Endo week 5 Flashcards
3 enzymes used in thyroid hormone biosynthesis
3 enzymes used in thyroid hormone biosynthesis?
Peroxidase:
- for oxidation of I- to I2
- for organification of I2
- for coupling reaction of MIT, DIT, T3, T4
Proteases:
hydrolysis of T3 & T4 from thyroglobulin
Deiodinase Tyrosine:
deiodination of residual MIT & DIT, recycling of I-
what is an endemic goitre?
what is an endemic goitre?
insufficient dietary iodine, increases size of thyroid gland.
what are the 3 transport proteins for thyroid hormone?
which thyroid hormone has a greater affinity to bind to TBG?
what are the transport proteins for thyroid hormone?
70% is thyroxine-binding globulin
some thyroxine binding prealbumin
some albumin
which thyroid hormone has a greater affinity?
T4
in liver failure TBG levels increase or decrease?
in pregnancy TBG levels increase or decrease?
in liver failure TBG levels increase or decrease?
Answer: Decrease
in pregnancy TBG levels increase or decrease?
Answer: Increase
Thyroid hormone can be stored for?
A. 1-2 months
B. 2-3 months
C. 3-4 months
D. 2 weeks
Thyroid hormone can be stored for?
Answer: B. 2-3 months
which thyroid hormone is more biologically active?
which thyroid hormone has a longer plasma half-life?
which thyroid hormone is more biologically active?
Answer: T3
which thyroid hormone has a longer plasma half-life?
Answer: T4
T3 has high affinity for intracellular thyroid hormone receptor?
A. True
B. False
T3 has high affinity for intracellular thyroid hormone receptor?
Answer: True
where are thyroid hormone receptors located?
where are thyroid hormone receptors located?
Answer: inside the nuclei
If patient has hypothyroidism, what happens to plasma cholesterol levels in blood?
If patient has hypothyroidism, what happens to plasma cholesterol levels in blood?
Answer: Cholesterol increases, accumulation in blood vessel wall
what is graves’ disease?
what is graves’ disease?
excessive stimulation of the TSH receptor by an autoantibody
T3 has negative feedback on thyrotropes by repressing 2 things?
T3 has negative feedback on hypothalamus by inhibiting?
T3 has negative feedback on thyrotropes by repressing 2 things?
- TSH expression
- thyrotrope sensitivity to TRH
T3 has negative feedback on hypothalamus by inhibiting?
Answer: TRH production and secretion
causes for hyperthyroidism?
causes for hyperthyroidism?
Answer:
- Toxic adenoma
- Pituitary tumour secreting more TSH
- Ectopic tissue
- Grave’s disease (autoimmune antibodies bind to TSH receptors and stimulate TH release)
causes for hypothyroidism?
causes for hypothyroidism?
Answer:
- iodine deficiency
- antithyroid antibodies (Hashimoto thyroiditis)
- hypopituitarism
- Foetal thyroid dysgenesis
