Lecture 32 Flashcards
What are two similarities between T3 and T4?
- they both haver an obligatory requirement for iodine
- the basic function of the thyroid hormones is to increase the basal metabolic rate
What is a differences between T3 and T4?
T3 has three iodine molecules, whereas T4 only has a total of four by contrast
What is the main thyroid hormone that is circulating in the blood?
T4
What is the most active form of the thyroid hormone?
T3
What state is most of the circulating hormones in the blood in?
Most of the hormones circulating in the blood will be bound to plasma proteins
Which hormone has the most potent feedback mechanisms and how does it act to inhibit release?
T4- has a negative feedback TSH from the anterior pituitary and also the hypothalamus
Briefly describe the process of thyroid hormone synthesis:
- Iodine is actively transported into the cell via a sodium symporter
- Iodine is attached to tyrosine inside the cell forming DIT and MIT
- These are then linked together to form the hormones, two DIT makes a T4, MIT and DIT make
What are the general effects of thyroid hormone?
Increases the basal metabolic rate of all tissues
How is the synthesis of thyroid hormones regulated?
- TRH (thyrotropin-releasing-hormones) is released from the hypothalamus
- TSH (thyroid stimulating hormone) is then released from the anterior pituitary
- Thyroid hormone synthesis at thyroid gland
What is hyperthyroidism and what are the general clinical signs that are associated with it?
- abnormally high levels of T3 and T4
- Metabolic effects: weight loss despite an increased appetite
- Cardiovascular effects: tachycardia and cardiac murmur
What is hypothyroidism and what are some of the clinical symptoms observed in hypothyroidism?
- decrease in production of T3/T4 occurs
- can be primary or secondary
- most of the clinical signs are associated with a decrease in the basal metabolic rate
- metabolic features include a lethargy and weight gain
