P1 Spring Organs 2011-03-31 (Parathyroid, Calcium, And Phosphorus)

Front 1

Where is vitamin D3 made?

Back 1

Precursor comes from skin, then liver and kidneys hydroxylate it.

Front 2

Where does parathyroid hormone (PTH) come from?

Back 2

Parathyroid gland

Front 3

Where does calcitonin come from?

Back 3

The parafollicular cells (C cells) of the thyroid gland.

Front 4

List what 1,25-dyhydroxycholecalciferol does?

Back 4

↑Ca+ resorption from bone (bone → plasma)
↑Ca+ reabsorption in kidneys
↑Ca+ absorption in intestines
↑osteoblast and osteoclast activity
↑Phosphate absorption from intestines

Front 5

List all the names of vitamin D3.

Back 5

1,25-dyhydroxycholecalciferol
Vitamin D3
Calcitroil

Front 6

List what PTH does.

Back 6

↑Ca+ reabsorption from kidneys
↑Ca+ resorption from bones
↓Phosphate reabsorption by kidneys
↑Vitamin D3 (and therefore stimulates all of vitamin D3's effects)

Front 7

List what calcitonin does.

Back 7

↓Ca+ absorption from intestines
↓Ca+ reabsorption by kidneys
↓Ca+ resorption from bone
↓Phosphate reabsorption by kidneys
During prenancy ↑Vitamin D3 and ↓Ca+ resorption to shuttle Ca+ into bones, preventing bone loss

Front 8

Why would bone loss occur during pregnancy if not for ↑calcitonin?

Back 8

Ca+ from mom's bones is used to build/maintain babies skeleton, and to make milk.

Front 9

What do osteoclasts do?

Back 9

They remove bone tissue during bone resorption, which releases Ca+ into the blood.

Front 10

Purpose of calcitonin?

Back 10

Prevent hypercalcemia (normally)
↑Ca+ in bones (pregnancy)

Front 11

How is inorganic phosphate reabsorbed by the kidneys?

Back 11

There are NaPi (sodium phosphate) symporters in the proximal tubules.
Note that PTH inhibits these.

Front 12

How does vitamin D3 increase Ca+ absorption in intestines?

Back 12

Vitamin D3 increases expression of:
Calbindin-D (ca+ binding protein)
Ca+ ATPase
TRPV6 (Ca+ channel)

Front 13

Where are the parathyroid glands?

Back 13

There are 4 of them, two embedded within each thyroid gland, which are in the neck (next to the pharynx).

Front 14

What are the cells of the parathyroid gland, and their purpose?

Back 14

Chief cells: secrete PTH
Oxyphil cells: uncertain function, but dont secrete PTH

Front 15

Describe the pathway(s) that are activated when PTH attaches to a receptor on a bone cell.

Back 15

AC → cAMP
PLC converts PIP2 to IP3 and DAG
IP3 releases Ca+ from bone cell (as part of bone resorption)
DAG activates PKC

Front 16

What is PTHrP?
Where is is found?
Where is it produced?

Back 16

PTH related protein.
Found in smooth muscle, in tooth enamel, in keratinocytes in the skin.
Produced by different tissues in the body (not like PTH which is just produced by parathyroid)

Front 17

What are the effects of PTHrP?

Back 17

Growth of cartilage in the uterus.
Protects neurons against excitotoxic damage
Involved in Ca+ transport in the placenta

Front 18

What does absence of PTHrP cause in babies?

Back 18

Teeth cannot erupt to the surface.

Front 19

What is a C cell?

Back 19

A "clear cell" (a parafollicular cell of the thryroid gland)

Front 20

List everything that stimulates calcitonin secretion.

Back 20

When plasma Ca+ level exceeds 9.5 mg/dL
Gastrin (most potent stimulator)
B-adrenergic agonists
Dopamine
Estrogens
CCK (cholecystokinin)
Glucagon
Secretin

Front 21

What effect do glucocorticoids have on Ca+ levels?

Back 21

Lowers plasma Ca+ level by inhibiting osteoclast formation and activity

Front 22

Causes of osteoporosis?

Back 22

Inhibiting osteoclast formation or activity.
High Ca+ levels.
Osteoclast stimulation by cytokines (osteoclast stim in general?)
(me) too little or too much osteoclast activity, need balance of osteoblast and osteoclast activity.

Front 23

What effect does GH have on Ca+ levels?

Back 23

↓Ca+ reabsorption by kidneys
↑Ca+ absorption by intestines
Overall though you get and increase in Ca+

Front 24

What effect does IGF-1 have on Ca+ levels?

Back 24

Stimulates protein synthesis in bone.
Note IGF-1 is produced when GH levels increase

Front 25

What effect do thyroid hormones have on Ca+ levels?

Back 25

Hypercalcemia
Hypercalciuria
Possible osteoporosis

Front 26

What effect does insulin have on Ca+ levels?

Back 26

Increases bone formation
This is why IDDM can cause bone loss, and perhaps later stage of NIDDM (when little insulin is produced)

Front 27

What hormone can prevent osteoporosis?

Back 27

Estrogens

Front 28

List treatments for hypercalcemia.

Back 28

Saline rehydration (to ↑blood volume)
Loop diuretic (↑urine production)
Calcitonin
Glucocorticoids
IV Bisphosphonate
Mithramycin
Gallium nitrate
The idea of many of these is to excrete the excess Ca+ in the urine.

Front 29

What is the common cause of hypercalcemia?

Back 29

Hyperparathyroidism

Front 30

List common symptoms of hypercalcemia.

Back 30

Brain: lethargy, confusion
Muscles: weakness
GI: loss of appetite, N/V (nausea/vomiting)
Renal: Polyuria, thirst (polydipsia)
Heart: ↑contractility
Eye: irritation, calcification
Bones: pain, fracture

Front 31

List causes of hypocalcemia.

Back 31

↓albumin (transport protein?)
↓Mg+ (?)
hypoparathyroidism
Drugs/concurrent meds
Vit D deficiency/malabsorption
Liver disease (cant make vit D)
Kidney disease (cant make vit D)

Front 32

Treatment for more severe hypocalcemia?

Back 32

Oral or IV soluble calcium salts, eg Calcium chloride