Thyroid function

Question 1

features of thyroid gland

Answer 1

shaped like a bow-tie
found just under the thyroid cartilage

Question 2

what are the problems with the thyroid gland

Answer 2

overactive
underactive
goitre (whole thyroid enlarged)
nodules (sections of thyroid enlarged)

Question 3

where are the capillaries located in relation to the thyroid follicles

Answer 3

very close to ensure the hormones enter the bloodstream as endocrine glands are ductless

Question 4

what is T4

Answer 4

the prohormone
can be converted to T3 by deiodinase enzymes

Question 5

what is T3

Answer 5

active hormone

Question 6

how do thyroid hormones circulate in blood

Answer 6

mainly bound to proteins
bound hormone is inactive (99.5%)
active protein is released as needed

Question 7

how is T3 and T4 secreted

Answer 7

thyroid gland secretes T3 and T4 directly into the bloodstream (predominantly T4)
most of T3 is produced by conversion of T4 to T3 in the liver, kidney and muscle (80%)

Question 8

what is the thyroid controlled by

Answer 8

pituitary gland via the thyroid stimulating hormone (TSH), controlled by negative feedback

Question 9

what is the function of thyroid hormone

Answer 9

growth development
thermogenesis in brown adipose tissue
activate mental processes
basal metabolic rate