Tuesday - Thyroid Phys - Trachte Flashcards Preview

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Flashcards in Tuesday - Thyroid Phys - Trachte Deck (25):
1

What causes a release of TSH

TRH (made in the hypothalamus)

2

Effects of Thyroid hormone

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

3

Negative regulators of TSH

Somatostatin, Dopamine, glucocorticoids

4

Receptor for TRH mechanism

on thyrotrophs of the anterior pituitary

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

5

Receptor for TSH mechanism

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

6

How many Iodine does thyroxine have?

4
T3 = triodothyroxine

7

Difference between T3 and T4

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

8

3 transporters for thyroid homones
how many binding sites?

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

Transthyretin - 2 sites - mostly T4

Albumin - many binding sites - mostly T3

9

How does T4 get broken down?

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

10

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

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

11

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

It's called cretinism - low brain development.

12

What are some things that can cause thyroid deficiency?

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

13

Hypothyroid symptoms in babies

Bone maturation is delayed

cyanosis, jaundice, poor feeding, umbilical hernia

14

Symptoms of low thyroid in adults

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

15

sx of hyper thyroidism

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

(basically increases your metabolic rate)

16

too much thyroid emergency is called

Thyrotoxicosis. can lead to thyroid storm!

17

3 spots in cascade that can lead to hypotyroidism

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.

18

What happens in graves disease

what happens to TSH TRH and TH?

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

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?

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

Hyper -
Graves disease - constant stimulation by antibody

20

Test for Graves Disease

Thyroid Stimulating Immunoglobulin (TSI) test

21

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

T3 and T4

22

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

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

23

What's a thyroid scan good for?

Absolutely nothing!
actually, shows where the iodine is. Can show irregularities

24

3 drugs for treating hyperthyroidism

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

25

What isotope can be used to destroy the thyroid?

131 Iodine