Endocrine L5: Thyroid Hormones

Question 1

What are 4 determining factors for the speed of metabolism?

Answer 1

1. Males > female
2. Age
3. Fitness (fit > not fit)
4. Higher thyroid activity (hormone) = increase metabolism

Question 2

What does metabolism refer to?

Answer 2

To all the chemical reactions occurring in the body (specific processes eg. breakdown of glucose)

Question 3

What are 2 things that metabolism includes?

Answer 3

1. External work (energy used by skeletal muscles to move)
2. Internal work (energy used to sustain life)

Question 4

What is external work in metabolism?

Answer 4

energy used by skeletal muscles to move

Question 5

What is internal work in metabolism?

Answer 5

energy used to sustain life

Question 6

What is metabolic rate?

Answer 6

Rate of energy expenditure (calories/hr or kJ/hr)

Question 7

What are the 2 components of metabolic rate?

Answer 7

1. Energy used at rest- “basal metabolic rate”
2. Additional energy used for activities

Question 8

BMR determined primarily by ____ hormones.

Answer 8

thyroid

Question 9

What are 5 thyroid gland and hormone?

Answer 9

1. Thyroid gland lies over the trachea in the neck
2. Contains follicles, comprised of follicular cells and colloid, that produce the thyroid hormones T3 & T4 from tyrosine and iodine
3. TH are amines, lipophilic, are transported in plasma bound to carrier proteins, with a balance between bound and free hormone
4. Most TH secreted as T4 which is converted to T3 in tissues – T3 is four times more potent (T4 —> broken down –> T3 (activated)
5. Virtually every tissue in the body affected by TH

Question 10

Virtually every tissue in the body affected by _____.

Answer 10

TH

Question 11

Where are the thyroid glands?

Answer 11

Question 12

Thyroid gland lies over the _____ in the neck

Answer 12

trachea

Question 13

The thyroid hormones contains ‘_____’, with follicular cells and colloid, produces the thyroid hormones ____ and ____ from tyrosine and iodine

Answer 13

follicles; T3; T4

Question 14

TH are _____, ______ transported in plasma bound to carrier proteins, with a balance between bound and free hormone

Answer 14

amines; lipophilic

Question 15

Most TH secreted as ____which is converted to ____ in tissues – ____ is four times more potent

Answer 15

T4 ; T3; T3

Question 16

What does TH synthesis and release look like?

Answer 16

Question 17

How do you make thyroid hormone?

Answer 17

• Combine iodine and tyroside
• Add a back bone (thyroglobulin) –> to store

Question 18

When do you need thyroid hormones?

Answer 18

• Instead of making it –> endocytose the backbone –> break of T3, T4
• Others are re-cycled

Question 19

What are 4 thyroid functions?

Answer 19

1. TH increases basal metabolic rate and increases heat production
2. Increases metabolism by influencing fuel metabolism (synthesis & breakdown of protein, fat and carbohydrates)
3. ‘Sympathomimetic’ effect – increases target cell responsiveness to catecholamines (This effects cardiac output by increasing HR and contractility) Increase in sympathetic NS by increase responsiveness of catecholamines
4. TH is permissive for growth and development (esp. CNS) – promotes effects of GH and somatomedins Wont work without –> permissiveness

Question 20

TH increases ______ rate and increases _____ production

Answer 20

basal metabolic; heat

Question 21

TH nncreases metabolism by influencing _____ metabolism (synthesis and breakdown of protein, fat and carbohydrates)

Answer 21

fuel

Question 22

What is the Sympathomimetic’ effect from TH?

Answer 22

increases target cell responsiveness to catecholamines (This effects cardiac output by increasing HR and contractility)

Question 23

TH is ______ for growth and development (esp. CNS) – promotes effects of GH and somatomedins

Answer 23

permissive

Question 24

What is the control of synthesis and release of TH?

Answer 24

Question 25

What are the 2 abnormalities of thyroid function?

Answer 25

Question 26

What are the 2 types of hypothyroidism?

Answer 26

1. Primary * Thyroid gland failure 2. Secondary * Deficiency of TRH or TSH * Inadequate supply of iodine

Question 27

What are the symptoms of hypothyroidism?

Answer 27

decreased metabolism, poor cold tolerance, excessive weight gain, fatigue, bradycardia, weak pulse, slow reflexes and mental function (Slow or slurred speech)

Question 28

What happens to hypothyroidism in adults?

Answer 28

myxodema (‘puffy’ esp. face) * Fluid in these areas

Question 29

What happens to hypothyroidism in neonates?

Answer 29

* cretinism & dwarfism irreversible unless treated from birth * Severe deficiency of growth and metabolism * Brain and immune system

Question 30

Why is it important to check thyroid function before getting pregnant?

Answer 30

Even a minor deficiency can have a massive impact on baby (esp. mental development --\> can drop the IQ by 15 points )

Question 31

What is the most common cause of hyperthyroidism?

Answer 31

Graves’ Disease – Autoimmune production of thyroid-stimulating immunoglobulin (TSI) which activates TSH-R inducing TH release

Question 32

What is Grave's Disease?

Answer 32

Autoimmune production of thyroid-stimulating immunoglobulin (TSI) which activates TSH-R inducing TH release (most common cause)

Question 33

What can hyperthyroidism be caused by?

Answer 33

by excess TRH, TSH or TH production (usually from tumour)

Question 34

What are symptoms of hyperthyroidism?

Answer 34

increased metabolism, excessive sweating, increased appetite but weight loss, muscle weakness, anxiety, palpitations, goitre

Question 35

Graves’ disease may also result in \_\_\_\_\_\_- (bulging eyes)

Answer 35

exophthalmos

Question 36

Why do thyroid supplements..etc not work?

Answer 36

Question 37

As TH decreases with _____ and low TH is more common for ____ (men/women), people start taking TH supplementary.

Answer 37

age; women