L3: The Thyroid Gland Flashcards
What is the largest endocrine gland?
Thyroid gland
Thyroid isthmus
Connects the right and left lobe of the thyroid gland
Thyroid follicles are functional units that release __
T3 and T4
Parafollicular cells (C cells) secrete
calcitonin
The thyroid gland is highly ______ with very ____ blood flow
highly, high
Follicular cells trap ____ and secrete it with ____ into lumen
iodine, thyroglobulin (TGB)
What is the active form of the hormone that the thyroid gland secretes?
T3
Draw the hypothalamic - pituitary - thyroid axis (HPT axis)
Steps of the TRH and TSH loop (5)
- Low blood levels of T3 and T4 OR low metabolic rate stimulates the release of
- TRH, carried by portal veins to anterior pituitary, stimulates release of TSH by thyrotrophs
How do T3 and T4 circulate?
They circulate bound to proteins. Free T3 is biologically active
What is the primary impact of thyroid hormones?
Basal metabolic rate and thermoregulation
What are other physiological effects of thyroid hormones?
Growth
CNS development
Cardiovascular
Metabolism
Where are T3 and T4 produced?
Follicular cells
What are the majority of steps in the HPT regulated by?
TSH
What 4 things fo thyroid hormones need?
iodide, tyrosine, thyroglobulin, thyroglobulin, thyroid peroxidase (TPO)
T3/T4 secreted into ___ and bound to ____
RBCs, bind to carrier proteins
What are disorders of the thyroid gland?
Hypothyroidism - congenital, endemic, goiter/iodine deficiency, myxedema
Hyperthyroidism
Congenital hypothyroidism
Lack of thyroid hormone production during fetal life, infancy, and childhood.
-Lack of functioning thyroid gland
Endemic hypothyroidism. Cause and symptoms
Lack of thyroid hormone or lack of iodine
Stunted growth, a slow fusion of bones, intellectual disability
What is the treatment for congenital/endemic hypothyroidism?
Iodine therapy and/or thyroxine if early enough before significant growth impairment
Endemic goiter
Enlarged thyroid gland from iodine deficiency
Idiopathic goiter
Deficiency in
iodine trapping
peroxidase coupling
deiodinases
Treatment for goiter
Iodine replacement therapy
Combination therapies target idiopathic goiter
Prenatal vitamins contain iodine
Myxedema (untreated hypothyroidism)
Swelling of face and neck interstitial fluid
Can lead to coma and death
It is the lack of thyroid function
What is the most common endocrine disorder?
Hypothyroidism (myxedema (untreated hypothyroidsim))
How do you treat hypothyroidism?
replace thyroxine
Hyperthyroidism
Common: increased thyroid function and suppressed feedback on TSH
Uncommon: localized adenoma (tumour)
Treatment of hyperthyroidism
Reduce TH production (thionamides)
Surgical removal of thyroid gland
