thyroid gland

Question 1

what is the blood supply of the thyroid ?

Answer 1

superior thyroid artery branch of the external carotid for the upper part
inferior thyroid artery branch of the thyrocervical trunk for the bottom part

Question 2

what is the connection between the thyroid and the tongue ?

Answer 2

the thyroglossal duct

Question 3

what is the origin of the thyroid ?

Answer 3

the remanent of the thyroglossal duct which is the endoderm of the foramen cecum

Question 4

what is the pathology of a thyroglossal duct cyst ?

Answer 4

persistence of the thyroglossal duct

Question 5

what is the presentation of the thyroglossal duct cyst ?

Answer 5

it is a midline neck mass that is usually painless and moves up and down with swallowing or tongue protrusion

Question 6

what is the most common location for ectopic thyroid tissue ?

Answer 6

base of the tongue

Question 7

what is the presentation of ectopic thyroid ?

Answer 7

presents as a mass in the tongue
detected during puberty or during pregnancy
may be associated with hypothyroidism
increased TSH

Question 8

what are thyroid follicular cells derived from ?

Answer 8

derived from endoderm

Question 9

where do thyroid parafollicular cells arise from ?

Answer 9

arise form 4th pharyngealpouch

Question 10

which cells of the thyroid are responsible for making the hormones ?

Answer 10

the follicular cells

Question 11

what are the thyroid hormones and what are they made from ?

Answer 11

T3 T4 and TSh
made from tyrosine and iodine

Question 12

what are the changes that iodine must go through to be taken by our body ?

Answer 12

uptake by follicular cells first
then oxidation
then organification

Question 13

how does the iodine uptake by follicular cells happen ?

Answer 13

NIS - sodium iodine symporter , brings in iodine and sodium into the salt

Question 14

what are the inhibitors of the NIS symporter?

Answer 14

perchlorate
pertechnetate

Question 15

what is the enzyme responsible for the oxidation of iodine ?

Answer 15

thyroid peroxidase
from iodide to I2

Question 16

what antibody is commonly seen in autoimmune thyroid disease ?

Answer 16

Anti TPO

Question 17

what converts T4 into T3 ?

Answer 17

5 deiodinase ( peripheral conversion)

Question 18

what drugs are used to inhibit TPO enzyme?

Answer 18

Methimazole
PTU

Question 19

beta blocker and blocks 5 deiodenase ?

Answer 19

propanolol

Question 20

what is the wolff chaikoff effect ?

Answer 20

prevention of the occurence of hyperthyroidism due to an excess in iodine consumption
where the organification process is inhibited by an excess of the iodide levels

Question 21

what cardiac drug can cause hypothyroidism ?

Answer 21

amiodarone
via excess iodine
via the wolff chaikoff effect
mimics T4 and inhibits deiodinase enzyme

Question 22

what are the thyroid hormone levels associated with the consumption of amiodarone ?

Answer 22

a decrease in T3
and a small rise in TSH

Question 23

what is the carrier protein for T4 ?

Answer 23

TBG
thyroxine binding globulin

Question 24

what is the result of less TBG in the plasma ?

Answer 24

less available T4/T3 to be used in tissues

Question 25

what are the factors that can effect the levels of TBG ?

Answer 25

estrogen rises the levels of TBG liver failure lowers the TBG levels

Question 26

how do thyroid hormones exert their effect on cells ?

Answer 26

through thyroid hormone receptors

Question 27

what is the main effect of thyroid hormones ?

Answer 27

major regulator of metabolic activity and growth

Question 28

what are the metabolic effects in hypothyroid patients vs in hyperthyroid patients ?

Answer 28

hypothyroid : inc cholesterol hyperthyroid : hyperglycemia, weight loss

Question 29

what are the cardiac effects of thyroid hormones ?

Answer 29

increased cardiac contractility - hence the tachycardia increase the number of B1 receptors

Question 30

what is the effect of thyroid hormones on the CNS and bone effects ?

Answer 30

childhood hypothyroidism - cretinism

Question 31

what is the most common cause of treatable mental retardation ?

Answer 31

cretinism

Question 32

what is the thyroid hormone receptor regulator ?

Answer 32

TSH which is released by the anterior pitutary

Question 33

what is the method of activation in which TSH works by ?

Answer 33

activated the cAMP/PKA 2nd messenger system

Question 34

what is the order in which thyroid hormones are released from ?

Answer 34

TRH from the hypothalamus then TSH from the anterior pituitary then binds to TSH receptors on the thyroid gland

Question 35

what is the effect of activation of PKA ?

Answer 35

stimulates the uptake of iodide ions and promotes the organification of Iodide

Question 36

what is the effect of pregnancy on thyroid hormone production ?

Answer 36

due to the high levels of estrogen , more T3 and T4 hCG stimulates the thyroid raises T$ and lowers the TSH

Question 37

what other hormone is produced by the thyroid ?

Answer 37

calcitonin which is made by parafollicular cells also called C cells

Question 38

what is the physiologic effect of calcitonin ?

Answer 38

lowers serum calcium used for hypercalcemia patients