Calcitonin and PTH

Name FIVE of the major functions of Calcium.

Bone and teeth formation

Neuronal activity

Muscle activity

Cell division/growth

Blood coagulation

Excitability of nerves/muscles

Integrity of cell membrane

Hormone secretion

Hormone signaling mediator

Why did Erwin Neher and Bert Sakmann win a 1991 Nobel Prize?

Function of single ion channels in cells

Who studied how signals are transmitted from one nerve to another in the brain and the role of calcium by identifying molecular machinery triggering Ca2+ and vesicle fusion, thereby explaining how temporal precision is achieved and how signaling substance can be released from vesicles on command?

GOOD GOD I DONT CARE

Thomas C. Sudhof

True or False: Phosphate is a key element in all known life forms.

True!

Name FOUR major roles of phosphate.

Biological molecules (RNA/DNA/phospholipids/nucleotides)

Structural component of cell membranes

pH regulation

Cellular energy transport via ATP (glycolysis/energy metabolism)

Indicate which is higher, calcium or phosphate, in the following parameters:

ECF

Cell

Bone (apatite crystals)

ECF: phosphate

Cells: phosphate

Bone: calcium

In the blood, 50% of calcium is ————, 40% is bound to ———, and 10% is bound to ———-.

Free/ionic

Proteins

Citrate/phosphate

What is the normal range of calcium and phosphorus in the blood?

Calcium: 8.5-11 mg/dl

Phosphorus: 2.5-5 mg/dl

What are the four gland located normally on posterior surface of upper and lower poles of the thyroid?

Parathyroid glands

Name the TWO cell types of the parathyroid gland. Give a function if one is known.

Chief cells- secrete PTH (synthesized as preprohormone)

Oxyphil cells- unknown function

PTH (increases/decreases) blood calcium levels.

This (increases/decreases) calcium release from bone and (increases/decreases) renal excretion of calcium.

Increases

Increases

Decreases

PTH (increases/decreases) blood phosphate levels.

This (increases/decreases) phosphate release from bone and (increases/decreases) phosphate excretion from the kidneys.

Decreases

Increases

Increases

What TWO major things does PTH do to bone?

Increase osteocyte lysis

Increase osteoclast (reabsorption)

What THREE things does PTH do to the kidneys?

Increase calcium reabsorption

Decrease phosphate reabsorption

Decrease sodium reabsorption (weak effect)

What TWO things does PTH do in the intestines?

Increase calcium absorption

Increase phosphate absorption

What bone cell secretes collagen and ground substance to form osteoid?

Osteoblasts

How do osteoblasts become osteocytes?

Trapped in osteoid

What bone cell is a monocyte derivative and dissolves bone? It is active almost all of the time.

Osteoclasts

In general, what happens during the rapid and slow phases of PTH in terms of bone?

Rapid: osteolysis (calcium removal)

Slow: osteoclast activation (resorb bone)

What are the TWO major renal effects of PTH?

Decrease phosphate reabsorption

Increase calcium reabsorption

What is the MAJOR gastrointestinal effect of PTH?

Enhance calcium and phosphate absorption in intestinal mucosa

As an indirect effect of the GI impacts of PTH, what metabolite is formed in the kidney?

1,25-dihydroxycholcaliferol (vitamin D)

PTH protects calcium levels by immediately responding to an (increase/decrease) of Ca2+ in the blood. It acts quickly on — and —- to restore calcium to normal.

What happens if PTH is chronically elevated?

Decrease

Bone

Kidney

Bone loss

Name TWO things aside from low ECF Ca2+ that can stimulate PTH release.

What inhibits its secretion and gene expression?

Low Mg

High PO4

Active vitamin D

True or False: Vitamin D is limited when exposed to light and has little biologic activity.

True!

Which mf won a Nobel Prize in 1928 for his vitamin D research?

Adolf Windaus

PTH, calcium, phosphate, and vitamin D increase 1-alpha enzyme activity in times of (deficiency/excess) and increase the 24-hydroxylase enzyme activity in times of (deficiency/excess).

Deficiency

Excess

Name ONE action of vitamin D in the following locations:

GI tract

Kidney

Bone

GI Tract: increase calcium and phosphate absorption

Kidney: increase calcium and phosphate reabsorption (weak)

Bone: osteoblast/osteocyte pump

What can occur in orderly mineralization with active vitamin D in bone? What about in excess?

Rickets

Bone mineral dissolves (usually caused by rodenticides)

What cell secrete calcitonin and where?

Parafollicular cells

Thyroid follicles

What are the TWO major bone effects of calcitonin?

Decrease osteoclast absorption

Decrease osteoclast formation

Calcitonin is of particular importance in what stages of life? (2)

Young

Pregnant

Does thyroid removal impact calcium balance in adults in calcium and vitamin D are normal in the diet?

Nah

When is calcitonin secreted?

blood calcium levels are high

Calcitonin from what animal can be used to treat some bone diseases and reduce high blood levels of calcium?

Salmon

What happens in hypocalcemia? (2)

INCREASED neuron excitability (Na channels)

Tremors/tetany/seizures

What happens in hypercalcemia? (3)

DECREASED neuron excitability

Lethargy

Weakness

What happens in the absence of PTH?

Death rapidly occurs from asphyxiation caused by pronounced spasms of respiratory muscles

Carpopedal tetany is related to what condition?

Primary hypoparathyroidism

The following symptoms are characteristic of what condition?

Low PTH in presence of hypocalcemia

Decreased myocardial contractility

CNS changes

Impaired Ca2+ absorption in gut

Primary hypoparathyroidism

What kind of cats are likely to develop primary hypoparathyroidism?

Cats who undergo thyroidectomy for hyperthyroidism as a complication

The following symptoms are characteristic of what condition?

Oversecretion of PTH in presence of hypercalcemia

Normal/low phosphate

Primary hyperparathyroidism

What enzyme rises in primary hyperparathyroidism and serves as an important diagnostic indicator?

Alkaline phosphatase

What condition is a cystic bone disease that results from excess bone resorption, which can be caused by primary hyperparathyroidism?

Osteitis fibrosa cystica

What condition is characterized by normal parathyroid glands but a failure to respond to PTH with increased phosphate levels and low calcium levels? How do you treat it?

Some clinical signs include short stature, round face, short and thick neck, obesity, and metacarpal shortening.

Pseudohypoparathyroidism

Vitamin D and Calcium

What mutations can leave to hypocalcemia and hypercalciuria genetically?

CASR

What condition is characterized by vitamin D deficiency, GI disorders, chronic renal failure, and phosphate depletion?

Rickets (osteomalacia)

Do men or women get osteomalacia?

Women

What condition is associated with chronic renal failure, leading to failure to excrete phosphate -> binding to the free calcium -> increase PTH -> impaired vitamin D formation?

Renal secondary hyperparathyroidism

What condition deals with a dietary imbalance of phosphorus and calcium where high phosphorus lowers ionized calcium which in turn increases PTH, causing severe skeletal disturbance?

Nutritional secondary hyperparathryoidism

What is the most ratio of phosphorus and calcium in the diet?

1:1

What is the most common nutritional bone disease in dogs?

Nutritional secondary hyperparathyroidism

What condition can be caused by ingestion of rodenticides containing vitamin D or antipsoriatic ointments containing vitamin D analogues, treatment of hypoparathyroidism, or excessive dietary supplementation of vitamin D?

Hypervitaminosis D