Thyroid Disorders - Exam 3 Flashcards
TRH stands for ____ and comes from the _____. TSH stands for _____ and comes from the ______
Thyrotropin Releasing Hormone-> hypothalamus
Thyroid Stimulating Hormone -> Ant Pit
Describe the HPT axis in simplied terms
When there is no thyroid present, T3/T4 levels will _____ and TSH/TRH levels will _____
T3/T4 will decrease
TSH/TRH will increase
What will a pt with hyperthyroidism, ther T3/T4 levels will be ______ and TSH/TRH will be ______
T3/T4 will be increased
TSH/TRH will be decreased
A pt with hypothyroidism, their T3/T4 levels will be _____ and TSH/TRH levels will be ______.
T3/T4 will be decreased
TSH/TRH will be increased
_____ large glycoprotein synthesized by follicular cells of the thyroid; released into the colloid. _____ element actively absorbed by the thyroid for hormone synthesis
thyroglobulin
iodine aka no iodine no T3/T4 because it cannot be sythesized
____ enzyme; helps process iodine for use by thyroid ~1 mg/week requirement. Commonly added to table salt
Thyroid Peroxidase (TPO)
What is the difference between T3 and T4?
the number of iodine groups attached
When thyroid hormones are needed organified Tg (with attached T3/T4 molecules) is absorbed via
____ into the thyroid cells
pinocytic vesicles
Once in the blood, 99% of T3 and T4 bind immediately with _____ synthesized by the _____. ______ primary binding protein (80% of T3/T4)
plasma proteins
liver
Thyroxine-binding globulin (TBG) -
Most T4, once absorbed by _____, is converted to T3 by _____
tissues
deiodinases
_____ is metabolically active and is less stable, aka more easily unbound. ____ is more balanced and harder to unbind. What form is the storage form? ____ binds to the receptors with 10-15x more affinity
T3
T4
T4
T3
What would happen to T3/T4 if someone was deficient in TBG, but otherwise metabolically normal? What about to their free T3/T4? TSH/TRH?
total T3/T4 would decrease
Free T3/4 would be normal
TSH/TSH levels would be normal
Estrogen increases the levels of TBG. If someone had high estrogen levels (e.g. pregnancy, contraception), what would happen to their total T3/4? Free T3/T4? and TSH/TRH?
TOTAL T3/4 would increase
Free T3/4: normal
TSH/TRH: normal
What symptoms would you expect to see on a pt with elevated rT3?
hypothyroid s/s
_____ enzyme helps turn T4 into T3?
iodinase
What are some physiologic effects of thyroid on metabolism?
-Growth: especially of skeleton and brain
-Carb metabolism
-Fat metabolism: burns fat, decreases cholesterol, decreases fat stores
-Vitamin metabolism: increases baseline needs for vitamins
-Basal metabolic rate: hyper 60-100% increase. Hypo: up to 50% decrease
-body weight: help to decrease/maintain healthy body weight
What physiologic effects does the thyroid have on the organ systems?
-increased blood flow to tissues
-increased cardiac output
-increased heart rate
-increase heart strength with SLIGHT increase in thyroid hormone
- excitatory/depressive on nerve stimulation
- muscle weakness/sluggishness
-increased breathing rate/depth
- increase hormones secretion from other endocrine glands
What is the effect on the heart of a major increase in thyroid hormone?
weakened heart due to long-term and excessive protein catabolism
**Light periods can indicate _____. Heavy periods can indicate _____
light: can be hyper or hypo
**heavy: HYPO only!
What lab tests make up a thyroid panel?
Thyroid Stimulating Hormone - TSH
Triiodothyronine (total) - T3
Thyroxine (total) - T4
Free Thyroxine Index (unbound) - Free T4 or FT4
What are some interfering factors for TSH lab? What about the time of the day?
severe illness, NSAIDs (very protein bound)
time of the day (TSH is low in the AM and highest in the PM)
a high TSH indicates _____ or _____. _____ T3/4
a low TSH indicates ______. _____ T3/4
hypothyroidism or not enough thyroid meds. Not enough T3/4
primary hyperthyroidism. too much T3/4
primary hyperthyroidism has to due with the _____. Secondary is _____. Tertiary is _____-
thyroid itself
pituitary gland
hypothalamus