Test # 4 Thyroid hormones Flashcards
(26 cards)
Where is TSH made
pituitary gland in brain
Where is the TSH located
on the plasma membrane
the TRH is made by
the hypothalamus
describe the process of how the actual thyroid hormone is made
- The Hypothalamus is signaled to release TRH onto the pituitary gland.
- This will cause the TSH to be released from the pituitary
- the TSH will then act on the thyroid gland to release T4 which then goes to the tissues
What can feedback to the hypothalamus to decrease the production of TRH if there is too much in the pituitary
TSH - this is called short loop
brain (Pituitary) feeding back to brain (hypothalamus) to stop/decrease the release of TRH which decreases TSH production!
What is the auto feedback mechanism that explains when the target organ (the organ that gets the T4 from the thyroid) gets too much T4 is sends a signal back to the brain (hypothalamus) to decrease the production of TRH?
Long loop - target organ feedback to brain
What disease is when you have low levels of TSH and high levels of T3/T4?
hyperthyroidism - Graves disease
What disease is when you have high levels of TSH and low levels of T3/T4?
hypothyroidism - Hashimoto’s
What kind of receptors do T3/T4 bind to?
Nuclear receptors
they bind in the nucleus of the cells and active the gene expression on the DNA
What is the process called?
if we didn’t have thyroid hormones NOREPI would be useless because. TH promotes gene transcription and some of these are B adrenergic receptor genes - so no hormone = low level of adrenergic receptors. Norepi would not be effective
Premissiveness
What potentates the adrenergic system
TH
What is absolutely required for perinatal brain development - if low levels then it causes____
T3
low levels cause Cretinism (mentally retarded)
What autoimmune disease does it not help to lower TSH levels because there is a formation of antibodies that binds to the TSH receptor and activates them
Graves disease
A drug to treat hyperthyroidism.
It blocks the transport of iodine
found in foods and cigarettes
Jim Jones effect - drank “kool-aid” and killed everyone
Thiocyanate
A drug to treat hyperthyroidism.
It blocks the transport of iodine
10x more active than thiocyanate
Perchlorate
excessive doses (2-3g/day) can cause fatal aplastic anemia
What two drugs tx for hyperthyroid but cross placenta (class D - no pregnant pt) - they can be used but one more than the other\_\_\_\_. Dr. would make sure if it is worth the risk to the fetus
Propylthiuoracil (PTU) and Methimazole
What causes a decrease in thyroxin production at the organification step to stop the production of TH. It decreases the BMR within hours
Iodine
What drug to tx hyperthyroidism leads to partial destruction of the thyroid gland
131I - Radioactive iodine
What drug used to tx hyperthyroidism blocks type 1 deiodinase
propylthiouracil
What drug used to tx hyperthyroidism blocks type 1 and type 2 deiodinase
These drugs also release 75-150mg of iodine which helps inhibit t3/t4 secretion (used as radiology contract dyes)
Sodium ipodate
iopanoic acid
What is a life threatening event which causes exaggerate sympt of hyperthyroidism
(high fever, tachy, n/v, AHF
What is the #1 and #2 treatment plans
and then give what last?
Thyroid Storm
#1: BB to decrease HR #2: antipyretics - to decrease fever Then give PTU to block the conversion of T4 to T3
What autoimmune disorder is caused by a gene defect that does not allow the conversion of T4 to T3 then to TH
Low T4/T3 and high TSH
Hypothyroidism
upper eyelid lowering
fluid accumulation of fluid around neck (not a tumor)
ptosis
goiter
What is it called when you have marked retardation in growth, severe MR, and poor nervous system development in infancy
Cretins
