Healthy bones and metabolism Flashcards by Hager Meghrawi

How much calcium does the body contain?

~ 1kg (25mol)

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What is the percentage of calcuim in our body that is in our bones?

99%

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How much calcium travels in the body and from and to where?

approximately 500mmo1/240 moves between bone and ECF

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What forms are calcium in the body

Diffusible (ion complexed to lots of proteins, slows it and able to diffuse as it is bigger)- which can be spilt into
‘Free’ calcium- physiologically active(ionised calcium)
Complexed to proteins
Protein bound

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Which form of calcium is homeostatically managed?

‘Free’ calcium

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How is calcium used around the body? Describe calcium cycle in body

From bone to ECF- Bone resorption and exchange
From ECF to bone- 
Bone formation and exchange
Formation and resorption in balance
Kidney to ECF - Reabsorption
Plasma to kidney-
Glomellular filtration
Gut to Plasma- Absorption
Plasma to Gut - 
Secretion
Food to gut
gut to faeces
Plasma to skin thorugh sweating

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What is bone resorption?

Bone broken down and calcium and phosphate taken back into ECF
Otherwise known as reuptake

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What is reabsorption?

Not breaking down anything but taking up ions

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What regulates calcium ? 3

Parathyroid hormone
Vitamin D
Calcitonin

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Where is Parathyroid hormone secreted from? Where is that?

Parathyroid glands which sit on four corners of the thyroid gland on the neck

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The process of secreting Parathyroid hormone-Size of each form

First- Pre pro PTH- 115 amino acids

> Pro PTH- 90 amino acids
> Mature PTH- 84 amino acids

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What does PTH do and where?

In Kidney:
Increases calcium resorption/ reuptake in distal tubules
Increases phosphate excretion
Increases formation of active vitamin D

In Bone:
Stimulates bone resorption

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How does PTH regulate calcium when it is at a low level?

Hypocalcemia- stimulus detected
Trigger Calcium Sensing Receptor in Parathyroid gland (CaSR)
Increases PTH

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What is hypocalcemia

Low calcium

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What does increasing bone resorption do?

Increases calcium and phosphate

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What does Increasing calcium resorption

Increasing formation of active vitamin D do?

Decreases phosphate resorption

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How would you describe results of measurements that are abnormal? why?

NOT abnormal
SAY Appropiate
Because if someone has a low level of calcuim, it would be expected to see high levels of PTH therefore better to say appropiate than high or low

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What are the common forms of Vitamin D?

Most common are Vitamin D2 and Vitamin D3

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What is Vitamin D derived from? How can you tell from the structures?

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Cholesterol

Steroid backbone

Where is most Vitamin D derived from?

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UV light on skin

What is Vitamin D2 used as?

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Food additive

What food source contains Vitamin D?

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Oily fish

How is vitamin D overally sythesised

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dehydrocholesterol in skin turned into Vitamin D3 Cholecalciferol by UV light

Is Vitamin D3 (cholecalciferol) biologically active?

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Activation of Vitamin D? Where?

In liver Vitamin D3 (Cholecalciferol) undergoes hydroxylation so becomes Calcidol/ 25(OH)D / 25-hydroxycholecalciferol Reaction is dependent upon availability of substrate (Vitamin D) In kidney 25(OH)D undergoes enzymatic reaction Enzyme- 1α hydroxylase Which changes 25(OH)D into 1,25-dihydroxycholecaIciferol

Is Calcidol/ 25(OH)D / 25-hyclroxycholecalciferol biologically active?

How is the activation of Vitamin D in kidney regulated?

decreased phosphate decreased 1,25-OHD increased PTH

Is 1,25(OH)D biologically active?

yes

What does activated Vitamin D do?

In bone- Stimulates bone resorption In Intestine- Stimulates calcium absorption Stimulates phosphate absorption

When do we look at abonormal Vitamin D Levels and PTH levels?

Calcium and ohosphate levels If in same direction- Vitamin D If in different directions- PTH

What is Vitamin Deficiency called in adults

Osteomalacia

What is Vitamin Deficiency called in chilldren

Rickets

What is calcitonin?

32 amino acids protein

What secretes calcitonin and from where?

parafollicular cells of the parathyroid gland

What does calcitonin do?

Opposes the effect of PTH

What happens if there are high levels of calcium

Thyroid gland releases calcitonin -> | Inhibit osteoclast activity and Calcium reabsorption on the kidney decreased-> calcium levels dropped

What is bone density?

A measure of the amount of mineral present in the bone

Why is bone density measured

Used to diagnose osteoporosis

What is it a factor for?

A contributing factor to the fracture risk

What is a DEXA scan?

Scans for bone density

What can affect bone density- 8

Calcium intake Calcium absorption — Vitamin D (sun exposure and dietary factors) Functionality of PTH — Magnesium deficiency Weight bearing exercise Smoking — affects bone turnover BMI Healthy diet — oily fish, whole grains, cut down on fat and sugar Hormones Steroid hormones, oestrogen, thyroid hormones

What is osteopaenia?

Lower bone density

What do vegans eat to supplement calcium

need leafy green vegetables, almonds, sesame seeds.Pulses, tofu

What do people with lactose intolerance eat to supplement calcium

- pilchards, curly kale, watercress, sesame seeds

Factors that contributes to fracture risk? 6

``` Age Previous fracture Alcohol intake Smoking status Medication (steroids) Bone density ```

What happens to bone density in women over time? Why?

Bone density in women decreases after the menopause | decreasing oestrogen levels

Healthy bones and metabolism Flashcards

(46 cards)