The thyroid gland; control of secretion

Question 1

where does thyroid tissue arise during development

Answer 1

foramen caecum

Question 2

what connects the developing thyroid to the tongue

Answer 2

thyroglossal duct

Question 3

what cells are found in the thyroid

Answer 3

follicular cells and parafollicular cells

Question 4

what hormone does the thyroid produce apart from T3 and 4

Answer 4

calcitonin (calcium homeostasis)

Question 5

describe the triggers of thyroid hormone release

Answer 5

Thyrotropin releasing hormone (hypothalamus)

thyroid stimulating hormone (anterior pituritary)

Question 6

what is the most common cause of hypothyroidism

Answer 6

iodine

Question 7

what two chemicals make thyroid hormone

Answer 7

iodine and tyrosine

Question 8

describe the formation of thyroid hormones

Answer 8

addition of successive iodide ions to thyroglobulin (precursor)

Question 9

describe the regulation of thyroid hormones

Answer 9

negative feedback loop

increased by cold temps
decreased by dopamine and somatostatin

Question 10

what is the function of calcitonin

Answer 10

parafollicular cells produce calcitonin in response to high blood calcium
calcitonin decreases the release of calcium from bone

Question 11

what is the function of parathyroid hormone

Answer 11

increases blood calcium by stimulating bone break down

Question 12

what part of the hypothalamus secretes TRH

Answer 12

arcuate nucleus and median eminence

Question 13

where is TRH released

Answer 13

anterior pituitary

Question 14

what is the other name for T4

Answer 14

thyroxine

it is a prohormone of T3

Question 15

what is the other name for T3

Answer 15

triiodothyronine

Question 16

describe synthesis and secretion of T3 and 4

Answer 16

TSH stimulates sodium iodide co transporter resulting in iodine trapping
iodide leaves the cell and enters the lumen
the follicular cell secretes thyroglobulin
TSH stimulates iodination of thyroglobulin in the lumen and conjugates iodinated tyrosines
TSH stimulates endocytosis of thyroglobulin
thyroglobulin undergoes proteolysis forming t4 and 3
TSH stimulate secretion into the circulation

Question 17

where is TSH made

Answer 17

anterior pituitary gland

Question 18

where is TSH made

Answer 18

anterior pituitary gland

Question 19

what hormone causes hyperplasia of the thyroid gland

Answer 19

TSH

Question 20

What molecule are thyroid hormones bound to in the circulation

Answer 20

thyroxin binding globulin

Question 21

what is the function of 5’ 3’ monoiodinase

Answer 21

converts T4 to T3

Question 22

what is the function of TBG and other binding proteins

Answer 22

buffers free T3 and T4 in the blood

Question 23

what are the functions of thyroid hormones

Answer 23

increase glucose uptake from the GI tract
increase glucose utilization
increase liver glycogenolysis and gluconeogenesis
increased lipolysis
increase oxidation of free fatty acid

permissive action for other hormones essential for normal development and function

Question 24

what are the effects of fetal hypothyroidism

Answer 24

neuronal hypoplasia
delayed myelination
mental retardation

Question 25

what are goitrogens

Answer 25

excess iodine, thiocyanate or perchlorate causes excess TSH secretion so hypertrophy of thyroid

Question 26

what is the effect of pituitary tumours on the thyroid

Answer 26

may cause over or underproduction of TSH

Question 27

what is Grave’s disease

Answer 27

Long acting thyroid stimulator - autoimmune stimulation of the thyroid

Question 28

what is hashimoto’s disease

Answer 28

autoimmune destruction of the thyroid