HORMONES THAT REGULATES CALCIUM HOMEOSTASIS Flashcards
Daily net changes in calcium are as follows:
- About ___mg of Ca 2+ is ingested per day.
- Only ___ of this is absorbed from the intestine (___mg) and enters ECF.
- Part of Ca 2+ in ECF is lost through ___ secretion (___mg) back into the gut.
- ____% of calcium is in skeleton
1000
1/3
360
enteric; 190
99
FORMS OF CALCIUM IN THE BLOOD
-The total Ca 2 ± concentration in blood is normally __ mg/ dL
- Of the total Ca 2 ± , __% is bound to plasma proteins, mainly _____.
- The ultrafilterable component includes a (small or large?) portion that is complexed to _____ (e.g., phosphate, sulfate, and citrate) and free, ionized Ca Ca 2 ± 2 ± .
10
40
albumin
small
anions
The Free, ionized Calcium amounts to ___% of the total (i.e., __ mg/ dL), and it is the only form of Ca2+ that is biologically ____
50
5
active.
Forms of calcium in blood
____% bound to protein
____% ultrafiltratable(___-to anions; ____-free)
40
60
10
50
Hypocalcemia
Symptoms are:
- (hyporeflexia or hyperreflexia?)
- spontaneous ____
- muscle _____
- _____ and ____
hyperreflexia
twitching
cramps
tingling and numbness
Chvostek sign: ____ of the ____ muscles elicited by tapping on the ____ nerve
Seen in Hyp__calcemia
twitching
facial
facial
O
Trousseau sign: which is _____ upon inflation of a ______
Xterics of hyp__calcemia
carpopedal spasm
blood pressure cuff
O
Hypercalcemia
-Manifestations of hypercalcemia include
____
poly___
poly____
neurologic signs of ___reflexia
constipation
uria
Dipsia
hypo
lethargy and coma
Hypercalcemia or hypocalcemia
Hypercalcemia
PARATHYROID HORMONE
-The ____ cells of the parathyroid glands synthesize and secrete PTH, a single chain polypeptide with ___ amino acids.
chief
84
PARATHYROID HORMONE
The molecule’s biologic activity resides entirely in the _ terminal __ amino acids.
N; 34
When the plasma Ca 2+ concentration ___eases, PTH is secreted by the parathyroid glands.
Decr
Mechanism of parathyroid hormone Action
- PTH binds on receptor on the renal ____ at the _____ membrane
- The receptor is coupled, via a _____ A
proximal tubule
basolateral
adenylyl cyclase
Inhibition of Na +– phosphate phosphate cotransport results in ___eased phosphate reabsorption and ____
Decr
phosphaturia
REGULATION OF PTH
Action on bone
- PTH has several actions on bone, some direct and some indirect.
- In bone, receptors are located on osteo___ but not on osteo____
Blasts
Clasts
REGULATION OF PTH
Action on bone
-after binding to the receptors on osteo___
Initially and briefly, PTH causes an ___ease in bone formation by a direct action on ___. (This brief action is the basis for the usefulness of ____ PTH administration in the treatment of ____
Blasts
Incr
osteoblasts
intermittent
osteoporosis
REGULATION OF PTH
Action on bone
In a second, ___ lasting action on osteoclasts, PTH causes an increase in resorption. This second action on osteoclasts is (direct or indirect?) and mediated by _____ released from osteoblasts.
long
indirect
cytokines
osteoblasts, are required for the boneresorbing action of PTH on osteoclasts
T/F
T
Parathyroid hormone
Action on Kidney
(A)PTH ____ phosphate reabsorption by inhibiting ______ cotransport in the ____
inhibits
Na + phosphate
PCT
Parathyroid hormone
Action on kidney
PTH ____ Ca 2+ reabsorption.
This second renal action of PTH is on the ___ and complements the increase in plasma Ca 2+ concentration that resulted from the combination of bone resorption and phosphaturia
stimulates
DCT
Parathyroid hormone
Action on INTESTINE
PTH (directly or indirectly?) act by stimulating renal _____, the enzyme that converts 25hydroxycholecalciferol to the active form of vitamin D 1 , 25 hydroxy chole calciferol
indirectly
l α hydroxylase
Pathophysiology
(A)Primary hyperparathyroidism
- commonly caused by _____ (tumors) which secrete excessive amounts of PTH.
- Persons with primary hyperparathyroidism are said to have “stones’ “bones,” and “groans”
- stones from _____
- bones from ____ased bone resorption
- groans from _____.
- treatment is by _____ of the parathyroid glands.
parathyroid adenomas
hypercalciuria
incr
constipation
surgical removal
Secondary hyperparathyroidism
-the parathyroid glands are ____ but are stimulated to secrete _____ PTH secondary to hypocalcemia, which can be caused by ____ deficiency or ____ failure.
In this, PTH levels are (elevated or depressed?) but blood levels of Ca are __ or _____ but never ____.
normal
excessive
vitamin D
chronic renal
elevated
low; normal; high
Hypoparathyroidism.
- Commonly occurs because of ____ or ______ , while ______ and ____ hypoparathyroidism are less common.
- Characterized by low circulating levels of PTH, hypocalcemia, and hyperphosphatemia.
- Treatment: combination of an _____ supplement and the _____ of _____
thyroid surgery or parathyroid surgery
autoimmune and congenital
oral Ca 2+
active form of vitamin D.
Pseudohypoparathyroidism
- First described by ____ in ____.
- Patients present ___calcemia, ___phosphatemia, and a characteristic phenotype consisting of (short or tall?) stature, (short or tall?) neck, obesity, subcutaneous ______, and (shortened or lengthened?) ___ metatarsals and metacarpals and thus called _______
Fuller Albright
1940
Hypo; hyper
short; short
calcification
Shortened
fourth
Albright’s hereditary osteodystrophy.
Humoral hypercalcemia of malignancy.
- Some malignant tumors (e.g., lung, breast) secrete ______ rp ), with similar structure and functions that PTH possesses
- similar Outcome that is seen in _____
- However, in humoral hypercalcemia of malignancy, circulating levels of PTH are ___ because PTH secretion by the parathyroid glands, which are normal, is suppressed by the hypercalcemia.
-Treatment:_____ which inhibits renal Ca 2+ reabsorption , and increases Ca 2+ excretion, and inhibitors of bone resorption such as ______.
PTH related peptide
primary hyperparathyroidism.
Low
Furosemide
etidronate
Calcitonin
- Calcitonin is a straight chain peptide with ____ amino acids.
- the major stimulus for calcitonin secretion is ____ased plasma Ca 2+ concentration .
- The major action of calcitonin is to ____ osteoclastic bone resorption, which decreases the plasma Ca 2+ concentration.
32
incre
inhibit; decreases
calcitonin participates in the minute to minute regulation of the plasma Ca 2+ concentration in humans.
T/F
F
Vitamin D
-Comes from 2 main sources: Diet (vitamin D_ or ___calciferol) Skin(vitamin D_ or ____calciferol)
2; ergo
3; chole
Vitamins D2 and D3
Identical in structure
Have identical functions
T/F
F
T
(Passive or Active?) transport of Ca 2+ from the intestine is increased by a metabolite of vitamin D
T/F
Active
T
While PTH role is to maintain the plasma Ca 2+ concentration and increase the ionized Ca 2+ concentration toward normal.
-The role of vitamin D is to promote _____ of ____ , and its actions are coordinated to increase both concentrations in plasma___ and ____ so that these elements can be deposited in new bone mineral.
mineralization of new bone
Ca 2+ and phosphate
Synthesis of Vitamin D
- There are two sources of cholecalciferol in the body:
- From ingested diet or synthesized in the skin from _____ in the presence of ____
7dehydrocholesterol
ultraviolet light.
Cholecalciferol is physiologically (active or inactive?)
It is ____ in the ____ to form _____ that is (active or inactive?) .
inactive
hydroxylated
Liver
25hydroxycholecalciferol
Inactive
In the ___, 25hydroxycholecalciferol, is further ___ to produce _____, which is the physiologically (active or inactive ?) form.
-this process is catalyzed by the enzyme _____, which is regulated by several factors, including the plasma Ca concentration and ___.
kidney
hydroxylated
1,25 dihydroxycholecalciferol
Active
1a hydroxylase
PTH
Actions of Vitamin D
- In the Intestine: Ca 2+ 1,25dihydroxycholecalciferol ____
- On the Kidney. The actions of 1,25dihydroxycholecalciferol on the kidney are parallel to its actions on the intestine . it stimulates ______.
- On the Bone. It acts _____ with ____ to stimulate osteo_____ activity and bone ____.
increases calcium and phosphate absorption
both Ca 2+ and phosphate reabsorption
synergistically with PTH
clast
resorption
Initial action of active vitamin D3 on bones may seem paradoxical, since the overall action of 1,25dihydroxycholecalciferol is to promote bone mineralization.
However, mineralized “__” bone is ____ to provide more Ca 2+ and phosphate to ___ so that “__” bone can be mineralized (bone ______ ).
old; resorbed
ECF
new
remodeling
DEFICIENCY of vitamin D
(1) Rickets: a condition in _____ in which ____ amounts of calcium and phosphate are available to mineralize the growing bones. Rickets is characterized by ___ failure and _____ deformities.
This condition is rare in areas of the world where ____ is supplemented and when there is adequate exposure to ____
children
insufficient
growth; skeletal
vitamin D
sunlight
DEFICIENCY of vitamin D
Osteomalacia : vitamin D deficiency in ____
It’s a condition in which new bone fails to ___, resulting in ____ and ____ of the _____ bones.
Adults
mineralize
bending and softening
weight bearing
DEFICIENCY of vitamin D
Vitamin D resistance: occurs when the ____ is unable to _______ .
Vitamin D resistance can be caused by the _____ of _____ or, more commonly, by _______ failure.
kidney
produce the active metabolite, 1,25 dihydroxycholecalciferol
congenital absence; l αhydroxylase
chronic renal
Effects of other hormones on calcium homeostasis
Estrogens
- prevents _____ by a (direct or indirect?) effect on osteoblasts. through _____ of stimulatory effect of certain ____
osteoporosis
direct
Inhibition
cytokines
Effects of other hormones on calcium homeostasis
Insulin
-____eases the action of bone formation
Incr
there is little bone loss in untreated Diabetes MELLITUS
T/F
F
It’s significant
Effects of other hormones on calcium homeostasis
Insulin- like growth factor (IGF1)
- stimulates protein ____ in bone
synthesis
Effects of other hormones on calcium homeostasis
Growth hormone
- ___eases Ca 2+ excretion in urine
- ___eases intestinal absorption
-Effect of GH results in a ____ Ca 2+ balance
Incre
Incr
+ ve
Effects of other hormones on calcium homeostasis
Glucocorticoids
- Over long periods it cause _____ by ___eased bone formation and __eased bone reasorption.
- ____ease bone formation by ____ protein synthesis in osteoblasts
- ___eases the Absorption of Ca by an anti2+ & PO 4 from intestine Vit D action and ___ renal excretion of these ions.
osteoporosis; decr; incr
Decreases
inhibiting
Decreases
increase
