Parathyroids Flashcards
Normal Ca levels?
8.5 - 10.5 g/dl
What is active calcium?
unbound Ca (about 45%)
Most protein bound Ca associates with what protein?
albumin
What happens when someone is hypo-calcemic in terms of symptoms?
perioral paresthesia
tingling in fingers and toes
muscle carmps
seizures
Levels of Ca are modulated thru interplay between what other molecules and organ systems?
PTH
Vit D
calcitonin
and bone/kidney/GI
What cells in parathyroid gland make PTH?
chief cells
Chief cells of parathyroid glands make what hormone?
PTH
What effect does PTH have on serum Ca?
INCREASES Ca
When serum calcium levels fall low, what does parathyroids do?
increase serum Ca
Chief cells of parathyroids release PTH, how does PTH increase serum Ca?
bone–> stimulates osteoclasts to increase bone resorption
kidney–> stimulates Ca resorption and stimulates production of 1-25 dihydroxyvitamin d
intestine–> stimulates absorption of Ca and phosphate from gut
What does calcitonin do?
opposes PTH
tones down Ca
inhibits bone resorption
Where is calcitonin made?
parafolicular cells of thyroid
Vit D is ingested or made in precursor form, and it undergoes 2 hydroxylations;
1st–>first hydoxylation occurs at C 25 in the liver
2nd–>2nd hydroxylations occurs at C1 in the kidney in response to PTH
What effect does Vit D have on Ca levels?
gut–> increase Ca and phosphate resorption
bone–>stimulates bone resorption
Where do we tend to find the superior parathyroid glands vs the inferior parathyroid glands:
superior parathyroids–> postero-medial aspect of thyroid near tracheo-esophageal groove
inferior parathyroids–> below area of inferior thyroid artery
Blood supply to parathyroids?
inferior thyroid artery–> from thyrocervical trunk–>subclavians
Common sites for ectopic parathyroid glands are?
thyrothymic ligament
superior thyroid poles
tracheoesophageal groove
retroesophageal space
carotid sheath
Inferior parathyroids originate from what branchial pouch?
3rd branchial pouch
Superior parathyroids originate from what branchial pouch?
4th branchial pouch
Relationship of inferior parathyroids as they originate from the branchial pouches;
inferior parathyroids–> 3rd branchial pouch
superior parathyroids–> 4th branchial pouch
What cells make up the parathyroid glands?
chief cells—> PTH
oxyphill cells
80-90% of primary hyperparathyroidism caused by what?
parathyroid adenoma (usually a single gland)
What are three causes of primary hyperparathyroidism?
parathyroid adenoma (80-90%)
hyperplasia of parathyroid glands (10-15%)
parathyroid carcinoma (1%)
Whats MEN 1?
primary hyperparathyroidism
pancreas lesions
pituitary lesions