Endo 4 - Hypothyroid Disorders

Question 1

Which hormone switches on follicular cells in the thyroid gland?

Answer 1

TSH

Question 2

What is Thyroxine important for?

Answer 2

keeping BMR high

Question 3

What are the white bits seen near the thyroid on a scan?

Answer 3

Colloid, white bits where thyroxine is being released

Question 4

What are some of the effects of hypothyroidism?

Answer 4

• reduced BMR
• cold intolerance
• bradycardia
• speech slows down
• tongue gets thick
• weight gain
• loss of appetite
• lethargy
• depression
• constipation

Question 5

Will TSH be high or low?

Answer 5

High

Question 6

What hormones are secreted by the thyroid?

Answer 6

T3 and T4

Question 7

Is T3 or T4 the prohormone?

Answer 7

T4

Question 8

Which hormone is the pharmacologically active one?

Answer 8

T3

Question 9

Which form is mainly released by the thyroid?

Answer 9

T4

Question 10

What converts t4 to t3?

Answer 10

Deiodinase

Question 11

Describe the mechanism of action of thyroxine?

Answer 11

• Thyroxine enters the target cell
• t4 gets converted to t3 via deiodinase
• T3 binds to thyroid hormone receptor in the nucleus
• heterodimerises with a retinoid X receptor
• this then binds to the thyroid response element which causes changes in gene expression

Question 12

What is the T4 replacement drug?

Answer 12

Levothyroxine Sodium

Question 13

What is the t3 replacement drug?

Answer 13

Liothyronine Sodium

Question 14

What is thyroxine replacement used for?

Answer 14

Autoimmune Primary Hypothyroidism

Iatrogenic primary hypothyroidism

Question 15

How often is the drug taken?

Answer 15

Daily

Question 16

What do you use to guide dosage?

Answer 16

Want to suppress TSH to within reference range

Question 17

Describe the levels of TSH in someone with primary thyroid failure?

Answer 17

HIGH

Question 18

Describe the levels of thyroxine in someone with primary thyroid failure>

Answer 18

Low

Question 19

What is secondary hypothyroidism?

Answer 19

Problem with the pituitary

Question 20

What measurement is used to guide the dosage in secondary hypothyroidism?

Answer 20

as there is no TSH production, you guide dosage using free T4 levels and keep within reference range

Question 21

What is the clinical use of Liothyronine (t3)

Answer 21

Myxoedema coma

you give I.V. liothyronine as much faster than levothyroxine

Question 22

When might you give combined t3 and t4?

Answer 22

Some patients do not feel better with just t4, so give t3 as well as more potent

Question 23

What are some side effects of combined therapy of t3 and t4?

Answer 23

will suppress TSH completely, difficult to get right dosage

patients may complain about symptoms of thyrotoxicosis

Question 24

Describe some adverse side effects of thyroid hormone over replacement?

Answer 24

• increased bone turnover
• reduced BMD
• risk of osteoporosis
• increased energy expenditure
• weight loss
• tachy
• tremor
• nervousness

Question 25

What is the half life of t3?

Answer 25

2-5 days

Question 26

What is the half life of t4?

Answer 26

6 days

Question 27

What plasma protein is t3 and t4 bound to?

Answer 27

thyroxine binding globulin

Question 28

What can cause an increase in the production of plasma proteins?

Answer 28

pregnancy

prolonged treatment with oestrogen

Question 29

What can cause a decrease in the amounts of plasma proteins?

Answer 29

liver failure as most plasma proteins are made there

malnourishment