Thyroid System

Question 1

Thyroid Gland

Answer 1

Produces a mixture of T3 and T4 (thyroxine) that control metabolic rate (MR)

Question 2

T3

Answer 2

Active form of thyroxine

Question 3

T4

Answer 3

A pro-hormone and is given for thyroid hormone replacement and is the inactive form

Question 4

How do hormone levels and MR change in response to winter vs summer?

Answer 4

Increase in winter and decrease in the summer (also decrease with starvation and dieting)

Question 5

Dietary Iodide

Answer 5

T3 and T4 require this for synthesis

Question 6

How long can Ts last without Iodide?

Answer 6

The iodide stored in the gland help them to last up to two months without it

Question 7

Goiter

Answer 7

Caused by no Ts and no negative feedback, causes hi TSH which stimulates gland growth

Question 8

Tumors

Answer 8

Tumors that overproduce a hormone can occur at any stage, tumors don’t respond to negative feedback

Question 9

Hyperthyroidism

Answer 9

Most common form is Grave’s Disease, autoimmune, except antibodies stimulate gland to grow and secrete Ts

Question 10

Exopthalmus

Answer 10

Hyperthyroidism, gland is often 2-3 times the normal size and eyes can protrude

Question 11

Signs of Hyperthyroidism or Grave’s Disease

Answer 11

Weight loss, heat intolerance, muscle weakness, nervousness, can’t sleep, fatigued

Question 12

Hypothyroidism

Answer 12

Most common form is Hashimoto’s Disease, autoimmune attack on the gland

Question 13

Signs of Hypothyroidism or Hashimoto’s Disease

Answer 13

Fatigue, sluggishness, husky voice, puffy appearance, weight gain

Question 14

Cretinism

Answer 14

Retardation because nervous system doesn’t develop right without Ts

Question 15

What can cause Cretinism?

Answer 15

Congenital hypothyroidism and failure of gland to develop or faulty enzyme in T synthesis pathway