Thyroid Hormones (Park) Flashcards
what are the physiological effects of thyroid hormones
- growth & development
- metabolic effects
- thermogenesis
- cardiovascular effects
what does T4 look like and its characteristics?
- called thyroxine
- produced more than 10 times
what does T3 look like and its characteristics?
- called triiodothyronine
- more potent than T4
what are the steps of thyroid hormone synthesis?
- iodine in stomach
- transported by NA+I- symporter (NIS)
- goes through gradient through a apical transporter called pendrin
- oxidized by thyroid peroxidase
- iodine-free thyroglobulin transported
- thyroglobulin iodinated by thyroid peroxidase at MIT or DIT position (iodide organification)
- MIT+DIT = T3; DIT+DIT= T4;; coupling is dependent on thyroid peroxidase
- thyroid hormone containing thyroglobulin retrieved back by pinocytosis
- lysosomal exopeptidase cleave T4 or T3 from thyroglobulin and the hormones are released where T4 is converted to T3 by 5’deiodinase
what is iodide organification catalyzed by?
thyroid peroxidase
where is TRH in the axis?
going into anterior pituitary coming from hypothalamus
where is TSH in the axis?
from anterior pituitary going to thyroid hormone
where do thyroid T4 and T3 become produced in axis?
thyroid gland
what is a goiter?
an enlargement of thyroid gland due to a persistent rise of TSH
what is cretinism?
severely stunted physical and mental growth
what is active/inactive in metabolism?
T3 is active, eT3 is inactive, 3,3’-T2 is inactive
what is hypothyroidism ?
deficiency of thyroid hormones
what is a major cause of hypothyroidism?
- Hashimoto’s thyroiditis
–> most common autoimmune disease that destroys the thyroid gland
what is hyperthyroidism/
excessive levels of thyroid hormone
what is a major cause of hyperthyroidism?
graves’ disease
–> most common autoimmune stimulating IgG enlargement of the entire thyroid gland (diffuse toxic goiter)
