thyroid hormone Flashcards
drugs and hormones
T3
produced in follicle cells from tyrosine, active form
rT3, is the reverse conformation, also inactive
T4
produced in follicle cells from tyrosine, inactive form.
turned into T3 by tyroperoxidase
thyroperoxidase
turns T4 to T3
catalyses both the iodination reaction and the coupling of tyrosine residues
TG
thyreoglobuline, bounds T4 and T3, in the colloid, preventing spontaneous release
when needed, complex taken up in the follicle and T4 and T3 are released in blood
TBG
determines T3, T4 concentration in blood
increased in pregnancy, neonates, SERM, acute hepatitis and biliary liver cirrhosis
decreases in androgens, glucocorticoid, nephrotic syndrome, terminal kidney failure, chronic lover disease
protirelin
TRH, used in diagnostics
TSH
thyroid stimulating hormone
used in diagnostics
functions;
- iodine uptake
- synthesis and secretion of thyroglubin
- organification
- endocytosis and proteolysis of thyroperoxidase
- secretion of T3 and T4
- growth and vascularization of the thyroid gland
effect thyroid hormone
- activation of carbohydrate, protein and lipid metabolism
- activation of energy consumption and heat protection
- growth and development; brain development
thyroxine, levothyroxine
T4
long acting
hypothyroidism
liothyronine
T3
fast acting
hypothyroidism
thiourea derivatives
carbimazole;
prodrug, thyroperoxidase inhibition
PTU; inhibits T4 > T3 conversion, faster acting
crosses placental barrier
hyperthyroidism
iodine/iodide
inhibition of organification at high concentration
inhibition of hormone release
reduced vascular density
hyperthyroidism
radiotherapy
damage to follicle cells, where production happens
hyperthyroidism
B-blockers
reduces symptoms
increased T4 > rT3 conversion, less active thyroid hormone availble
hyperthyroidism
glucocorticosteroids
immunosuppression
inhibition of T4 > T3 conversion
hyperthyroidism
