Presentation on theme: "Calcium / Vitamin D. Calcium metabolism Serum calcium drops.. PTH released.. In kidney, PTH turns vitamin D into its active form 1,25hydroxycholecalciferol."— Presentation transcript:
Calcium metabolism Serum calcium drops.. PTH released.. In kidney, PTH turns vitamin D into its active form 1,25hydroxycholecalciferol (calcitriol)... It also increases kidneys 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 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 10 2 There is no obvious cause. There is unexplained weight loss or anaemia or any other suggestion of coeliac disease or fat malabsorption.unexplained weight loss If medication (e.g. antiepileptic drugs, rifampicin) might be the cause.antiepileptic drugs 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).sarcoidosis tuberculosislymphomaprimary 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 e.g Adcal D3, Calceos – 10mcg / 400 units per tablet – Calcium and Ergocalciferol - vitamin D2 10mcg / 400 units per tablet Takes at least a year for bone to normalise. Higher doses may be needed. 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 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. Consider giving 800iu/d vitamin D to all >80 years. Groups that have been recommended to have combined calcium and vitamin D supplementation – 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 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 Oxford Handbook of General Practice 3 rd ed Patient.co.uk GP notebook BNF NHS choices