Thyrotoxicosis Flashcards
The thyroid is located below which important structure in the trachea and either side of what cartilaginous area?
1 - pharynx
2 - tongue
3 - vocal cords
4 - larynx
4 - larynx
- cricoid cartilage
What is the main function of the thyroid gland?
1 - regulate insulin sensitivity
2 - regulate basal metabolic rate
3 - regulate Ca2+ levels
4 - regulate cortisol release
2 - regulate basal metabolic rate
What important chemical that must be consumed in the diet is required for thyroid hormone production?
1 - vitamin K
2 - B12
3 - iodine
4 - iron
3 - iodine
- recommended 150ug/day
- contained within seafood, dairy products, seaweed, iodized salt, prunes, potatoes, lima beans
The thyroid is not a uniform structure, rather it is composed of follicles. Each follicle is composed of which type of epithelial cells?
1 - cuboidal epithelial cells
2 - squamous epithelial cells
3 - columnar epithelial cells
4 - transitional epithelial cells
1 - cuboidal epithelial cells
The thyroid is not a uniform structure, rather it is composed of follicles. Each follicle is composed of cuboidal epithelial cells. What is the name of the area contained within the follicles that is surrounded by cuboidal epithelial cells?
1 - thyroglubulin
2 - colloid
3 - follicle
4 - calcitonin
2 - colloid
The thyroid contains C cells. What do these cells secrete?
1 - Ca2+
2 - parathyroid hormone
3 - thyroglobulin
4 - calcitonin
4 - calcitonin
- regulate plasma calcium levels
Label the cross section of the thyroid gland using the labels below:
follicle
RBCs
capillary
C cells
colloid
cuboidal epithelial cells
1 - follicle
2 - capillary
3 - C cell
4 - cuboidal epithelial cell
5 - RBCs
6 - colloid
In development the thyroid gland develops from the floor of what?
1 - pharynx
2 - tongue
3 - vocal cords
4 - larynx
1 - pharynx
- near the root of the tongue
Colloid is a substance that is contained within the follicles of the thyroid gland. What is the colloid substance composed of?
1 - Ca2+
2 - parathyroid hormone
3 - thyroglobulin
4 - calcitonin
- thyroglobulin
- thyroglobulin is a large (660 kDa) tyrosine rich dimeric glycoprotein
Colloid is a substance that is contained within the follicles of the thyroid gland. The colloid substance is rich in thyroglobulin, a large (660 kDa) tyrosine rich dimeric glycoprotein. The thyroglobulin is produced by which 2 organelles of the follicular cuboidal epithelial cells?
1 - rough endoplasmic reticulum
2 - smooth endoplasmic reticulum
3 - golgi apperatus
4 - perioxome
1 - rough endoplasmic reticulum
3 - golgi apperatus
- golgi
Thyroglobulin, the precursor for thyroid hormones and contains between 10-20 thyroid molecules that can be used to form thyroxine (T4) and triiodothyronine (T3). Iodine is bound to tyrosine residues of the thyroglobulin. Iodine and tyrosine are then cleaved from the thyroglobulin forming T1 and T2. T1 and T2 can the be combined to create T4 and T3. The thyroid secretes thyroxine (T4) and triiodothyronine (T3). What % of T3 and T4 are secreted?
- triiodothyronine (T3) =7%
- thyroxine (T4) = 93%
Triiodothyronine (T3) and thyroxine (T4) referred to as T3 and T4, why are they referred to as T3 and T4?
1 - number of thyroglobulin molecules
2 - refers to activity on metabolism
3 - refers to number of tyrosine
4 - refers to number of iodine
4 - refers to number of iodine
- T3 = 3 iodine molecules
- T4 = 4 iodine molecules
Triiodothyronine (T3) and thyroxine (T4) are referred to as T3 and T4 because the T relates t tyrosine amino acid and the number relates to the number of iodine molecules bound to the tyrosine (T3 = 3 iodine molecules and T4 = 4 iodine molecules). Does T3 or T4 have a longer half life?
- T4 has a longer half life
- T4 can be converted into T3 within cells
What are the 2 major extra-thyroidal organs that convert Thyroxine (T4) into triiodothyronine (T3)?
1 - heart
2 - skeletal muscle
3 - liver
4 - kidneys
3 - liver
4 - kidneys
2 - kidney
The 2 major extra-thyroidal organs that convert Thyroxine (T4) into triiodothyronine (T3) are the liver and the kidneys. What enzyme is response for converting T4 into T3?
1 - iodothyronine de-iodinases
2 - HMG-CoA synthase
3 - HMG-CoA reductase
4 - lipase
1 - iodothyronine de-iodinases
- can convert to active or inactive T3
The 2 major extra-thyroidal organs that convert Thyroxine (T4) into triiodothyronine (T3) are the liver and the kidneys. Iodothyronine de-iodinases can convert T4 into the active T3. There are 3 types of de-iodinases:
- Type I and II = catalyses T4 to biological active T3
- Type III = catalyses T4 into reverse (inactive) T3.
Where is type I Iodothyronine de-iodinases most commonly found?
1 - liver
2 - kidneys
3 - thyroid
4 - all of the above
4 - all of the above
- type 2 (D2) = muscle, brain, pituitary, skin and placenta
The 2 major extra-thyroidal organs that convert Thyroxine (T4) into triiodothyronine (T3) are the liver and the kidneys. Iodothyronine de-iodinases can convert T4 into the active T3. There are 3 types of de-iodinases:
- Type I and II = catalyses T4 to biological active T3
- Type III = catalyses T4 into reverse (inactive) T3.
Where is type II Iodothyronine de-iodinases most commonly found?
1 - pituitary
2 - muscle
3 - CNS
4 - thyroid
5 - placenta
6 - all of the above
6 - all of the above
- type 2 (D2) = muscle, brain, pituitary, skin and placenta
The 2 major extra-thyroidal organs that convert Thyroxine (T4) into triiodothyronine (T3) are the liver and the kidneys. Iodothyronine de-iodinases can convert T4 into the active T3. There are 3 types of de-iodinases:
- Type I and II = catalyses T4 to biological active T3
- Type III = catalyses T4 into reverse (inactive) T3.
Where is type III Iodothyronine de-iodinases most commonly found?
1 - CNS
2 - placenta
3 - all of the above
3 - all of the above
- type 2 (D2) = muscle, brain, pituitary, skin and placenta
Re-organise how is thyroglobulin created in the cuboidal epithelial cells and secreted into the colloid?
1 - thyroglobulin is synthesised in rough endoplasmic reticulum
2 - endocytosis secretes vacuoles into colloid where iodine is added to the tyrosine molecules of the thyroglobulin
3 - thyroglobulin and peroxidase packed into vacuoles
4 - amino acid (tyrosine) and iodide are taken up by thyroid gland from blood
5 - sugars added to thyroglobulin in golgi
4 - amino acid (tyrosine) and iodide are taken up by thyroid gland from blood
1 - thyroglobulin is synthesised in rough endoplasmic reticulum
5 - sugars added to thyroglobulin in golgi
3 - thyroglobulin and peroxidase packed into vacuoles
2 - endocytosis secretes vacuoles into colloid where iodine is added to the tyrosine molecules of the thyroglobulin
Reorganise how thyroglobulin is converted into thyroxine (T4) and triiodothyronine (T3) and secreted into the blood?
1 - colloid droplets of thyroglobulin merge with lysosomes
2 - T3 and T4 are then secreted into the blood
3 - thyroglobulin broken down and endocytosed into the the cuboidal epithelial cells
4 - lysosomes proteolytic enzymes breakdown thyroglobulin into T3 and T4
3 - thyroglobulin broken down and endocytosed into the the cuboidal epithelial cells
1 - colloid droplets of thyroglobulin merge with lysosomes
4 - lysosomes proteolytic enzymes breakdown thyroglobulin into T3 and T4
2 - T3 and T4 are then secreted into the blood
What transporter is present on the basolateral membrane (closest to the blood vessels) of the thyroid follicular cells that allows iodide to enter the thyroid follicular cells?
1 - Na+/iodide symtransporter
2 - Na+/K+ ATPase
3 - pendrin
4 - thyroid peroxidase
1 - Na+/iodide symtransporter
- iodide molecule crosses with 2 Na+ molecules
- N+ moves down concentration gradient
- iodide- moves against concentration gradient as lots of iodide already in the cell
What is present on the apical membrane (facing the colloid) thyroid follicular cells that is initially involved in transporting iodide into the colloid and the oxidation of iodide into something else?
1 - Na+/iodide symtransporter
2 - Na+/K+ ATPase
3 - pendrin
4 - thyroid peroxidase
3 - pendrin an anion (negative charge ion) exchanged
- exchanges iodide- for Cl-
- involved in oxidising iodide into iodine in the colloid
Pendrin is present on the apical membrane (facing the colloid) of the thyroid follicular cells and is initially involved in oxidation of iodide into iodine. What other enzyme is involved in the oxidation of iodide to iodine and the binding of iodine to thyroglobulin?
1 - iodothyropsine de-ionidase
2 - thyroid peroxidase
3 - peroxidase
4 - lipase
2 - thyroid peroxidase
facilitates the formation of T3 and T4 through combinations of monoiodotyrosine (MIT) and diiodotyrosine (DIT)