week 4 Flashcards
2 hormones from posterior pituiatary and from what neurons
vasopressin (ADH) and oxytocine
magnocellular neurons (PVN and SON nuclei)
PVN vs SON which secretes which hormones
▪ The PVN secretes mostly oxytocin, with a bit of ADH
▪ The SON secretes mostly ADH, with a little oxytocin
vasopressin/ADH function
water regulation and vascoconstrist
oxytocin function
milk letdown reflex and in the augmentation of labour
**smooth muscle contraction via ca2+
2 stimuli for ADH release
- Osmoreceptors (mainly) (osmolarirt)
- baroreceptors (in response to decreased BP and blood volume)
hormones of anterior pituitary
Prolactin, TSH, GH, FSH, LH, ACTH
ADH stimulated by
increased ECF osmolarity
decrease BP/volume
what makes the hormones in the tyroids
follicular cells make t3 and t4
parafollikcular cells in thyroid make
calcitonin, regulate Ca2+
2 things to make thyroid hormoens
tyrosine and iodine
less active and more abundant thyroid homrone
t4
how is t4 made into t3
deiodination
how to iodinate tyrosine to make into thyroid homrones and at which carbons
MIT - 1 iodine at C3
DIT- iodine at C3 and C5
T3 and T4 how many idoines
T3 - MIT + DIT = 3
T4= 2 DIT = 4
where to tyrosines get iodinated
in colloid of thyroid follicles to make t3 and t4
where does tyrosine come from
nitially part of a larger protein known as thyroglobuln
how is iodine in diet absorbed
Na+ I symporter in follicular cells
how does iodine get into the cell
and across apical membrane
NI+ S+ symptorter and then Na+ K+ atpase to
across the apical membrane (the side facing the follicular lumen) by the Cl−/I− exchanger, known as pendrin.
thyroglobulin contains
tyrosyl groups (tyrosine residues) that will be iodinated to form thyroid hormones (T3 and T4).
what enzyme to turn iodide into iodine
thyroid peroxidase (TPO)
TPO needs
DUOX2 generates hydrogen peroxide (H2O2), which is necessary for TPO to oxidize iodide into the iodine radical.
half life of t3 and t4
- T4 has a longer half-life
- T3 has a shorter half-life
carriers for t3 and t4
albumin- low affinity
transthyretin (TTR)
thyroid-binding globulin- high affinity for t4
once t4 enters target tissue how does it become more active form t3
deoiodanse type 1 and 2 (D1 and D2)
D1 vs D2 vs D3 funciton
D1 and D2 turns T4 to T3
D3 turns T4 into reverse T3 (rT3)
cofactor needed for deiodinases (D1, D2, and D3)
selenium
bc selenocysteine residues
rT3 function
compete with T3 receptor and reduce metabolic activity in stress and calorie restrict
hashimotos
cytotoxic T cells
dequervains sub acute thyroididitis causes
viruses
neutrophils and lymphocytes
diffuse non toxic goiter from
iodine defiicney
myxoedema coma
long term hypothyroid PLUS infection
very serious
hypotension –> shock
most common thyrotoxicosis (high levels of thyroid hormone)
graves disease
TSH receptor-stimulating immunoglobulins (TSIs) stimulate the TSH receptor and are not responsive to negative feedback
anti thyroid drugs
propylthioural inhibits TPO and deiodination of T4 to T3
methimazole inhibits TPO
radioactive iodine
for thydoi cancncer
levothyroxine- synthetic t4 for
HYPOthryiod
