Tuesday - Thyroid Phys - Trachte

Question 1

What causes a release of TSH

Answer 1

TRH (made in the hypothalamus)

Question 2

Effects of Thyroid hormone

Answer 2

similar to sympathetic stimulation - increase BMR, heat production, glucose utilization, heart rate, contractility

Question 3

Negative regulators of TSH

Answer 3

Somatostatin, Dopamine, glucocorticoids

Question 4

Receptor for TRH mechanism

Answer 4

on thyrotrophs of the anterior pituitary

works through Phosholipase C (g protein Q)–> IP3 –> Ca2+ stores –> secretion of TSH

Question 5

Receptor for TSH mechanism

Answer 5

Gs –> cAMP –> export T3 and T4
(tSh = gS)
also causes thyroglobulin transcription

Question 6

How many Iodine does thyroxine have?

Answer 6

4

T3 = triodothyroxine

Question 7

Difference between T3 and T4

Answer 7

T3 is more active but has a shorter half life (~ 1 day vs. T4 ~ 6 days)

Question 8

3 transporters for thyroid homones

how many binding sites?

Answer 8

Thyroxine binding hormone (TBH) - 1 site. 75%

Transthyretin - 2 sites - mostly T4

Albumin - many binding sites - mostly T3

Question 9

How does T4 get broken down?

Answer 9

Deiodination by deiodinase (outer ring –> T3, inner ring –> reverse T3)
T3 –> T2 (inactive)

Question 10

T3 and T4 go in cell via transporters. What happens next?

Answer 10

act on most cells in body - in the nucleus, bind to Thyroid Hormone Receptor THR –> transcriptional regulation

Question 11

What happens if a baby doesn’t have thyroid hormone?

Answer 11

It’s called cretinism - low brain development.

Question 12

What are some things that can cause thyroid deficiency?

Answer 12

lack of iodine
Hashimotos’s thyroiditis - anti TSH receptor antibodies
radioactive iodine or antithyroid drugs

Question 13

Hypothyroid symptoms in babies

Answer 13

Bone maturation is delayed

cyanosis, jaundice, poor feeding, umbilical hernia

Question 14

Symptoms of low thyroid in adults

Answer 14

lethargy, somnolence, stiffness, cold intolerance, delayed tendon relaxation

Question 15

sx of hyper thyroidism

Answer 15

bone turnover –> hypercalciuria
muscle weaknes/degeneratio/fatigue
heat intolerance
increased gluconeogenesis - bad in diabetics

(basically increases your metabolic rate)

Question 16

too much thyroid emergency is called

Answer 16

Thyrotoxicosis. can lead to thyroid storm!

Question 17

3 spots in cascade that can lead to hypotyroidism

Answer 17

primary - thyroid problem - low TH, high TRH and TSH.
(iodine deficiency, autoimmune (hashimoto), gland destruction)

Secondary - pituitary problem - low TH and TSH but TRH is high

Thyroid hormone resistance - all levels are high.

Question 18

What happens in graves disease

what happens to TSH TRH and TH?

Answer 18

you make antibodies that can mimic TSH.

TH is super high, causes feed back inhibition of TRH and TSH
can cross placenta –>hyperthyroid in baby too

Question 19

Is that a goiter in your throat, or are you just excited to see me?
Why can a goiter be from hyper and hypo thyroid?

Answer 19

Hypo -
Idodine deficiency –> no TH –> more TRH –> stimulates thyroid.

Hyper -
Graves disease - constant stimulation by antibody

Question 20

Test for Graves Disease

Answer 20

Thyroid Stimulating Immunoglobulin (TSI) test

Question 21

If TSH is high or low, next test to do is?

Answer 21

T3 and T4

Question 22

Radioactive iodine is uptaken a lot, what might that mean?

Answer 22

Grave disease, because you’re taking up a lot of iodine to be used for TH

Question 23

What’s a thyroid scan good for?

Answer 23

Absolutely nothing!

actually, shows where the iodine is. Can show irregularities

Question 24

3 drugs for treating hyperthyroidism

Answer 24

Methimazole - inhibits peroxidase
Propylthiouracil
 - inhibit thyroid peroxidase and de-iodinase
Potassium Iodinde
 - don't know why it works

Question 25

What isotope can be used to destroy the thyroid?

Answer 25

131 Iodine