Thyroid Hormone (Indra) Flashcards
What are the main thyroid hormones that contain iodine?
T4: thyroxine
T3: triiodothyronine
The thyroid hormone T3 inhibits ________ in the anterior pituitary and inhibits ___________ in the hypothalamus.
On the contrary, what factors stimulate ____________ in the hypothalamus?
thyrotropes, multiple hypothalamic nuclei
multiple hypothalamic nuclei. cold, anxiety, and stress
what are the 4 Glycoprotein hormones?
what type of receptor do they bind to?
luteinizing hormone (LH)
follicle-stimulating hormone (FSH)
thyroid stimulating hormone (TSH)
human chorionic gonadotropin (hCG)
GPCRs
which cell in the thyroid secretes calcitonin?
which secretes T4?
parafollicular cell
follicle cell
The thyroid hormones are synthesized and stored as amino acid residues of _______, a complex glycoprotein made up of two identical subunits, which is discharged into the ______
thyroglobulin, lumen
_______ are actively taken into the thyroid cell, and oxidized to _______, and then released into the lumen.
Iodine attaches to tyrosine, mediated by peroxidase enzymes, forming ____ and _____.
Iodinated tyrosines link together to form ___ and ___
Iodide’s, Iodine
T1 (monoiodotyrosine, or MIT), T2 (diiodotyrosine, or DIT)
T3, T4
Transport and regulation of TH:
T4 and T3 bind to ______________ produced by the liver.
Peripheral tissues convert T4 to T3.
Regulated via negative feedback which can be overcome by ______________
thyroxine-binding globulins (TBGs)
hypothalamic thyrotropin-releasing hormone (TRH)
what is the role of 5’ deiodinase in peripheral tissues?
it converts inactive T4 to active T3
What are important actions of T3:
increased expression of _______ and contractile protein expression in heart.
decreased _______ levels, while increasing _________.
increased _______ and _______ metabolism.
B1-AR
LDL-C, LDLR
lipid, carb
_________ is required for T4/T3 production.
Iodine deficiency causes _______.
iodine deficiency is the most common cause of ______________.
Iodine
hypothyroidism
preventable mental retardation
Uptake of iodide:
Iodine ingested in diet reaches circulation in the form of ______.
Thyroid actively transports it via _____________.
Iodide transport is inhibited by ions such as _______ and _______.
TSH stimulates _____ gene expression and promotes insertion of ____ protein into the membrane.
iodide ion
sodium-iodide symporter (NIS)
thiocyanate, perchlorate
NIS, NIS
overview of hormonal signaling:
T3 binds to _______. T3 induces a conformational change in _____ that promotes its interaction with _______________.
HMEs are recruited to the DNA template to modify histones and:
disrupt histone-DNA interactions and provide a spot for proteins of the pre-initiation complex.
This creates an environment that is permissive for transcription of genes known as ____________.
T3R, T3R, histone-modifying enzymes
T3 target genes
Thyroid hormone has a calorigenic effect, meaning?
they increase metabolism and regulate temperature
Thyroid hormone:
Cardiovascular effects:
increases _____ and contractile protein expression in heart.
______ antags used for hyperthyroidism.
Metabolic effects:
T3 tends to decrease serum ______ levels, hypothyroid pts tend to have elevated _____ levels.
T3 stimulates ____ metabolism and ______ oxidation.
T3 increases _______ levels.
T3 stimulates all forms of ________ metabolism.
Negative feedback:
T3 decreases ____ release.
B1AR
B1AR
cholesterol, lipid
fat, glucose
triglyceride
carb
TSH
what are negative effects of thyroid hormone excess?
positive effects?
Thyroid hormone mimetics are more selective for which THR subtype?
rapid HR, arrhythmia, heart failure, muscle wasting, and bone loss.
reduced LDL-C and fat loss
THR-beta
