thyroid Flashcards
what is the body’s largest wholly endocrine gland?
thyroid gland
what is the most important function of the thyroid gland?
basal metabolism regulation
is the thyroid gland normally palpable?
no!
what is the term for palpable enlargement of the thyroid?
goiter
what cells contain iodide?
follicular cells of the thyroid
what cells secrete calcitonin?
parafollicular cells
what cells synthesize and secrete thyroglobulin?
follicular cells
what cells secrete T3 and T4?
follicular cells
what is the role of calcitonin?
ca++ and phosphorus metabolism
- decrease blood [ca++]
- increase urinary loss of ca++
what is the thyroid’s blood supply like?
it has the greatest blood flow per gram of tissue in the body
regulation of the thyroid gland is _____ dependent.
pituitary dependent
hormone regulation for the thyroid:
TRH (hypothalamus) -> TSH (pituitary) -> T3,T4 (thyroid)
what do vacuoles in the colloid indicate>
that the follicle is active
what is needed for the synthesis of thyroid hormone?
iodine
what are the 3 steps to liberation of T3 + T4??
- endocytosis by thyroid epithelial cells (colloid contains thyroglobulin)
- lysosomes fuse with endocytotic vesicles (lytic enzymes free thyroid hormones)
- free thyroid hormones diffuse from lysosomes, out of cell and into blood
how to thyroid hormones travel through the blood to target cells?
carrier proteins
which thyroid hormone is a prohormone?
T4 ->T3
is there more T3 or T4 in the blood?
there is 20X more T4 than T3 in the blood
T3/T4 breadown are de-iodinated and decarboxylated to become what?
thyronine
what is the parafollicular hormone?
calcitonin
what type of hormone is calcitonin?
poly-peptide hormone
what are the actions of calcitonin on osteoclasts and the kidneys?
- osteoclasts: blocks osteoclasts action (inhibits bone resorption)
- kidneys: blocks renal reabsorption of calcium and phosphorus
what is calcitonin’s action on PTH?
antagonistic
what causes goiter 90% of the time?
iodine deficiency
goiter is a sign of?
hyperthyroidism
what are other signs of hyperthyroidism?
- goiter
- heat insensitivity
- unkempt coat
- eye sign
- tachycardia
- weight loss
how can you test borderline hyperthyroid cases?
- differentiated by TSH stimulation test
- tumors aren’t stimulated by TSH
- thyroid scan
treatment for hyperthyroidism
- antithyroid drug
- radioactive idodine
- surgery
what disease is a deficiency of thyroid follicular hormones?
hypothyroidism
clinical signs for hypothyroidism
- elevated canine thyroglobulin auto-antibodies (detects autoimmune disease)
- alopecia on tail
- lethargy
- cold intolerance
- weight gain
- hyperpigmentation of skin
what is the treatment for hypothyroidism?
synthetic T4
