happens if diagnosed too late
- Early diagnosis can completely reverse effect
59
Symptoms of creatinism
- mental retardation
- short
- deaf
- neurological problems
- tongue sticking out
- flat nose bridge
60
How to treat creatinism?
replacement thyroid hormone
61
Diagnosis of creatinism
screening tests for newborns (can't usually tell from clinical symptoms)
- Screen TSH (should be high if T3 + T4 is low)
- High TSH = creatinism
62
Treatment for primary hypothyrodism
Replacement therapy with synthetic T3 + T4
| - Monitor by observing TSH levels after a few weeks (should be normal)
63
Key symptoms of hyperthyrodism
- Weight loss
- Fatigue
- Glucose intolerance
- Tremor
- Infected eye
- Sweating
- Rapid heart rate
- High BP
64
Why is weight loss a symptom of hyperthyroidism?
Too much metabolic activity
65
Why is fatigue a symptom of hyperthyroidism? Why is it a symptom of hypothyrodism?
Hyper: high metabolic activity cause muscle overwork
Hypo: hormones not available, so no stimulation for metabolism
66
Causes of hyperthyrodism
1. Graves' disease
2. Plummer's disease
3. Thyroid tumour
4. Thyroiditis
5. Pituitary tumour
6. HCG secreting trophoblastic tumour
7. Iodine / iodine drugs
8. Excessive T4 + T3
67
Plummer's disease
toxic multinodular goiter:
| excess production of thyroid hormones from functionally autonomous thyroid nodules
68
Graves' disease
Diffuse toxic hyperplasia:
- Autoimmune disease that affects the thyroid
- Antibodies bind to TSH receptor
69
Thyroiditis
inflammation of thyroid gland
70
HCG secreting trophoblastic tumour
HCG has same a-unit as TSH, so during prenancy, the excess HCG might bind to TSH receptor and stimulate T3 + T4 production
71
Why might high iodine cause hyperthyroidism
Iodine is a substrate needed to make T3 and T4
72
Symptoms of Grave's disease
- retracted eyelids
73
Diagnosis of Graves' disease
- Very low TSH
- Very high fT4
- Anti-TSH receptor antibodies
- Radionucleotide uptake and scan (will accumulate in the thyroid)
74
Treatment for Graves' disease
- Antithyroid drugs
- radioiodine / radiosodium (destroy thyroid gland)
- surgery to remove thyroid gland
75
Antithyroid drugs
- Block iodide uptake
- inhibit T4 synthesis
- inhibit T4 -> T3 conversion
76
Diagnosis for hyperthyroidism:
Normal TSH
Normal fT4
not thyrotoxicosis
77
Diagnosis for hyperthyroidism:
High / normal TSH
High fT4
Pituitary tumour
| Thyroid hormone resistance syndrome
78
Diagnosis for hyperthyroidism:
Low TSH
Normal fT4
Normal fT3
subclinical thyrotoxicosis
79
Diagnosis for hyperthyroidism:
Low TSH
Normal fT4
High fT3
T3 toxicosis
80
Diagnosis for hyperthyroidism:
Low TSH
High fT4
T3 toxicosis
Primary thyrotoxicosis
81
thyrotoxicosis
hyperthyroidism
82
Why is glucose intolerance a symptom of hyperthyroidism?
Insulin is quickly cleared due to high metabolic rate
