HORMONES THAT REGULATES CALCIUM HOMEOSTASIS Flashcards by Iseoluwa Ojo

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

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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 ± .

albumin

small

anions

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The Free, ionized Calcium amounts to ___% of the total (i.e., __ mg/ dL), and it is the only form of Ca2+ that is biologically ____

active.

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Forms of calcium in blood
____% bound to protein
____% ultrafiltratable(___-to anions; ____-free)

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Hypocalcemia

Symptoms are:

(hyporeflexia or hyperreflexia?)
spontaneous ____
muscle _____
_____ and ____

hyperreflexia

twitching

cramps

tingling and numbness

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Chvostek sign: ____ of the ____ muscles elicited by tapping on the ____ nerve

Seen in Hyp__calcemia

twitching

facial

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Trousseau sign: which is _____ upon inflation of a ______

Xterics of hyp__calcemia

carpopedal spasm

blood pressure cuff

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Hypercalcemia

-Manifestations of hypercalcemia include

____
poly___

poly____

neurologic signs of ___reflexia

constipation

uria

Dipsia

hypo

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lethargy and coma

Hypercalcemia or hypocalcemia

Hypercalcemia

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PARATHYROID HORMONE

-The ____ cells of the parathyroid glands synthesize and secrete PTH, a single chain polypeptide with ___ amino acids.

chief

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PARATHYROID HORMONE

The molecule’s biologic activity resides entirely in the _ terminal __ amino acids.

N; 34

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When the plasma Ca 2+ concentration ___eases, PTH is secreted by the parathyroid glands.

Decr

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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

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Inhibition of Na +– phosphate phosphate cotransport results in ___eased phosphate reabsorption and ____

Decr

phosphaturia

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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

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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

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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

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osteoblasts, are required for the boneresorbing action of PTH on osteoclasts

T/F

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Parathyroid hormone
Action on Kidney
(A)PTH ____ phosphate reabsorption by inhibiting ______ cotransport in the ____

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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

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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

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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.

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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 ____.

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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 _____

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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

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

HORMONES THAT REGULATES CALCIUM HOMEOSTASIS Flashcards

(46 cards)