The Thyroid Gland And Thyroid Disease Flashcards
What shape is the thyroid gland?
Butterfly shaped.
How many lobes does the thyroid gland have?
Two.
Where is the thyroid gland found?
At the front of the base of the neck and either side of the trachea.
What piece of thin tissue joins the lobes of the thyroid gland together?
The isthmus.
How much does the thyroid gland weigh?
Around 30 grams.
How much blood does the thyroid gland receive per minute?
80ml to 120ml.
Where are thyroid hormones synthesized?
Thyrocytes.
Where are thyroid hormones exported to?
The colloid.
Thyroglobulin and glycoprotein contain what kind of residue?
Tyrosine residue.
What ion is actively uptaken in the plasma membrane of thyrocytes?
Iodide.
Iodide is exported to the colloid by what transporter?
Pendrin.
Iodide is incoporated in thyroglobulin by what enzyme?
Thyroid peroxidase.
What four things does thyroglobulin produce?
- T3.
- T4.
- Mono-iodotyrosine (MIT).
- Di-iodotyrosine (DIT).
What is T3 also known as?
Triiodothyronine.
What is T4 also known as?
Thyroxine.
What is the kDa value of thyroglobulin and glycoprotein?
600 kDa.
What does TRH stand for?
Thyrotropin release hormone.
What does TSH stand for?
Thyroid stimulating hormone.
Where is TRH produced?
In the hypothalamus.
What part of the brain does TRH act upon?
The anterior pituitary.
What stimulates the release of TSH?
TRH.
TSH stimulates the thyroid gland to produce what type of hormones?
T3 and T4.
A low blood concentration of T3 and T4 stimulates the release of what?
TRH and TSH.
What does a rise in concentration of unbound T3 and T4 in the blood cause?
The inhibition of TRH and TSH.
What type of tissues deiodinate T4 to T3?
Peripheral tissues (such as the kidney and liver).
Is T3 or T4 the active hormone?
T3.
T4 can be metabolised to a biologically inactive hormone. What is this hormone?
Reverse T3 (rT3).
What are the purpose of thyroid hormones?
They are essential for normal growth and development.
How do thyroid hormones enter cells?
Through different aminoacid transporters.
Thyroid hormones bind specific nuclear receptors dimerizing with what type of receptors?
Retinoid X receptors (RXRs).
Thyroid hormones stimulate gene expression and synthesis of polypeptides, hormones and enzymes. Give an example of a protein produced by thyroid hormones.
Mitochondrial respiration proteins.
Thyroid hormones affect metabolism. What specifically within metabolism is affected?
Basal Metabolic Rate (BMR).
Are thyroid hormones mainly protein bound or protein unbound?
Protein bound.
What type of globulin carries most of T3 and T4?
Thyroxin binding globulin.
Name two proteins that thyroid hormones are bound to within the blood.
Albumin and pre-albumin.
What is the percentage of unbound (free) T4 hormones?
0.02%.
What is the percentage of unbound (free) T3 hormones?
0.2%.
What is the half-life of a T4 hormone?
5 to 7 days.
What is the half-life of a T3 hormone?
1 to 2 days.
Which is more important for the biological effects of hormones - Bound T3 and T4 concentrations or unbound T3 and T4 concentrations?
Unbound.
What is the total plasma concentration of the T3 hormone?
1 to 2.9 nmol/L.
What is the total plasma concentration of the T4 hormone?
60 to 150 nmol/L.
What is the free plasma concentration of the T3 hormone?
3 to 9 pmol/L.
What is the free plasma concentration of the T4 hormone?
9 to 26 pmol/L.
What is the extent of protein binding of T4 in percentage?
99.98%.
What is the extent of protein binding of T3 in percentage?
99.66%.
What are the major pathways of degradation of thyroid hormones?
- Deiodination and metabolism in tissues.
2. They are conjugated in the liver and excreted in bile.
