CALCIUM-REGULATING HORMONES

Question 1

What is the concentration of calcium in the blood of mammals ?

Answer 1

-10 mg/dL

Question 2

Calcium in plasma or serum exists in three forms/fractions. What are these ?

Answer 2

• Protein bound calcium
• Ionized or free calcium
• Complexed or chelated calcium

Question 3

This form of calcium accounts for approx. 1/3 of the total serum calcium concentration; cannot diffuse through membranes and thus is not usable by tissue

Answer 3

Protein-bound calcium

Question 4

Form of calcium that is physiologically active that accounts for 50% - 60% of total Ca concentration

Answer 4

Ionized or free calcium

Question 5

Form of calcium bound to phosphate, bicarbonate, sulfate, citrate, and lactate and accounts for 10% of the total Ca concentration

Answer 5

Complexed/chelated calcium

Question 6

What are the 3 major hormones that interact to maintain a constant concentration of calcium ?

Answer 6

• PTH
• Vitamin D
• Calcitonin

Question 7

What are the hormones that contribute to the maintenance of calcium homeostasis ?

Answer 7

• Adrenal corticosteroids
• Estrogens
• Thyroxine
• Somatotropin
• Glucagoon

Question 8

This hormone mobilizes calcium from bone and increase urinary phosphate excretion.

Answer 8

PTH

Question 9

This hormone increases calcium absorption from the intestine .

Answer 9

1,25 - Dihydroxycholecalciferol

Question 10

This hormone inhibits bone resorption.

Answer 10

Calcitonin

Question 11

Where is PTH synthesized ?

Answer 11

Chief cells of PTH gland

Question 12

What are the compounds that can influence PTH secretion ?

Answer 12

• Biological amines
• Peptides
• Steroids
• Drugs

Question 13

This hormone controls calcium concentration in the ECF.

Answer 13

PTH

Question 14

The effect of PTH is mediated indirectly by regulation of synthesis of the active metabolite of ?

Answer 14

Vitamin D

Question 15

Each parathyroid gland is about the size of ?

Answer 15

Grain of rice

Question 16

PTH raises the blood calcium level by ?

Answer 16

• Breaking down the bone causing calcium release
• Increasing the body’s ability to absorb calcium from food
• Increasing the kidney’s ability to hold on to calcium that would otherwise be lost in the urine

Question 17

Calcitonin is ___-amino acid polypeptide hormone.

Answer 17

32

Question 18

Calcitonin is secreted by ?

Answer 18

Parafollicular cells (C cells) of the thyroid gland

Question 19

What is the principal stimulus for the release of calcitonin ?

Answer 19

Concentration of calcium ion in ECF

Question 20

Calcitonin exerts it effects by interacting with target cells, primarily in ?

Answer 20

bone & kidney

Question 21

PTH & Calcitonin is antagonistic on ? but synergistic on ?

Answer 21

bone resorption; decreasing the renal tubular reabsorption of phosphorus

Question 22

Vitamin D3 (Cholecalciferol) came from what origin ?

Answer 22

Animal

Question 23

Vitamin D2 (Ergocalciferol) came from what origin ?

Answer 23

Plant

Question 24

This hormone is involved in the regulation of calcium metabolism and skeletal remodeling .

Answer 24

Vitamin D

Question 25

Vitamin D will be hydroxylized in the liver and kidneys forming ?

Answer 25

active 1,25 - dihydroxyvitamin D (calcitriol)

Question 26

Identify the metabolic diseases associated with calcium-regulating hormones with the given data: * A metabolic state characterized by an excessive, but not autonomous, rate of PTH secretion * Encountered frequently in dogs Occurs occasionally in cats * The secretion of hormone by the hyperplastic parathyroid glands usually remains responsive to fluctuations in blood calcium levels * Longstanding, progressive renal disease resulting in severely impaired function * Chronic renal insufficiency in older dogs results from interstitial nephritis, glomerulonephritis, nephrosclerosis, or amyloidosis

Answer 26

Secondary hyperparathyroidism (renal hyperparathyroidism)

Question 27

Identify the metabolic diseases associated with calcium-regulating hormones with the given data: * Is produced in excess of normal by a functional lesion in the parathyroid gland * Encountered infrequently in older dogs * Does not appear to be a sequela of long-standing secondary hyperparathyroidism in animals * The normal control of PTH secretion by the concentration of blood calcium is lost in primary hyperparathyroidism * Hormone secretion is autonomous

Answer 27

Primary hyperparathyroidism

Question 28

Prolonged increased secretion of PTH can lead to ?

Answer 28

Accelerated osteocytic and osteoclastic bone resorption

Question 29

Identify the metabolic diseases associated with calcium-regulating hormones with the given data: * A metabolic disorder in which PTH-like polypeptides or other bone-resorbing substances are secreted in excessive amounts by malignant tumors of nonparathyroid origin

Answer 29

Hypercalcemia of Malignancy (Pseudohyperparathyroidism)

Question 30

Identify the metabolic diseases associated with calcium-regulating hormones with the given data: * Metabolic disorder in which either subnormal amounts of PTH are secreted by pathologic parathyroid glands or the hormone secreted is unable to interact normally with target cells * Recognized in dogs, particularly smaller breeds such as schnauzers and terriers * Variety of pathogenic mechanisms can result in an inadequate secretion of PTH * Parathyroid glands may be damaged or inadvertently removed during the course of thyroid surgery * When damaged, regeneration of adequate functional parenchyma and subsequent disappearance of clinical signs occurs

Answer 30

Hypoparathyroidism

Question 31

Identify the metabolic diseases associated with calcium-regulating hormones with the given data: * Less known about its pathogenesis in dogs and cats than in cow * Puerperal tetany is encountered most frequently small, hyperexcitable breeds of dogs and occasionally in the cat * Clinical course → rapid, the bitch may proceed from premonitory signs of: ---Restlessness ---Panting ---Nervousness to ataxia ---Trembling ---Muscular tetany ---Convulsive seizures in 8 to 12 hours * Hyperthermia frequently is associated with the increased muscular activity, and elevations of body temperature to 107iF are not uncommon * Eclampsia → puerperal tetany * Eclampsia in heavily lactating bitches is the result of an interference in PTH secretion * 1-3 weeks postpartum → may develop hypocalcemia and often hypophosphatemia

Answer 31

Hypocalcemic Syndromes Associated with Parturition

Question 32

Identify the metabolic diseases associated with calcium-regulating hormones with the given data: * Abnormalities in the secretion of CT are recognized much less frequently than disorders of PTH in both animals and humans * A hypersecretion of CT has been reported in: --- Humans --- Bulls --- Laboratory rats

Answer 32

Hypercalcitonism

Question 33

Identify the metabolic diseases associated with calcium-regulating hormones with the given data: * Lack of CT secretion (have not been recognized either humans or animals) * Thyroidectomized animals are less able than normal animals to handle a high calcium meal and may develop postprandial hypercalcemia

Answer 33

Hypocalcitonism