Clin Lab: Thyroid Disorders Flashcards
(64 cards)
1
Q
Draw HPA flow of HPA and thyroid gland
A
DONE
2
Q
Draw the Hypothalamic-Pituitary-Thyroid Axis
A
DONE
3
Q
Which thyroid hormone is higher in the serum?
A
T4
3
Q
List the 3 Thyroid Hormones
A
- Thyroxine (T4)
- Triiodothyronine (T3)
- Reverse T3
4
Q
How is T4 activated?
A
T4 is converted to T3 by removal of 1 iodine residue in periph tissues
4
Q
T3 half-life
A
one day
4
Q
T4 half-life
A
one week
5
Q
List the circulation transport proteins for thyroid hormones
A
- thyroxine-binding globulin (TBG)
- albumin
- pre-albumin
5
Q
If TSH is high, what could be the causes?
A
- Thyroid gland is not producing enough T4/T3
OR - Pituitary gland is releasing TSH inappropriately
OR - Very rarely, hypothalamus is releasing TRH inappropriately
6
Q
Indications for TSH testing
A
- initial screening test of thyroid function
- monitor response to tx
7
Q
If initial TSH levels are low or high what is needed?
A
additional testing to determine specific disorder
8
Q
If TSH is low, what could be the causes?
A
- Thyroid gland is making too much T4/T3
OR - Pituitary gland is not making TSH OR
- Very rarely, hypothalamus is not releasing TRH
9
Q
What level can help differentiate between primary & secondary causes of abnl TSH?
A
free T4
10
Q
What helps to TSH levels as we age?
A
it increases
11
Q
Normal range of TSH
A
4-10
12
Q
Do you measure TSH in the hospital if someone is ill?
A
NO unless you think the thyroid is causing the illness
12
Q
What can alter transiently alter TSH levels?
A
- severe illness
i.e. sepsis - euthyroid sick syndrome
13
Q
What 3 things can affect TSH levels?
A
- severe illness
- pregnancy
- high dose of biotin
14
Q
Normal range for FTI
A
1-4
14
Q
Two main ways to assess FT4
A
- Free Thyroxine Index (FTI)
–> an approximation of FT4 level - Free T4 measurement
15
Q
Calculation of FTI
A
FTI (%) = T3 Uptake X Total T4
16
Q
Is Free T4 high or low in hyperthyroidism?
A
high
17
Q
Is Free T4 high or low in hypothyroidism?
A
low
18
Q
Is FT4 harder to measure when levels are high or low?
A
low
19
Why is Free Thyroxine Index (FTI) used?
Adjusts for effects of alterations in thyroid-binding PROs on total serum T4
20
Is FTI high or low in hyperthyroidism?
high
21
Is FTI high or low in hypothyroidism?
low
22
Causes of increased Total T4 PROs
- pregnancy
- OCP
- hormone replacement therapies
- some cancers
22
Causes of decreased Total T4 PROs
- testosterone
- high dose steroids
- phenytoin
- salicylates
- cirrhosis
- malnutrition
- nephrotic syndrome
23
When is total T3 used?
primarily used as a confirmatory test of hyperthyroidism
24
What to order next if TSH in high?
Free T4 OR Total T4/T3 uptake/Free Thyroxine Index
25
When should you check TSH level after a dose adjustment?
6 weeks
25
What to order next if TSH in low?
Free T4 OR Total T4/T3 uptake/Free Thyroxine Index and Total T3
26
List the autoimmune labs
Antithyroglobulin & Antithyroperoxidase Ab
- Anti-TSH receptor Ab
27
If you suspect Hypothyroidism (Hasimoto's), which test should you order?
Antithyroglobulin & Antithyroperoxidase antibodies
28
If you suspect Hyperthyroidism (Graves Dz), which test should you order?
Anti-TSH receptor antibodies
29
Indications for thyroid uptake scan
- Thyroid nodule / enlarged thyroid on exam
- Hyperthyroidism
**when you think cancer**
29
Why is it called a "hot" nodule?
because the nodule has an increase metabolism & uptakes the tracer more
30
Contraindications of thyroid uptake can
- pregnancy/breast feeding
30
Which type of thyroid nodule is more concerning of cancer?
cold nodule
31
Indications for an US w/ biopsy
- Thyroid nodule on exam or on other imaging
- Assessment of goiter (diffusely enlarged thyroid)
- Fine needle biopsy guidance
- Assess lymph nodes surrounding thyroid
- Preop planning for thyroidectomy
32
S/Sx of hypothyroidism
- cold intolerance,
- fatigue
- constipation
- weight gain
- thin brittle hair
- lose lateral eyebrows
- dry skin
33
Cause of Primary hypothyroidism (95%)
- thyroid doesn't produce thyroid hormone
- Most common cause is chronic autoimmune thyroiditis (Hashimoto)
34
Cause of secondary hypothyroidism
- anterior pituitary doesn't secrete sufficient TSH
- Most common cause is pituitary adenoma
35
Cause of Tertiary hypothyroidism (RARE)
- hypothalamus doesn't produce sufficient TRH
36
Initial testing for Hypothyroidism? Expected results?
TSH expect it to be high
37
FU testing for hypothyroidism Expected results?
Free T4 should be low
38
Optional FU testing for hypothyroidism
- Anti-thyroglobulin (40% of pts) & Anti-thyroid peroxidase antibodies (90% of pts)
+/- imaging
39
Test Results Chart - Hypothyroidism
DONE
40
Test Results Chart - Subclinical Hypothyroidism
DONE
41
What should be done if pt is asymp + with TSH >10
monitor serial labs
42
When should you tx a pt >65 yo?
treat if TSH >6.9 (7)
43
When should you tx a pt <65 yo?
treat if > upper limit of normal
44
What endocrine condition is associated with increased lipids?
hypothyroidism
45
S/Sx of hyperthyroidism
- tachycardia
- heat intolerance
- anxiety
- palpitations
- Afib
- tremor
- sweating
- warm skin
46
Causes of primary hyperthyroidism
- overproduction of thyroid hormone
Most common causes:
- Diffuse Toxic Goiter (Graves’ dz)
- Toxic Multinodular Goiter (Plummer’s dz)
47
Causes of 2ndary hyperthyroidism
- Overproduction/inappropriate production of TSH by anterior pituitary
- Most common cause is pituitary adenoma
48
Causes of tertiary hyperthyroidism
RARE!!
- Overproduction/inappropriate production of TRH by hypothalamus
- Can be med-induced (amiodarone, lithium)
49
Initial testing for hyperthyroidism & expected results?
- TSH
- expect it to be **low**
50
Additional FU testing for hyperthyroidism? & is mostly commonly tested w/ which condition?
- Anti-TSH receptor antibodies (TRAb)
- Graves Dz
51
FU testing for hyperthyroidism
- free T4
- total T3
52
Imaging for hyperthyroidism
- thyroid uptake
- thyroid US
52
Hyperthyroidism Test Results Chart
DONE
52
Are there any recommended screening guidelines for thyroid dz?
NONE
