Thyroid Disease Flashcards
What are the serum thyroid markers?
TSH: Thyroid-Stimulating Hormone
T4: Thyroxine
T3: Triiodothyronine
What is TSH/what does it do? How is it used in relation to diagnosing/monitoring thyroid disease?
TSH:
- produced by the anterior pituitary gland
- an endocrine MESSENGER
- most sensitive measure of thyroid disease ***
What is T4 and what are the forms of it? Describe them.
T4 is made by the thyroid gland.
3 forms:
- Bound T4
- Free T4
- Total T4 = Bound T4 + Free T4
Bound T4:
- IS attached to proteins
- IS NOT effective because it’s too large to enter cells
Free T4:
- IS NOT attached to proteins
- IS effective because it can enter cells
Describe T3 and its forms.
3 forms:
- Bound T3 is bound to proteins
- Free T3 is not bound to proteins
- Total T3 = Bound T3 + Free T3
Bound T3:
- about 99.5% of Total T3 circulates as Bound T3 &
- serves as a reserve
Total T3:
- is a more reliable measurement than Free T3
What is the approximate ratio of T3 versus T4?
T3 is 5X more active than T4
What diagnosis is marked by:
- elevated TSH
- low T4
- normal T3?
Primary hypothyroidism
What condition would you diagnose for a patient with the following labs?
- elevated TSH
- normal T4
- normal T3
Subclinical hypothyroidism
What diagnosis is appropriate for the following labs:
- low TSH
- elevated T4
- normal T3?
Primary hyperthyroidism
How would you diagnose the following labs?
- low TSH
- elevated T4
- elevated T3
Primary hyperthyroidism
What is the 2nd most common endocrine problem?
Primary hypothyroidism (95% of hypothyroid cases)
What is a common cause of Primary Hypothyroidism?
Hashimoto’s thyroiditis
Describe primary hypothyroidism.
- pathology lies in the thyroid gland
- reduction in the amount of circulating thyroid hormone (T3/T4)
Describe secondary hypothyroidism.
- pathology is outside the thyroid gland
- RARE @ 5%
Should subclinical hypothyroidism be treated? If so, in what cases?
Treatment of subclinical hypothyroidism is CONTROVERSIAL!
If TSH = 10+ mU/L:
- Treat to prevent progression to primary hypothyroidism
If TSH = 4.5 to <10:
- No benefit with treatment
- Monitor 6 - 12 months UNLESS patient becomes symptomatic/more symptomatic
What medication is given to treat primary hypothyroidism and how should it be taken?
- L-thyroxine/Levothyroxine (synthetic T4)
- Given PO, in AM, on empty stomach (30 - 60 minutes before meal/other meds)
NOTE: Absorption on empty stomach varies 40% - 80% among patients
Replacement levothyroxine for primary hypothyroidism should be based on what figure?
Patient’s ideal body weight
What are the suggested initial levothyroxine doses for the following two groups of patients: young adults, middle adults (aged 50. - 60 years)?
Young adults: 1.6 mcg/kg/day
Middle adults: 50 mcg/day
What is the suggested initial levothyroxine doses for the following group of patients: older adults or patients with underlying cardiac issues or multiple comorbidities? What is the rationale for initiating and adjusting doses for this group and why?
25 mcg/day
“Start low, go slow!”
The half-life of a levothyroxine tablet is 1 week. This group could have problems with delayed metabolism of the medication and toxic levels of the medication may accumulate if dosage increases are made too quickly.
Following initiation of levothyroxine, how often and with what lab/s should patients be monitored?
- Recheck TSH every 4 - 6 weeks until euthyroid
THEN,
- Monitor TSH annually unless symptoms develop
Describe hyperthyroidism and name the most common cause of it.
Body tissues are exposed to increased level of circulating thyroid hormone (T3 and/or T4)
Most common cause: Graves Disease
How should hyperthyroid patients be handles in the primary care setting?
Hyperthyroidism should ALWAYS be referred to endocrinology!!!
