Wk1 Thyroid Phys Flashcards
Describe the hypothalamic pituitary thyroid axis in general terms:
- tonic release of TRH from hypothalamus
- TSH released from basophils in anterior pituitary
- thyroid releases T3 and T4
**T3/4 are feedback inhibitors of TSH and TRH
Most important slide…
4
TRH receptor type:
Gq –> PLC –> IP3 –> increased Ca –> release TSH
TSH receptor type on thyroid follicular cells:
Gs –> increased cAMP –> synthesis and release of T3/4
More abundant type of thyroid hormone:
Why?
T4
has longer half life –> loses I- to become T3
Three roles of TSH in the production of new thyroid hormones:
- thyroid peroxidase synthesis
- thyroglobulin transcription
- Na/I transporter activity stim
Main functions of T3/4?
kinda like catecholamines
necessary for normal growth of most tissues
regulate BMR
increase heat production
increase glucose utilization, uptake, and synth
increased HR and contractility
Congenital lack of thyroid hormone in infants:
Cretinism
- profound mental retardation (irreversible)
- short stature
- delayed motor development
Anti-TSH receptor antibodies:
Hashimoto’s thyroiditis
Hypothyroid sx:
sloth like stuff
COLD intolerance
HypERthyroid sx:
road-runner like stuff
Heat intolerance
hyperglycemia
increased catacholamine activity
Know what happens to TRH, TSH and TH levels with different defects…
slide 28
Production of thyroid stimulating Ig’s:
Grave’s disease
What happens to TRH and TSH in Grave’s?
decreased due to increased TH and increased feedback inhibition
What causes a goiter?
stimulation of thyroid by either increased TSH in Iodine deficiency (no feed back inhibition from TH)
or
stimulation of thyroid by Ig’s in Grave’s disease
**slides 31-32 !!!!
