L6: The Parathyroid Gland Flashcards
Chief cells produce _
PTH
Oxyphil cells
Absent in infants and children
Appear at puberty
Role unknown
Where is calcitonin produced in thyroid glands
Parafollicular cells (C cells)
Low Ca stimulates ..
PTH
High Ca stimulates
calcitonin
What are the physiological effects of PTH?
Bone, Kidney -> intestine
We do not want Ca and ___ to be reabsorbed at the same time
PO4
What are the 3 effect of PTH?
Bone: bone reabsorption and Ca efflux
Kindey: Increase in 1,25 Dihydroxycholecalciferol, increase in Calcium and decrease in PO4 reabsoription
Intestine: Increased Ca and PO4 absrobed at the same time
How is PTH activated?
A decrease in calcium detected by the CaSR
What is the half life of PTH?
4mins (short)
PTH causes an increase in Ca reabsorption and PO4 _____
excretion
Activates calcitriol to increased Ca and PO4 absorption in the
GI
What are the target organs of PTH?
Bones and kidneys
PTH _____ Ca from bones
releases
Where is calcitonin released from?
Parafollicular cells (c cells) in thyroif
What works antagonitsically to PTH?
Calcitonin
Calcitonin _____ with an increase in Ca
increase
What is a stronger regulator of Ca? PTH or calcitonin
PTH
How does calcitonin protect against hypercalcemis
lowering serum Ca
What activates calcitriol?
PTH
THe active form, vitamin D3 requires
PTH
Composition of bone __% inorganic _% organic
65% inorganic - hydroxyapatite
35% organic - osteoid
Inorganic bone is for
compressional strength
organic bone is for
tensile strength
What are the 3 types of bone cells?
Osteoblasts (bone formation)
Osteoclasts (resorption)
Osteocytes (trapped osteoblasts mature bone cells)
2 types of bone tissue
cortical - 80% of bone mass (outside layer)
Trabecular - 20% (cont being replaced)
4 disorders associated with the parathyroid gland?
Rickets - osteomalacia
Osteoporosis
Hyperparathyroidism
Hypoparathyroidism
Rickets - osteomalacia
Calcium or phosphate deficiency
Normally related to a decrease in vitamin D
Mainly seen in children
If untreated, PTH secretion will increase bone osteoclast activity and lead to weak bones
Treatment for rickets
Vitamin D plus calcium and phospate replacement
Basis for vitamin D supplements in milk and bread (fortified)
Osteoporosis
Most common bone disease in adults
Decreased bone matrix due to decreased osteoblast activity
Malnutrition, post-menopausal changes in estrogen, reduced GH and lack of bone matrix, Cushing’s syndrome (too much cortisol decreases osteonblast activity)
Treatment for osteoporosis
Biphosphonates
Bind to bone surface and slow osteoclast resorption of bone
Allows osteoblasts to work more effectively
Hyperparathyroidism
Innapp secretion of PTH
Incease in bone resorbtion
Increase calcium/phosphate levels
Kidney stones
adenoma on parathyroid glands
Treatment for hyperparathyroidism
removal of adenoma
Hypoparathyroidism
Too little PTH
Hypocalcemia
Muscle twitches and spasms that can lead to tetany
Damage to parathyroid gland (thyroidsectomy, autoimmune)
Treatment for hypopara
Calcitriol and Ca supplements
