Endocrinology Flashcards
what is the active form of the thyroid hormone?
T3
what is the symporter that brings Iodine into the follicle cells?
NIS - sodium iodine symporter
what is the enzyme that adds iodine to tyrosine?
thyroid peroxidase
once t3 and t4 are made, how are they transported into blood circulation once it is done being made?
they are hydrophobic, so they are transported into circulation by thyroxine-binding globulin and albumin (made in liver)
when one iodine is added to the tyrosine-thyroglobulin structure, what is it called? when two are added?
one iodine = MIT
two iodine = DIT
what does MIT and DIT stand for?
Monoiodotyrosine and diiodotyrosine
how are t3 and t4 formed?
t3 = mit + dit
t4 = dit + dit
what is the release pathway for thyroid gland?
hypothalamus - TRH
anterior pituitary - TSH
thyroid gland - T3 and T4
what is hyperthyroidism, and two causes of it?
too much production of t3 and t4; cause 1: thyroid cancer (tumor growth in thyroid gland) and cause 2: grave’s disease (autoimmune disease, stimulates thyroid gland)
what are the symptoms of hyperthyroidism?
- higher 02 consumption
- high metabolic heat production = heat intolerant
- protein catabolism = weight loss
- irritable/insomnia
- tachycardia (high hr)
- goiter
- exopthalamus (swelling behind eyeballs)
what is a cause of hypothyroidism?
not enough t3 and t4, caused by lack of iodine in diet
what are the symptoms of hypothyroidism?
- lower 02 consumption
- lower metabolic rate = cold intolerant
- protein synthesis = dry/think skin, brittle nails, thin hair
- slow speech/thought process
- fatigue
- bradycardia (low hr)
- goiter
- myxedema (eye bags)
- cretinism (slow development mentally during infancy)
is hypothyroidism treatable?
yes, just add iodine to diet
does hyperthyroidism initiate negative feedback? how about hypothyroidism?
hyperthyroidism does, hypothyroidism doesn’t
what is the growth hormone release?
hypothalamus - GHRH
anterior pituitary - GH
liver and other tissues - insulin-like growth factors
what is the inhibitory hormone in growth hormone release?
somatostatin; released from the hypothalamus
what do the IGF’s affect in the growth hormone release?
cartilage, bone, and tissue growth, higher blood glucose
what is pituitary drawfism?
when you don’t have enough GH from the anterior pituitary. it causes stunt in bone growth and this happens in childhood
what is giantism?
when there is a GH oversecretion in childhood; tumor growth in the pituitary gland
what is acromegaly?
it is GH oversecretion in adulthood
what is the parathyroid hormone?
its a gland behind the thyroid gland releasing this hormone.
what triggers the release of parathyroid hormone?
low blood concentration of calcium Ca2+ levels
when the parathyroid hormone is released into the bloodstream, what is the main goal?
to raise blood plasma Ca2+ levels
when the parathyroid hormone is released into the bloodstream, what series of events are triggered? (aka where do we get the Ca2+ ions from?)
- increase in osteoclast activity (breaking down bone to receive Ca2+ ions)
- this results in bone resorption, which is breaking down the bone - increase in renal Ca2+ reabsorption (takes Ca2+ out of urine before it is excreted)
- increase in intestinal Ca2+ absorption (taking Ca2+ out of the diet through vitamin D3)
what is calcitrol, and where is it located?
it is vitamin D3 and located from exposure to sunlight, and also the diet.
do we convert cholesterol into vitamin d3?
yes
what are the steps that calcitrol increases blood ca2+ levels?
- increase osteoclast activity
- increase renal resorption
- increase intestinal Ca2+ absorption with PTH
what is calcitonin and where is it located?
it is triggered by too much blood ca2+, so it lowers blood ca2+ levels. it is located and synthesized in the thyroid gland (in the cell outside of the follicle)
what are the steps that calcitonin trigger?
- inhibits osteoclast activity
- increase renal ca2+ secretion
what is osteoporosis?
bone loss; stimulates osteoblasts
