Wk1 Thyroid Phys

Question 1

Describe the hypothalamic pituitary thyroid axis in general terms:

Answer 1

1. tonic release of TRH from hypothalamus
2. TSH released from basophils in anterior pituitary
3. thyroid releases T3 and T4

**T3/4 are feedback inhibitors of TSH and TRH

Question 2

Most important slide…

Answer 2

4

Question 3

TRH receptor type:

Answer 3

Gq –> PLC –> IP3 –> increased Ca –> release TSH

Question 4

TSH receptor type on thyroid follicular cells:

Answer 4

Gs –> increased cAMP –> synthesis and release of T3/4

Question 5

More abundant type of thyroid hormone:

Why?

Answer 5

T4

has longer half life –> loses I- to become T3

Question 6

Three roles of TSH in the production of new thyroid hormones:

Answer 6

1. thyroid peroxidase synthesis
2. thyroglobulin transcription
3. Na/I transporter activity stim

Question 7

Main functions of T3/4?

Answer 7

kinda like catecholamines

necessary for normal growth of most tissues

regulate BMR

increase heat production

increase glucose utilization, uptake, and synth

increased HR and contractility

Question 8

Congenital lack of thyroid hormone in infants:

Answer 8

Cretinism

• profound mental retardation (irreversible)
• short stature
• delayed motor development

Question 9

Anti-TSH receptor antibodies:

Answer 9

Hashimoto’s thyroiditis

Question 10

Hypothyroid sx:

Answer 10

sloth like stuff

COLD intolerance

Question 11

HypERthyroid sx:

Answer 11

road-runner like stuff

Heat intolerance

hyperglycemia

increased catacholamine activity

Question 12

Know what happens to TRH, TSH and TH levels with different defects…

Answer 12

slide 28

Question 13

Production of thyroid stimulating Ig’s:

Answer 13

Grave’s disease

Question 14

What happens to TRH and TSH in Grave’s?

Answer 14

decreased due to increased TH and increased feedback inhibition

Question 15

What causes a goiter?

Answer 15

stimulation of thyroid by either increased TSH in Iodine deficiency (no feed back inhibition from TH)

or

stimulation of thyroid by Ig’s in Grave’s disease

**slides 31-32 !!!!

Question 16

Low TSH = ?

Answer 16

Hyperthyroid

Question 17

High TSH = ?

Answer 17

Hypothyroid

Question 18

T4 analog for hypothyroid tx:

Answer 18

levothyroxine

Question 19

T3 analog for quick hypothyroid tx:

Answer 19

lyothyronine

Question 20

Blocks iodization of tyrosines in colloid to treat hyperthyroid:

Answer 20

Thioamides

• Methimazole
• Propylthiouracil
• Potassium iodide

Question 21

Used to medically ablate thyroid in hyperthyroid:

Answer 21

I-131

**radioactive iodine–> creates hypothyroid sx

**123 is used in imaging