Balczon- Thyroid Flashcards
hormones produced from thyroid gland
T3 and T4
calcitonin
unique to thyroid gland; how it stores T3 and T4
extracellularly
thyroid gland extends down from what that takes origin in tongue
thyroglossal duct
blood supply to thyroid
superior and inferior thyroid a.
neural input to thyroid
sympathetics
lymphatic drainage of thyroid
prethyroid and prelaryngeal nodes
basic functional unit of thyroid
follicles
protein that is storage form of T3 and T4 in colloid of follicle
thyroglobulin
cells that produce T3 and T4
follicular
cells that produce calcitonin
parafollicular cells
_____ is stored in secretory granules of parafollicular cells
calcitonin
derived from 4th pharyngeal pouch
parafollicular cells
standard protein producing cell
rER to golgi to secretory granules
parafollicular cells
controlled directly by extracellular calcium
parafollicular cells
secreted when there is elevated Ca2+ in blood and blocks osteoclasts to allow Ca2+ to go from blood to bone and bring levels down
calcitonin
antagonist of parathyroid hormone
calcitonin
steps of thyroid hormone production
- thyroglobulin is made and released into lumen of follicle
- uptake of iodine through Na+/I symporter
- pendrin brings iodine into lumen
- thyroperoxidase takes iodine and attaches it to tyrosine residues on thyroglobulin
- thyroperoxidase couples iodinated phenol rings to another making T3 and T4
- TSH binds and causes endocytosis of thyroglobulin
- lysosomes digest thyroglobulin and release T3 and T4
tyrosine residue with 3 iodines attached
T3
tyrosine with 4 iodines attached
T4
how many month supply of iodinated thyroglobulin
3-4 months
main cause of hypothyroidism in developed countries
Hashimoto’s
main cause of hypothyroidism in underdeveloped countries
iodine deficiency
caused by autoantibodies generated against thyroperoxidase (T3 and T4 not being produced)
Hashimoto’s disease
to diagnose hashimoto’s disease
elevated TSH
low to zero T4
_____% T3 and _____% T4
10% T3
90% T4
____ from hypothalamus is released and goes through hypophyseal portal vein to anterior pituitary and causes release of TSH
TRH (thyrotropin releasing factor)
alpha/beta dimer with the beta portion having specificity for the hormone
TSH
released _____ goes to thyroid gland and binds to TSH receptor
TSH
what 2 things happen when TSH binds to its receptor on follicle of thyroid
- thyroglobulin uptake and digestion (release of T3 and T4)
- activates thyroglobulin synthesis
when T3 and T4 levels are increased what is the feedback inhibition
neg. feedback to TSH and TRH
Gs (cAMP) receptor on basolateral surface of follicular cells
TSH receptor
main cause of hyperthyroidism worldwide
Grave’s disease
caused by autoantibodies that stimulate TSH receptor (too much T3 and T4 produced)
Grave’s disease
to diagnose Grave’s disease
decreased TSH (autoantibodies doing the work without TSH input)
elevated T4
main transporter for T3 and T4 in the blood
thyroxine binding globulin (TBG)
what happens in pregnancy to thyroid
increased in thyroxine binding globulin and increase in total T4 (not free T4)
minor transporter for T3 and T4
albumin
are T3 and T4 active or inactive when bound to thyroxine binding globulin (TBG)
inactive
are T3 and T4 stable or unstable when bound to TBG
stable
2 monocarboxylic transporters that bring T3 and T4 into cells
MCT 8 and 10
thyroid hormone receptor in the cell is a heterodimer and can bind what two things
thyroid hormones (T3 and T4)
retinoic acid
does T3 or T4 bind well to its receptor
T3
_______ convert T4 into T3 to allow it to bind to receptor and induce its effects
deiodinases
prohormone w/ T3 being the active form
T4
deiodinases type I are located at ________ and inactivate T3 and T4 by clipping off iodione
liver and kidney
deiodinases type II are located where
at target cells
what happens if the wrong iodine is clipped off in the liver and kidney
reverse T3 (it will bind to its receptor still but doesn’t activate it)
rT3 (reverse T3) will show up as what
hypothyroidism
stress causes an increase in ______ which will activate deiodinases to clip off wrong iodine and cause rT3 and hypothyroidism
cortisol
type I thyroid hormone receptor is found where and activates genes to increase metabolism
target tissues
type II thyroid hormone receptor is found where and is the part of the mechanism for feedback inhibition
hypothalamus and anterior pituitary
effect of thyroid hormones on metabolism
heat
effect of thyroid hormones on development
nervous system
if deficient in thyroid hormones, what happens to baby
cretinism (mentally deficient and short limbs)
______ hormone assists with IGF-1
thyroid hormone
effect of thyroid hormones on adults
brain health
effect of thyroid hormones on growth
IGF-1 production and release
_____ also plays a role in reproductive health
thyroid hormones
L and R
L: thyroid gland
R: parathyroid gland
basic functional unit of thyroid gland
thyroid follicle
consists of a single layer of follicular cells that surround a colloid-filled cavity
thyroid follicle
main component of the colloid that is the storage form of the thyroid hormones (T3 and T4)
thyroglobulin
located b/t follicles and produce calcitonin
parafollicular cells
inhibits TSH secretion
octreotide
inhibit thyroid peroxidase (thyroperoxidase), thyroid hormone synthesis
sulfonamides
inhibit thyroid hormone release
Iodine and lithium
Glucocorticoids, amiodarone, β-blockers, oral cholecystographic agents (such as sodium ipodate) inhibit ______
T4 to T3 conversion
increases the synthesis of thyroid binding globulin
estrogen
inhibit thyroid hormone reabsorption in gut
Cholestyramine
diagnosis?
hypothyroidism
main treatment of hypothyroidism (synthetic T4 hormone)
Levothyroxine
treatment of myxedema coma (extreme expression of severe hypothyroidism)
IV T4 and T3
diagnosis?
most common cause of this?
hyperthyroidism
Grave’s disease
hyperthyroidism
used to block sympathomimetic effects of hyperthyroidism used in early stages of Grave’s disease
beta blockers (propranolol, atenolol)
to definitively treat Grave’s
total thyroidectomy, followed by thyroid replacement therapy
another way to destroy overactive thyroid cells
radioactive iodine (I131)
Inhibit iodine organification and coupling in the thyroid gland (steps catalyzed by the enzyme thyroidal peroxidase)
PTU and MMI (thionamides)
_____ is drug of choice to treat Grave’s disease longer term
MMI
_____ is used to treat Grave’s disease in pregnant pt in 1st trimester
PTU
____ is used to treat Grave’s disease in pregnant patient in 2nd and 3rd trimester
MMI
the drug of choice to treat Grave’s disease during breastfeeding, as it is not found in mother’s milk
MMI
Life-threatening complication of thyrotoxicosis, often precipitated
by infection, stress, trauma, heart disease, diabetic ketoacidosis
Associated with fever, tachycardia, nausea, agitation, confusion, increase
in catecholamines, increase in blood pressure
Thyroid storm
Propylthiouracil, β-adrenergic antagonists and hydrocortisone used to treat what
Thyroid storm
Propylthiouracil, β-adrenergic antagonists and hydrocortisone all
inhibit _______
T4 to T3 conversion
most common form of thyroid cancer
Papillary thyroid cancer
to treat thyroid cancer
thyroidectomy
radioactive iodine ablation
________carcinoma of the thyroid will not take up iodine and is treated with surgery, external radiation therapy, and chemotherapy including tyrosine kinase inhibitors
medullary
_______is a fully humanized monoclonal antibody to the IGF-1 receptor for the treatment of proptosis, or the outward bulging of the eye, associated with Graves disease
Teprotumumab (Tepezza)
