Thyroid Function in Health and Disease

Question 1

What is the function of the thyroid gland?

Answer 1

secrete TH to regulate metabolism and secrete calcitonin to regulate calcium levels

Question 2

What are the major thyroid hormones?

Answer 2

T3 and T4

Question 3

The thyroid gland secretes?

Answer 3

thyroxine and calcitonin

Question 4

Where are T4 and T3 formed in the thyroid gland?

Answer 4

Colloid NOT the follicular thyroid cells

Question 5

What does colloid contain?

Answer 5

Glycoproteins including thyroglobulin where T4 and T3 are made

Question 6

What is the function of C cells? Where are they located?

Answer 6

in interstitial spaces, secrete calcitonin

Question 7

TRH from the hypothalamus is released to the anterior pituitary via the

Answer 7

hypothalamic-hypophyseal portal system

Question 8

TSH is released into

Answer 8

general circulation, travels to thyroid gland

Question 9

Thyroglobulin is produced by

Answer 9

ER and golgi of thyroid follicular cells

Question 10

What is the function of thyroglobulin?

Answer 10

Contains tyrosine that is iodinated by thyroperoxidase to form MIT, DIT, T3, and T4

Question 11

What are the effects of thyroid hormones on homeostasis?

Answer 11

Increased BMR and O2 consumption (calorigenic, thermogenic); modulation of metabolism; sympathomimetic effects (+HR and +CO)

Question 12

What are the effects of thyroid hormones on development?

Answer 12

Growth-promoting in fetal life and after birth (GH and IGF actions); role in nervous system development before and after birth (Px = cretinism)

Question 13

What is the primary diagnostic blood measure in thyroid disorder?

Answer 13

TSH

Question 14

What is the blood profile & presentation of primary hypothyroidism?

Answer 14

-T3 and T4, +TSH = goiter; eg thyroid failure, -dietary iodine

Question 15

What is the blood profile & presentation of secondary hypothyroidism?

Answer 15

-T3 & T4, -TRH and/or -TSH = no goiter; eg hypothalamic or anterior pituitary failure/tumor

Question 16

What are the causes of congenital hypothyroidism?

Answer 16

maternal iodine deficiency, fetal thyroid dysgenesis, inborn errors of TH synthesis, maternal antithyroid Abs, fetal hypopituitary hypothyroidism

Question 17

What are the physiological effects of hypothyroidism?

Answer 17

decreased BMR and O2 consumption, decreased energy, weight gain, cold intolerance, sympathomimetic bradycardia, decreased mentation and reflexes, decreased protein synthesis, puffiness

Question 18

What is the treatment for hypothyroidism?

Answer 18

adequate dietary iodine and replacement T4

Question 19

What is the blood profile & presentation of primary hyperthyroidism?

Answer 19

+T3 and T4, -TSH = goiter; eg Grave’s

Question 20

What immunoglobulins are implicated in Grave’s?

Answer 20

thyroid stimulating immunoglobulin (TSI) from B-lymphocytes, thyroid growth stimulating Ig, TSH-binding inhibitor Ig

Question 21

What is the blood profile & presentation of secondary hyperthyroidism?

Answer 21

+T3 and T4, +TRH and/or TSH = goiter; eg hypothalamic or anterior pituitary excess

Question 22

What is the blood profile and presentation of a hypersecreting thyroid tumor?

Answer 22

+T3 and T4, -TSH = no goiter

Question 23

What are the physiological effects of hyperthyroidism?

Answer 23

increased BMR and O2 consumption, increased appetite, weight loss, muscle weakness, sympathomimetic increases in HR and Co, increased alertness, irritability, hyperexcitability, exopthalmos in Grave’s

Question 24

What is the treatment for hyperthyroidism?

Answer 24

remove thyroid/tumour, thiamines (carbimazole) and B-blockers (symptoms), radioactive iodine

Question 25

What are causes of thyroid overactivity?

Answer 25

toxic adenoma, toxic multinodular goiter, hashimoto's thyroiditis, TSH-secreting pituitary tumors, activating mutations in TSH receptors

Question 26

What are extrathyroidal causes of hyperthyroidsim?

Answer 26

T3 and T4 drugs, ectopic thyroid tissue