Endocrinology (Thyroid Gland) Flashcards
Where is the thyroid gland found
-lower neck below the thyroid cartilage
What is the structure of the thyroid follicle
-made of follicular cells that surround the colloid
What do follicular cells secrete?
-thyroid hormone
What is the colloid made of?
-glycoprotein
How many thyroid hormones do we have? What are they called?
-2: T3, T4 (thyroxine)
What structures are part of thyroid synthesis?
- follicular cells
- colloid
What is needed to make thyroid hormone?
- iodine; obtained through food (salt)
- absorbed through digestive system > blood stream
Thyroid synthesis process
1) Na+- symporter brings I- into the cell. The pending transporter moves I- into the colloid
2) Follicular cell synthesizes enzymes and thyroglobulin for colloid
3) Thyroid peroxidase adds iodine to tyrosine to make T3 and T4
4) Thyroglobulin is taken back into the cell in vesicles
5) Intracellular enzymes separate T3 and T4 from the protein
6) Free T3 and T4 enter the circulation
How are the thyroid hormones classified?
- amino acid derived
- tyrosine
What is the function on thyroglobulin?
-allow tyrosine, iodine to grab on
What is TRH?
- thyroid releasing hormone
- produced in the hypothalamus
- stimulates anterior pituitary gland
The TRH stimulates the anterior pituitary to produce what?
- TSH (thyroid stimulating hormone)
- stimulates the thyroid gland
What does the thyroid gland produce?
- T4: travels to target > cell takes it in > removes Iodine to make T3
- T3(active form),
When do we see negative feedback in a loop?
-when the last hormone level is too high
What is hyperthyroidism?
-overproduction of thyroid hormone
What causes hyperthyroidism?
-thyroid cancer
- Graves’ disease (autoimmune disease)
- stimulates thyroid gland
What are the effects of Graves’ disease?
-immune system is producing ‘thyroid stimulating immunoglobulin’ (TSI)
What is the other term for immunoglobulin?
-antibody
What are the symptoms of hyperthyroidism?
- increase in O2 consumption
- increase in metabolic heat production/ heat intolerant
- Increase in protein catabolism/ weight loss
- irritable/ insomnia
- tachycardia (increase in heart rate)
- goiter (enlargement of the thyroid gland)
- exophthalmus (bulging of the eye)
What is the cause of hypothyroidism?
-lack of iodine in diet
What are the symptoms of hypothyroidism?
- decrease in O2 comsumption
- decrease in metabolic heat production/colt intolerant
- decrease in protein synthesis= dry/thin skin, brittle nails, thinning hair ( decrease in protein keratin)
- slow speech/thought process
- fatigue
- bradycardia (slow heart rate)
- goiter (enlargement of thyroid gland)
- myxedema (fluid accumulation under the eye)
- cretinism (hypothyroidism during infancy)
