L3: The Thyroid Gland

Question 1

What is the largest endocrine gland?

Answer 1

Thyroid gland

Question 2

Thyroid isthmus

Answer 2

Connects the right and left lobe of the thyroid gland

Question 3

Thyroid follicles are functional units that release __

Answer 3

T3 and T4

Question 4

Parafollicular cells (C cells) secrete

Answer 4

calcitonin

Question 5

The thyroid gland is highly ______ with very ____ blood flow

Answer 5

highly, high

Question 6

Follicular cells trap ____ and secrete it with ____ into lumen

Answer 6

iodine, thyroglobulin (TGB)

Question 7

What is the active form of the hormone that the thyroid gland secretes?

Answer 7

T3

Question 8

Draw the hypothalamic - pituitary - thyroid axis (HPT axis)

Question 9

Steps of the TRH and TSH loop (5)

Answer 9

1. Low blood levels of T3 and T4 OR low metabolic rate stimulates the release of
2. TRH, carried by portal veins to anterior pituitary, stimulates release of TSH by thyrotrophs

Question 10

How do T3 and T4 circulate?

Answer 10

They circulate bound to proteins. Free T3 is biologically active

Question 11

What is the primary impact of thyroid hormones?

Answer 11

Basal metabolic rate and thermoregulation

Question 12

What are other physiological effects of thyroid hormones?

Answer 12

Growth
CNS development
Cardiovascular
Metabolism

Question 13

Where are T3 and T4 produced?

Answer 13

Follicular cells

Question 14

What are the majority of steps in the HPT regulated by?

Answer 14

TSH

Question 15

What 4 things fo thyroid hormones need?

Answer 15

iodide, tyrosine, thyroglobulin, thyroglobulin, thyroid peroxidase (TPO)

Question 16

T3/T4 secreted into ___ and bound to ____

Answer 16

RBCs, bind to carrier proteins

Question 17

What are disorders of the thyroid gland?

Answer 17

Hypothyroidism - congenital, endemic, goiter/iodine deficiency, myxedema
Hyperthyroidism

Question 18

Congenital hypothyroidism

Answer 18

Lack of thyroid hormone production during fetal life, infancy, and childhood.
-Lack of functioning thyroid gland

Question 19

Endemic hypothyroidism. Cause and symptoms

Answer 19

Lack of thyroid hormone or lack of iodine
Stunted growth, a slow fusion of bones, intellectual disability

Question 20

What is the treatment for congenital/endemic hypothyroidism?

Answer 20

Iodine therapy and/or thyroxine if early enough before significant growth impairment

Question 21

Endemic goiter

Answer 21

Enlarged thyroid gland from iodine deficiency

Question 22

Idiopathic goiter

Answer 22

Deficiency in
iodine trapping
peroxidase coupling
deiodinases

Question 23

Treatment for goiter

Answer 23

Iodine replacement therapy
Combination therapies target idiopathic goiter
Prenatal vitamins contain iodine

Question 24

Myxedema (untreated hypothyroidism)

Answer 24

Swelling of face and neck interstitial fluid
Can lead to coma and death
It is the lack of thyroid function

Question 25

What is the most common endocrine disorder?

Answer 25

Hypothyroidism (myxedema (untreated hypothyroidsim))

Question 26

How do you treat hypothyroidism?

Answer 26

replace thyroxine

Question 27

Hyperthyroidism

Answer 27

Common: increased thyroid function and suppressed feedback on TSH
Uncommon: localized adenoma (tumour)

Question 28

Treatment of hyperthyroidism

Answer 28

Reduce TH production (thionamides)
Surgical removal of thyroid gland