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
How do thyroid hormones affect basal metabolism
- calorigenic effect - increase oxygen consumption for heat
- enhanced carbohydrate metabolism - overall increased glucose uptake
- enhanced lipolysis - reduce plasma cholesterol concentrations
a hypothyroid dog will present as
overweight, low body temp, high cholesterol
what systemic effects do thyroid hormones have
- neurologic - enhance sympathetic activity
- cardiovascular - support normal HR and BP
- kidney function - supports glomerular filtration
a hyperthyroid cat will present as
ravenous appetite, weight loss, active, fast HR, high BP, “skittish”
