Endocrine L5: Thyroid Hormones Flashcards
What are 4 determining factors for the speed of metabolism?
- Males > female
- Age
- Fitness (fit > not fit)
- Higher thyroid activity (hormone) = increase metabolism
What does metabolism refer to?
To all the chemical reactions occurring in the body (specific processes eg. breakdown of glucose)
What are 2 things that metabolism includes?
- External work (energy used by skeletal muscles to move)
- Internal work (energy used to sustain life)
What is external work in metabolism?
energy used by skeletal muscles to move
What is internal work in metabolism?
energy used to sustain life
What is metabolic rate?
Rate of energy expenditure (calories/hr or kJ/hr)
What are the 2 components of metabolic rate?
- Energy used at rest- “basal metabolic rate”
- Additional energy used for activities
BMR determined primarily by ____ hormones.
thyroid
What are 5 thyroid gland and hormone?
- Thyroid gland lies over the trachea in the neck
- Contains follicles, comprised of follicular cells and colloid, that produce the thyroid hormones T3 & T4 from tyrosine and iodine
- TH are amines, lipophilic, are transported in plasma bound to carrier proteins, with a balance between bound and free hormone
- Most TH secreted as T4 which is converted to T3 in tissues – T3 is four times more potent (T4 —> broken down –> T3 (activated)
- Virtually every tissue in the body affected by TH
Virtually every tissue in the body affected by _____.
TH
Where are the thyroid glands?
Thyroid gland lies over the _____ in the neck
trachea
The thyroid hormones contains ‘_____’, with follicular cells and colloid, produces the thyroid hormones ____ and ____ from tyrosine and iodine
follicles; T3; T4
TH are _____, ______ transported in plasma bound to carrier proteins, with a balance between bound and free hormone
amines; lipophilic
Most TH secreted as ____which is converted to ____ in tissues – ____ is four times more potent
T4 ; T3; T3
What does TH synthesis and release look like?
How do you make thyroid hormone?
- Combine iodine and tyroside
- Add a back bone (thyroglobulin) –> to store
When do you need thyroid hormones?
- Instead of making it –> endocytose the backbone –> break of T3, T4
- Others are re-cycled
What are 4 thyroid functions?
- TH increases basal metabolic rate and increases heat production
- Increases metabolism by influencing fuel metabolism (synthesis & breakdown of protein, fat and carbohydrates)
- ‘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
- TH is permissive for growth and development (esp. CNS) – promotes effects of GH and somatomedins Wont work without –> permissiveness
TH increases ______ rate and increases _____ production
basal metabolic; heat
TH nncreases metabolism by influencing _____ metabolism (synthesis and breakdown of protein, fat and carbohydrates)
fuel
What is the Sympathomimetic’ effect from TH?
increases target cell responsiveness to catecholamines (This effects cardiac output by increasing HR and contractility)
TH is ______ for growth and development (esp. CNS) – promotes effects of GH and somatomedins
permissive
What is the control of synthesis and release of TH?
What are the 2 abnormalities of thyroid function?
What are the 2 types of hypothyroidism?
- Primary
- Thyroid gland failure
- Secondary
- Deficiency of TRH or TSH
- Inadequate supply of iodine
What are the symptoms of hypothyroidism?
decreased metabolism, poor cold tolerance, excessive weight gain, fatigue, bradycardia, weak pulse, slow reflexes and mental function (Slow or slurred speech)
What happens to hypothyroidism in adults?
myxodema (‘puffy’ esp. face)
- Fluid in these areas
What happens to hypothyroidism in neonates?
- cretinism & dwarfism irreversible unless treated from birth
- Severe deficiency of growth and metabolism
- Brain and immune system
Why is it important to check thyroid function before getting pregnant?
Even a minor deficiency can have a massive impact on baby (esp. mental development –> can drop the IQ by 15 points )
What is the most common cause of hyperthyroidism?
Graves’ Disease – Autoimmune production of thyroid-stimulating immunoglobulin (TSI) which activates TSH-R inducing TH release
What is Grave’s Disease?
Autoimmune production of thyroid-stimulating immunoglobulin (TSI) which activates TSH-R inducing TH release (most common cause)
What can hyperthyroidism be caused by?
by excess TRH, TSH or TH production (usually from tumour)
What are symptoms of hyperthyroidism?
increased metabolism, excessive sweating, increased appetite but weight loss, muscle weakness, anxiety, palpitations, goitre
Graves’ disease may also result in ______- (bulging eyes)
exophthalmos
Why do thyroid supplements..etc not work?
As TH decreases with _____ and low TH is more common for ____ (men/women), people start taking TH supplementary.
age; women
