Lecture 4 Flashcards
(32 cards)
What is the functional unit of thyroid gland?
Follicle
What protein is the colloid of the thyroid follicle filled with?
Thyroglobulin
Name the a.a. + Iodine according to number of iodine molecules
One = monoiodotyrosine (MIT)
Two = di-iodotyrosine (DIT)
Three = tri-iodotyrosine (T3)
Four = Thyroxine (T4)
What form is 90% of TH released as?
T4
Compare T3 and T4
T3 is 4X more physiologically active than T4
T3 has a shorter half life in plasma than T4
1-2 vs 2-6 days
How is TH transported?
>99% is bound to plasma proteins such as thyroxine-binding globulin, albumin and other proteins
T4 is converted to more active T3 in some peripheral tissues (kidney and liver)
Where are TH receptors found>
Intracellulary - nuclear
Two general metabolic effects of TH
Controls basal (resting) metabolic rate and oxygen consumption
Calorigenic (produces heat, burns energy)
How does TH control basal (resting) activity?
Regulates activity of Na/KATPase pumps (more energy required if more active)
Effect of TH on cellular oxygen consumption?
Increase TH will increase cellular oxygen consumption
Why would animals decrease TH release during hibernation?
Dont want to keep burning up their energy storage
WHat are the nutrient metabolism effects of TH?
- Low [TH] = anabolic effects,
- glucose —> glycogen
- protein synthesis - High [TH] = catabolic effects
- Glycogen —> glucose
- Protein break down
Cardiovascular effects of TH?
Increase heart rate
Increase force of contraction
3 ways TH can increase cardiac output?
- Increase beta-adrenergic receptor number
- Increase myosin in cardiac muscles
- Increase activity of Na and Ca pumps
What are the effects of TH on CNS?
TH is essential for normal neural function
Effect of TH on growth>
TH required for GH secretion from pituitary
- Increase TH doesn not result in excess growth, h/e low TH can result in stunted growth
Effects of TH on hair
Low TH leads to dry coat, excess shedding and alopeica
Effect of TH on skin?
Low TH can lead to puffy skin
What stimulates the release of TH?
TSH from anterior pituitary
What inhibits release of TSH?
TH - primary negative feedback inhibition
Why is TRH release stimulated in cold environments?
TRH stimulates TSH which stimulates TH release, this increase heat production. Especially important in young animals
4 Types of hypothyroidism
Iodine deficiency
Primary Hypothyroidism
Secondary/Tertiary Hypothyroidism
Cretinism/ Secondary Dwarfism
Reason for hypothyroidism
Iodine Deficiency
TH cannot be produced without iodine
Reason for hypothyroidism
Primary Hypothyroidism
Thyroid Gland not working properly
