lecture 23

Question 1

Where are thyroid hormones synthesised

Answer 1

Thyroid gland - located between larynx and trachea

Question 2

important sections of thyroid gland

Answer 2

thyroid follicle - these are the cells which are important for secretion
thyroid colloid - this is where thyroid hormone precursors are stored

Question 3

What are the 2 key elements of thyroid synthesis

Answer 3

tyrosine and iodine

Question 4

which thyroid hormone is more active

Answer 4

T3

Question 5

how is most circulating T3 formed

Answer 5

by deiodination of T4

Question 6

why does thyroid hormon ehave to bind to proteins ( TBG and TTR)

Answer 6

because it isnt water soluble

Question 7

normal thyroid hormone secretion

Answer 7

euthyroid state

Question 8

low thyroid secretion

Answer 8

hypothyroid ( myxoedema)

Question 9

excessive thyroid hormone secretion

Answer 9

hyperthyroid ( thyrotoxicosis)

Question 10

What is the function of Thyroid stimulating hormone (TSH)

Answer 10

• stimulates T3 and T4 production
• increases protein synthesis in follicular cells , increasing dna replication and cell division
• increases rough ER required for protein synthesis

Question 11

what happens if too much TSH

Answer 11

thyroid undergos hypertrophy and can result in goitre

Question 12

what state does goitres form in

Answer 12

hypo/hyper and euthyroidism

Question 13

What is a big trigger to look at thyroid levels

Answer 13

weight changes

Question 14

Increased thyroid increases

Answer 14

metabolism, heat prduction, response to sympathetic output

Question 15

What is the most ectreme result of iodine deficiency

Answer 15

cretinism

Question 16

How to test thyroid function

Answer 16

TSH test (norm 0.27-4.2)
Free T4 test (norm 12-22)
Free T3 test (norm 3.1-6.8)

Question 17

hyperthyroidism TSH and T4 levels

Answer 17

TSH low , T4 high

Question 18

primary hypothyroidism TSH and T4 levels

Answer 18

TSH high
T4 low

Question 19

secondary hypothyroidism TSH and T4 levels

Answer 19

TSH low
T4 low

Question 20

hypothyroidism symptoms

Answer 20

cold intolerance, weight gain, bradycardia, tired, constipated, forgetful

Question 21

possible cause of primary hypothyroidism

Answer 21

inadequate iodine consumption

Question 22

Who is more likely to get hypothyroidism

Answer 22

women

Question 23

what is the most common cause of hypothyroidism

Answer 23

hashimotos thyroiditis

Question 24

primary hypothyroidism treatment

Answer 24

levothyroxine ( a synthetic T4)

Question 25

pregnancy effect on levothyroxine dose

Answer 25

needs to be monitored monthly and require 50-100% dose increase

Question 26

levothyroxine se

Answer 26

hair loss for first few months, headaches, insomnia, nervousness, fever, tachycardic, weight changes

Question 27

what is liothyronine

Answer 27

synthetic T3

Question 28

what are the risks of T3 therapy on hypothyroidism

Answer 28

may cause bone and heart issues (osteoporosis and arrhythmia

Question 29

What drug is more potent to treat hypothyroidism

Answer 29

Liothyronine is 5 times more potent than T4 - max efect reached in 24 hrs vs 20 days in levothyroxine and Liothyronine passes off faster with a lower half life

Question 30

What type of hypothyroidism is uncommon

Answer 30

secondary hypothyroidism

Question 31

what happens in secondary hypothyroidism

Answer 31

pituitary gland doesnt produce TSH so T3,T4 and TSH are all below normal levels

Question 32

what is the end result of untreated hypothyoridism

Answer 32

Myxodema coma

Question 33

What are the signs of Myxodema coma

Answer 33

extreme weakness-> loss of consciousness , extreme hypothermia, seizures

Question 34

What are drugs which effect the thyroid function

Answer 34

corticosteroids - decrease TRH and TSH production Lithium - inhibits release of hormones and interferes with deiodination amiodarone - contains iodine cholestyramine - reduces absorption by reducing blood cholesterol

Question 35

hyperthyroidism symptoms

Answer 35

heatr intolerance, palpitations, weight loss, restlessness, fatigue, sweating

Question 36

What causes Hyperthyroidism

Answer 36

Production of excess T4

Question 37

bloods would show what in hyperthyroidism

Answer 37

Low TSH, high T4

Question 38

what is graves disease

Answer 38

the most common cause of hyperthyroidism - goiters or exophthalmos

Question 39

What causes graves disease

Answer 39

Thyroid stimulating immunoglobulin, this activates TSH receptor which increases thyroid hormone secretion

Question 40

Treatment of hyperthyroidism

Answer 40

some drugs, Surgery or radioactive iodine capsules which emit gamma and beta radiation - usually lasts 3 months but can last up to 6

Question 41

What are some antithyroid drugs

Answer 41

thioamides like carbimazole or propylthiouracil which inhibit thyroid peroxidase ( stops iodination ). Propylthiouracil also inhibits peripheral deiodination - this has a slow onset