Thyroid/GI Flashcards
What are the hormone steps to get to thyroid hormone secretion?
- Hypothalamus secretes TRH
- TRH stimulates AP to secrete TSH
- TSH stimulates Thyroid to secrete hormones
What feedback takes place in the HPT axis?
- TSH inhibits Hypothalamus TRH secretion
- Thyroid hormones inhibit both TRH (hypothalamus) and TSH (AP) secretion
What are the two primary functions of the thyroid?
- Follicular cells producing Thyroxine (T4) and Triiodothyronine (T3)
- Parafollicular cells producing calcitonin
Increased basal metabolic rates and heat production (calorigenic effects) are caused by what?
Thyroid hormones
______ is produced exclusively by the thyroid gland whereas _______ is primarily produced extrathyroidally
T4, T3
*T3 is 4x more potent than T4
What converts T4 to T3?
Deiodinase enzymes
*Can be converted to Reverse T3 which is inactive
When the body is stressed/fasting what changes in regards to Thyroid hormone?
- Converts less T4 to T3
- Converts more T4 to rT3 (to conserve energy)
How does the thyroid store T3 and T4?
as thyroglobulin in follicles
Outer ring deiodination results in?
T3 (active)
Inner ring deiodination results in?
rT3 (inactive)
At what time in life do women need more iodine than men?
Pregnancy and breast feeding
What two things typically cause Goiter?
- Too much TSH
- Too much hCG
Extreme Iodine deficiency in mothers diet during pregnancy can result in congenital hypothyroidism known as?
Cretinism
*Dwarfism, Reduced BMR, Delayed puberty, infertility
Hashimoto’s is an autoimmune disease resulting in?
Hypothyroidism
Graves disease is an example of?
Hyperthyroidism
