Exam 3: Thyroid Flashcards
Explain the following 5 clinical presentations of thyroid disorders:
- Hyperthyroid
- Hypothyroid
- Goiter
- Thyroid nodule
- Abnormal thyroid function tests
- Hyperthyroid: as determined by thyroid hormone levels
- Hypothyroid: as determined by thyroid hormone levels
- Goiter: diffusely enlarged thyroid ; may or may not have abnormal thyroid hormone levels
- Thyroid nodule: focal regions of thyroid gland enlargement ; may or may not have abnormal thyroid levels
- Abnormal thyroid function tests: thyroid gland is normal; patient has symptoms of hyper or hypo thyroidism
Explain how TRH-stimulation assay is used to diagnose primary secondary or teriarty thyroid disorders
(just explain what they do)
In a TRH stimulation assay, they are trying to determine where the defecit is. Is it primary (thyroid gland), secondary (issue with pituitary), or tertiary (hypothalamus)
They give a large injection of TRH, and measure TSH levels.
Explain what the TRH stimulation test would look like for a primary thryoid disorder
For a primary thyroid disorder, TSH will already be high/ have a high baseline at administration of TRH
Also, after giving TRH, the TSH level will spike but then SLOWLY decrease. This is due to the lack of negative feedback that would normally be coming from the thyroid gland. Because the thyroid gland isn’t working, TSH won’t decrease as it should.
Explain what happens during a TRH stimulation test when the issue is a secondary thyroid disorder
Secondary thyroid disorder: issue at the pituitary
In this case, there will be NO response to TRH, and therefore undetectable TSH levels.
Explain what happens during a TRH stimulation test for a patient with a tertiary thyroid disorder
TRH stimulation test for tertiary thyroid disorder (failure at the hypothalamus)
Normal or delayed response of TSH
Protracted return to baseline
Explain what happens during a TRH stimulation test for Euthyroid sick syndrome
Euthyroid sick syndrome: nothing wrong with thyroid gland but thyroid hormone levels are low
Can be caused by starvation, anorexua, renal failure
Typically an issue with a deiodinase because reverse T3 will be high in these patients
Euthyroid Sick Syndrome TRH stimulation test: hypothyroid symptoms with low T4/T3, normal TSH and thyroid gland
The primary endpoint measured in a TRH stimulation test is ____
The primary endpoint measured in a TRH stimulation test is TSH levels
Diagnostics: Radioactive Iodide takeup scan:
Iodide is taken up into ______ cell
Iodide is transported by the ______
Radioactive iodide and anions like pertechnetate (TcO4) can be transported by _____
This radioactive iodide takeup scan test is used to determine ________
Diagnostics: Radioactive Iodide Takeup Scan:
Iodide is taken up into thyroid epithelial cel
Iodide is transported by the sodium iodide transporter (NIS) in the epithelial cells
Radioactive iodide and anions like pertechnetate (Tc04) can be transported by NIS
This radioactive iodide takeup scan test is used to determine function of the thyroid gland
Explain cold nodules vs hot nodules within the radioactive iodide uptake scan
Cold Nodule: there is a space where the thyroid follicle cells aren’t working, obvious open space on the scan, cold nodules are more predictive than malignancy than hot ones are
Hot nodule: follicles are overreactive in one spot (one dark spot)
Diagnostics: Radioactive Uptake Scan:
Normal uptake is ___ after 24 hours
> ___ is hyperthyroid
< ____ is hypothyroid
Accelerated turnover is seen in hyperstimulated thyroid gland (i.e.________)
Explain what that means
Diagnostics: Radioactive Uptake Scan:
Normal uptake is 25% within 24 hours (this is due to the wolf chaikoff effect)
> 60% is hyperthyroid
< 5% is hypothyroid
Accelerated turnover is seen in hyperstimulated thyroid gland (like in Grave’s Disease)
In grave’s disease, the TSH receptor is overstimulated… causing rapid uptake of iodide, rapid synthesis of T4/T3, which gets quickly secreted back into the blood causing the dip
Diagnostics: Radioactive uptake scan
Explain what an “organification defect means”
how do you test for this?
Organification Defect: iodine cannot be incorporated into tyrosine. Test by blocking NIS with inhibitor
When thyroid peroxidase incorporates an iodine onto the TBG tyroisine residues, this is called iodination, also called “organification”
Sometimes this process gets messed up, so Thyroid Peroxidase cannot trap iodine into the cell by tagging it onto TBG, because iodine won’t be trapped, it will come right back out of cell
What does TPO do?
What kind of drug inhibits TPO?
What does reverse T3 look like compared to normal T3?
TPO adds a iodine onto tyrosine residues
If there is one iodine— monoiodothyronine
Two iodines —– diiodothyronine
T3 has the DIT on the inner ring and the MIT on the outer ring
Reverse T3: outer ring has DIT, can’t bind therefore biologically inactive
Why does the thyroid gland enlarge without iodine?
What is a goiter?
In which conditions can you get a goiter?
The thyroid gland enlarges without iodine due to feedback, excess TSH stimulating growth of epithelial cells
Goiter = enlarged thyroid
3:1 ratio of women: men with goiter
Hyperthyroid: Grave’s disease
Hypothyroid: hasimoto’s thyroiditis, iodine defeciency
Note: the presence of a goiter does not mean its hyper or hypo thyroid, could be either
What is the primary treatment for thyroid cancer?
Thyroid-ectomy
Aka take the thyroid out surgically
Explain what happens to the following things with hyper vs hypo production of thyroid thormone
Basal Metabolic Rate (BMR)
Carb metabolism (gluconeogenesis and glycogenolysis)
Protein metabolism
Lipid motabolism (lipogenesis, lipolysis, serum cholesterol)
Thermogenesis
Check the chart
for hypothyroid, everything decreases except serum cholesterol increases, cold intolerant
Hyperthyroid: everything increases except for serum cholesterol goes down, heat intolerant
Explain the effects of hyperthyroid conditions on the cardiovascular system.
What happens to cardiac output?
HR?
Can hyperthyroid cause arrthymia’s? Why?
Hyperthyroidism causes:
Increased Cardiac Output
Increased heart rate
can cause arrythymia’s because thyroid hormone increases the expression of Beta-adrenergic receptors
Explain Grave’s Disease:
What is it?
What does it do to T3/T4 levels?
What symptoms does it cause?
Note: Pak may ask about the histology slide for grave’s disease
Grave’s Disease:
Autoimmune disorder where the body produces antibodies that bind and stimulate the TSH receptors
SO the epithelial follicular cells get hyperstimulated
Elevated T4/T3 levels
Symptoms: diffuse symmetrical goiters with hyperthyroid symptoms: tachycardia, irritability, hyperactivity, heat intolerance, weight loss, nervousness, muscle wasting, bulging out of the eyes
Hashimoto Thyroiditis:
What is it?
What does it cause?
What are the symptoms?
Hashimoto Thyroiditis:;
Autoimmune destruction of thyroid follicles
Antibodies against TPO, TG
Diffuse goiter with hypothyroid symptoms: lethargy, fatigue, hair loss, cold intolerance, brittle nails, weight gain
Goiter eventually goes away
What will a histological slide look like with a patient that has hashimoto thyroiditis
Follicle cells will be collapsed and have no colloid
Explain the causes and physical manifestations and treatments for thyroid storm
THYROID STORM:
-Emergency life threatening situation
- Hyperthyroid coupled with severe acute illness (or stressor)
- Symptoms: tachycardia, high fever, altered mental status, severe nausea vomiting diarrhea, severe circulatory collapse —- resulting in death
Treatment:
PTU (only an acute treatment due to liver toxicity)
Carbimazole
Beta blockers to restore normal heart function
What does the histology slide look like for a patient with Graves Disease
Cuboidal epithelium
lots of cuboid shapes
