thyroid hormone Flashcards
What are the main structural components of the thyroid gland?
follicles lined with follicular cells and filled with colloid
What are the primary hormones produced by the thyroid gland?
T3 T4
What additional hormone does the thyroid gland produce and its function?
calcitonin, which helps regulate calcium levels
10 steps of thyroid hormone synthesis
- TRH release from hypothalamus
- Ani Pit release TSH
- TSH simulates follicular cells to synthesise thyroglobulin
- iodide trapping
- oxidation of iodide
6.iodination of tyrosine amino acids
7.couple DIT and MIT
8.endocytosis of thyroglobulin with T3 and T4 - lysosomal enzymes cleave T3 and T4 out of thyroglobulin
- exocytosis of T3 and T4 into blood plasma
T4 converted to T3 by ?
deiodoniase enzyme
what is the iodine trap
uptake of iodide through iodide-sodium symporter across basolateral membrane
What is the role of T3 in transcriptional regulation?
T3 binds to thyroid receptor to regulate transcription
What is the significance of dimerization in thyroid hormone action?
TR often forms a heterodimer with retinoid X receptor (RXR) to enhance binding to thyroid hormone response elements (TREs).
What are TREs and their function?
specific DNA sequences in target gene promoters that TR binds to regulate transcription.
name a corepressor
HDAC
name a coactivator
HAT
physiological effects of thyroid hormones
accelerated metabolism
development and growth
thyroid hormones effects on autonomic nervous system
increases b-adrenergic receptors and intracellular second messengers
what is hyperthyroidism
excessive production of thyroid hormone
what autoimmune disease can cause hyperthyroidism
graves disease
What are typical symptoms of hyperthyroidism?
Increased heart rate, weight loss, anxiety, heat intolerance, sweating, and tremors
what is hypothyroidism
insufficient production of thyroid hormone
what can cause hypothyroidism
Hashimoto disease
dietary iodine deficiency
defective pituitary function
What are typical symptoms of hypothyroidism?
Fatigue, weight gain, cold intolerance, dry skin, hair loss, and depression
what is goitre
enlarged thyroid gland
effect of thioureylenes
inhibit thyroid hormone synthesis
what is the major method for treating hyperthyroidism
radioiodine
What is the Wolff-Chaikoff effect?
A temporary reduction in thyroid hormone production
name a b-adrenoceptor antagonist
propananolol
what is propranolol used for
block noradrenaline overstimulation of cardiac B1-adrenoceptors
treatment of hypothyroidism
synthetic hormones
What is the importance of MCT8 in the brain?
transports T3 into neuron
which chromosome is MCT8 located on
X
allan-herdon-dudley syndrome is a mutation in
MCT8
