Calcium / Vitamin D
Calcium metabolism
• Serum calcium drops.. PTH released..
• In kidney, PTH turns vitamin D into its active
form 1,25hydroxycholecalciferol (calcitriol)... It
also increases kidney’s reabsorption of
calcium from urine
• Calcitriol acts to aid absorption of calcium
from small intestine
Calcium metabolism
• Dietary sources – Dairy (semi skimmed milk greater content than full
fat), sardines, bread, baked beans, cabbage
• PTH causes release of calcium from bone into
bloodstream.
• Absorption of calcium from blood into bone
matrix, stimulated by calcitriol
Vitamin D metabolism
• Vitamin D is produced by the skin in sunlight
(cholecalciferol - D3)
• Diet adequate in vitamin D is needed to maintain supplies
in Winter (D2 and D3)
• Dietary sources:
– Eggs, dairy products, oily fish, fortified cereals
• Skin and dietary sources of vitamin D are metabolised by
liver and then kidney, into active form
1,25hydroxycholecalciferol (calcitriol)
Vitamin D deficiency
• Inadequate mineralisation of bone matrix
• Leads to low calcium and phosphate, and secondary
hyperparathyroidism
• In children: Rickets
– Bone pain; skeletal deformity e.g bow legs, pigeon chest;
pathological #; poor growth; muscle weakness; dental
deformities
• In adults: Osteomalacia
– Bone pain – especially hip and low back pain; muscle
weakness; fatigue; pathological #; hypocalcaemia –
perioral and extremity numbness; hand/foot spasms;
arrhythmias
Risk factors
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Dark skin especially in Northern climes
Children and elderly
Pregnancy
Routine covering of face and body, e.g. wearing a veil.
An infant who has prolonged breast-feeding without
vitamin D supplementation, especially if the mother is
vitamin D-deficient – neonatal seizures
Housebound or institutionalised
Poverty.
Vegetarianism.
Alcoholism
Malabsorption, renal, liver and pancreatic disease.
Causes / treatment
• Dietary deficiency
• Age related – metabolism deteriorates with age
• Secondary osteomalacia - Malabsorption, renal, liver
and pancreatic disease
• Vitamin D dependent Rickets – rare genetic condition
affecting vit D metabolism
• Vitamin D resistant Rickets – genetic trait causing
reduced phosphate absorption from kidney
Investigations
• Children – paediatrics
• Renal and liver function (raised alk phos)
• Calcium, phosphate (may be low)
• Serum vitamin D and PTH – unless high risk and diagnosis clear
clinically
– Normal vitamin D level: above 50 nmol/L
– Vitamin D insufficient: 25-50 nmol/L
– Vitamin D deficient: below 25 nmol/L
• Consider radiology but may not be necessary if diagnosis clear
Referral
• All children with rickets should be referred to a paediatrician.10 It is
advisable to refer an adult with vitamin D deficiency to a relevant
specialist if:2
• There is no obvious cause.
• There is unexplained weight loss or anaemia or any other
suggestion of coeliac disease or fat malabsorption.
• If medication (e.g. antiepileptic drugs, rifampicin) might be the
cause.
• If the patient has hepatic or renal disease.
• If there is any illness associated with undue sensitivity to vitamin D
and so an increased risk of toxicity with treatment (e.g. sarcoidosis,
tuberculosis, lymphoma, primary hyperparathyroidism).
• Symptomatic patients who have taken supplements as directed for
about 2 months with no improvement clinically or in vitamin D
status.
Dietary deficiency Vitamin D treatment
• Advice about diet and sun exposure
• Prevention: 10mcg / 400 units per day (for those at high risk)
• Treatment: 20mcg / 800 units per day
• No plain vitamin D tablet available to treat simple dietary deficiency –
available either combined with calcium, or as combination vitamin tablets
– Calcium and Cholecalciferol – vitamin D3
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e.g Adcal D3, Calceos – 10mcg / 400 units per tablet
– Calcium and Ergocalciferol - vitamin D2
• 10mcg / 400 units per tablet
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Takes at least a year for bone to normalise. Higher doses may be needed.
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Lack of response – is there an underlying cause e.g malabsorption or renal failure?
Pregnancy / breast feeding / infants
• Vitamin D supplements recommended for all pregnant
and breast-feeding women and breast-fed babies:
– Pregnancy and breast-feeding: 10 micrograms (400 units)
of ergocalciferol daily (20 micrograms daily for those with
limited sun exposure and those whose diet is deficient in
vitamin D).
– Babies: all breast-fed babies should receive vitamin drops
(e.g Abidec). ?after 6 months only
– Infants who are breast-fed and children and adolescents
who consume less than 1 L of vitamin D-fortified milk per
day will likely need supplementation to reach 400 IU of
vitamin D per day.
Calcium and vitamin D in the elderly
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A review commentary stated that "..calcium plus vitamin D remains the
cornerstone of prevention of fractures in elderly people and patients with
osteoporosis".
– The doses of calcium and vitamin D were suggested as calcium >= 500mg per day and vitamin
D >= 800 IU per day.
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Consider giving 800iu/d vitamin D to all >80 years.
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Groups that have been recommended to have combined calcium and vitamin D
supplementation
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Over 70s in residential care
History of recurrent falls
History of a fragility fracture
Older patients with significant oral steroid use e.g. prednisolone 5mg or higher daily for three
months
– On bisphosphonates
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in the major trials where efficacy of bisphosphonates has been demonstrated also gave calcium, and
in all studies patients were vitamin D replete
Treatment of other causes
• Malabsorption or chronic liver disease
– Ergocalciferol - vitamin D2 - in pharmacological doses
• Ergocalciferol - Up to 1mg / 40 000 units per day
– Serum calcium levels being monitored to avoid
toxicity
– Alternatively treat with Calcitriol
• Alfacalcidol and Calcitriol.. For severe renal failure
(the other forms require hydroxylation by kidney)
Monitoring
• Serum calcium concentrations should be checked regularly for a few
weeks after starting treatment for vitamin D deficiency and then
vitamin D, parathyroid hormone (PTH) and calcium concentrations
should be checked after 3-4 months of treatment to assess efficacy
and adherence to therapy. Vitamin D and calcium concentrations
should be checked every 6-12 months
• Patients at risk of deficiency e.g elderly on long term prevention, up
to 20mcg / 800 units per day – no monitoring needed.
• But consider checking calcium prior to treatment, and check
calcium if nausea and vomiting
• Care with co-prescribing thiazide diuretic – increased calcium.
References
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Oxford Handbook of General Practice 3rd ed
Patient.co.uk
GP notebook
BNF
NHS choices