Path - calcium Flashcards by Thivyaa Gangatharan

Where does PTH obtain calcium from when there’s hypocalciemia?

Bone
Renal reabsorption via the activation of 1 alpha hydroxylase

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What does 1 alpha hydroxylase do?

Activate vitamin D -> this also increases gut calcium absorption

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PTH is a protein or steroid? What does it do?

84 amino acid protein
stimulates 1 alpha hydroxylase
stimulates phosphate excretion in order to maintain calcium phosph balance and stop crystals from increasing in blood (vit D causes phosphate and calcium retention via gut).

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What happens to 7 dehydrocholestrol when in the sun?

It makes cholecalciferol

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What happens to cholecalciferol and where? What is another name for this?

VIt D3 - First pass metabolism - 100 percent hydroxylated to 25 hydroxycholecalciferol

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What is the plant vitamin vitamin D?

Vit D2 - ergocalciferol

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1 alpha hydroxylase can also be expressed where else in which condition?

Ectopically expressed in the lungs - can cause hypercalcemia in sarcoidosis

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What is the product of 1 alpha hydroxylation of 25 cholecalciferol?

CALCTRIOL also called 1 25 cholecalciferol

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Who do you prescribe calcitriol to?

ONLY to renal patients who can’t 1 alpha 25 hydroxylase

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What does calcitriol do?

Increases calcium and phosphate absorption from gut

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Where is alk phosph released?

Liver and bones

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When is alk phosph released from bones?

When there is bone formation

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Define osteomalacia

Defective bone mineralisation

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Clinical features of osteomalaica/rickets on xrays

Looser’s zone fractures

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Biochemical features of osteomalacia

Low calc
Low phosph
Raised ALP as the bone is trying to heal

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Signs of rickets

Bowed legs
Costrochondral swelling
widened epiphyses at the wrists
Myopathy

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What else can cause rickets?

Anticonvulsants

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Risk factors for osteomalacia

Phytic acid chelates vit D
Renal failure
Lack of sunlight

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Define osteoporosis

Slow loss of bone mass, causing bone mineral density

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Biochemical features of osteoporosis

Normal calcium
Normal phosph
Normal alk phosph

What is the first feature of osteoporosis?

Neck of femur fracture, colles, vertebral fracture

Where do you do a DEXA scan?

Hip
Spine
Wrist

What are the scores for DEXA and what do they mean?

Compare with someone who is young - T score

Z score - SD from mean of aged-matched control

What do you call it when your bone isn’t as strong as it should be for your age?

Failure to attain peak bone mass

Causes of osteoporosis

Early menopause

LIfestyle causes of osteoporosis

sedentary EtOH smoking Low BMI/poor diet

Endo causes of osteoporosis

Hyperprolactinomia Thyrotoxicosis CUshings

LIfestyle interventions for osteoporosis

Weight bearing exercise Stop smoking Reduce eTOH

Give an example of

Alendronate - has nitrogen and phosphate, and nitrogen isn't biodegradable so osteoclasts have a hard time breaking it down, so it's really strong It needs to be taken by itself because it will become inactivated if taken with calcium, e.g. milk Therefore needs to be taken once a week with a glass of water Also, it irritates their stomach so

ALternative

IV Xolandronate - once every year

Give an example of a PTH derivative used for osteoporosis

Teriparatide

Strontium

Calcium

Give example of oestrogen targeting drugs for osteoporosis

Selective estrogen receptor modulator - raloxifene or tamoxifen (antagonistic oestrogen in breast, agonist in bone, has opposite effects - increases bone density and prevents breast cancer)

SE of osteoporosis

Worsen the symptoms of menopause

NORMAL calcium levels

2.2 to 2.6 millimoles per litre (mmol/L)

How much of bone is calcified?

two thirds of bone is calcified

Hypercalcemia symptoms

Polyuria/polydipsia Constipation

If calcium is high and PTH is normal, what's the diagnosis?

Parathyroid problem - PTH should be undetectable if calcium is high

If there's hypercalcemia, what do you have to check?

PTH - is it suppressed?

Causes of primary hyperparathyroidism

Parathyroid adenoma Hyperplasia or carcinoma MEN 1 syndrome

3 ways in which hypercalcemia is created by malignancy

PTHrp - kidney, breast cancer Bone mets osetolysis Haematological malignancies - Cytokines

TREATMENT for acute hypercalcemia

Normal saline 4 L of normal saline daily, until the calcium lowers

If the patient has hypercalcemia of malignancy, what do you give?

BISPHOSPHONATES always avoid bisphosphonates unless you know for sure they have cancer, as otherwise it will drop the calcium levels when you have parathyroid surgery

Signs of hypocalcemia

Chvostek's sign Trousseau's sign Hyperreflexia Seizure - at this point we've missed the boat :( Laryngeal spasm - can cause death

Explain Trousseu's sign

Take BP - bp cuff causes Albumin rises binds to free calcium therefore muscles become active and patients get carpal spasm

Define Paget's

Focal disorder of bone remodelling

Signs of paget's

Focal pain Warmth Deformity Fracture SC compression Malignancy Cardiac failure as more blood is going through that bone

Biochemical results for paget's

Elevated alk phosph, everything else is normal

Rank higherst to lowest calcium

Breast cancer - highest Primary hyperparathyroidism Osteoporosis/pagets - normal calcium Osteomalacia/secondary hypoerparathyroidism