Lecture 60 - Endocrine 2 Flashcards
T/F: thyroid glands are bilobed structures over the trachea
TRUE
what are thyroid hormones composed of
tyrosine and iodine
T4 and T3 differ in
the number of iodine molecules
T/F: T4 is the most abundant thyroid molecule
TRUE
colloid
round-shaped secretory follicles surrounded by cuboidal cells
describe thyroid hormone synthesis in 5 steps
- iodine transported into follicular cell
- iodine diffuses into colloid
- iodine joins with thyroglobulin to form T4/T3
- T3/T4 re-enter cell via endocytosis
- stored in vesicles and enter blood via transport protein
what ion is co-transported into the thyroid gland with iodine
sodium (Na+)
what enzyme influences T4/T3 synthesis
thyroperoxidase
what does methimazole do
inhibits thyroperoxidase activity to lower T3/T4 in blood
what are examples of specific binding proteins
thyroxine
binding globulin
what are examples of non-specific binding proteins
albumin
T/F: there are very small amounts of free thyroid hormone in the plasma
TRUE
Describe the releasing, stimulating, and target hormone in the thyroid
releasing = TRH
stimulating = TSH
target = T4
what will TSH be if T4 is low due to systemic illness
normal to low
what will TSH be if T4 is low due to thyroid disease
high
