Lecture23: Thyroid Gland Flashcards
What 3 hormones does the Thyroid Gland secrete?
T4, T3, Calcitonin
What is the main form secreted by the Thyroid Gland?
T4
A large amount of T4 is converted to T3 in the peripheral tissues via enzyme…?
Deiodinase
Where does the conversion of T4 to T3 take place? 3 places
Gut, liver and kidneys
What are the TH effects on metabolic rate?
They increase the metabolic rate and thermogenesis
How does TH increase protein synthesis?
Via enhancing the actions of other hormones
The conversion of Glucose to glycogen requires how much TH?
Little
The breakdown of Glycogen into Glucose requires how much TH?
A lot
Does TH increase Fat metabolism?
Yes
Up to which point of fetal life does the fetus depend on the thyroxine passinf from the placenta?
11 weeks
During which trimester of pregnancy does the Fetal Thyroid become active?
Second Trimester
The THs are essential for the nervous system why?
Mylelination, growth of brain during first two years
The THs increase which very important receptors the heart?
The Beta-1 adrenergic receptors
How does TSH act to regulate the thyroid gland?
It increased cAMP in the thyroxine
TH has a direct negative feedback effect on which pituitary?
Anterior
What form of TH is responsible for most of the negative feed back?
T4
Dietary iodine, when decreased, how does it affect the thyroid function?
Decreases it
What is GOITER?
Thyroid enlargement when TSH increases
What is the Hyperthyroidism disease called?
Graves Disease
What is Hypothyroidism in adults called?
Myxedema
What is Hypothyroidism in children called?
Cretinism
What is Thyrotoxicosis?
An increase in the circulating thyroid hormones
An example of Primary Thyrotoxicosis?
Graves’ disease
What is Secondary Thyrotoxicosis?
Pituitary adenoma or pharma caused
Explain Graves’ disease?
Antibodies stimulate the TSH receptor, thus no negative feedback mechanism
Name manifestations of graves?
Huge gland and increased synthesis rate
What are cardiac symptoms of graves?
Tachycardia and a wide pulse pressure
Does graves manifest in huge bulging eyes?
Yes
What are causes of Cretinism?
No thyroid, or no synthesis of hormones
Signs of cretinism?
Short, dull and constipated
Manifestations of hypothyroidism?
Decreased BMR, no cold tolerance
