Dr Terence Ong is a Research Fellow at Nottingham University Hospitals NHS Trust.
Professor Opinder Sahota is Professor of Orthogeriatric Medicine and Consultant Physician at Nottingham University Hospitals NHS Trust
Vitamin D is not, in the truest sense, a vitamin because it is not exclusively obtained through diet alone. It is a secosteroid, mostly obtained intrinsically by the effect of ultraviolet radiation on previtamin D compounds and subsequent hydroxylation in the liver and kidneys.
Vitamin D plays an important role in calcium and phosphate homeostasis through its effect on gut and bone metabolism. Besides that, it also plays a key role in muscle function. In recent years, our understanding of vitamin D has expanded and we are starting to appreciate its much broader role in areas such as the immune system, cancer and cardiovascular disease.
Low levels of vitamin D are highly prevalent in the British population, especially in the elderly. The cause is multifactorial – a combination of reduced sunlight exposure due to reduced mobility, reduced dietary intake, malabsorption, low skin thickness reducing previtamin D synthesis and impaired hydroxylation in the liver and kidneys. Left untreated this leads to impaired bone metabolism, pain, muscle weakness and osteomalacia.
The National Osteoporosis Society (NOS) has recently published clinical guidance on the management of vitamin D and bone health on 23rd April 2013. Its guidance covers aspects of determination of vitamin D status, treatment of any deficiencies, monitoring and identification of vitamin D toxicity.
Key summaries from the guidance includes:
- Measurement of serum 25OHD is the best way of estimating vitamin D status
- Serum 25OHD measurement is recommended for:
- Patients with bone disease that may improve with vitamin D treatment
- Patients with bone disease where correcting vitamin D deficiency is appropriate prior to specific treatment
- Patients with musculoskeletal symptoms that could be attributed to vitamin D deficiency
- Vitamin D thresholds adopted
- Serum 25OHD <30nmol/L – deficient
- Serum 25OHD of 30-50nmol/L – may be inadequate in some people
- Serum 25OHD >50nmol/L is sufficient for almost the whole population
- Oral vitamin D3 is the treatment of choice in vitamin D deficiency
- Where rapid correction of vitamin D deficiency is required, the recommended treatment regimen is based on fixed loading doses followed by regular maintenance therapy:
- A loading regimen to provide a total of approximately 300,000 IU vitamin D, given either as separate weekly or daily doses over 6 to 10 weeks
- Maintenance therapy in doses equivalent to 800 – 2000 IU daily
- Adjusted serum calcium should be checked 1 month after completing the loading regimen or after starting vitamin D supplementation in case primary hyperparathyroidism has been unmasked
- Routine monitoring of serum 25OHD is generally unnecessary but may be appropriate in patients with symptomatic vitamin D deficiency of malabsorption or where poor compliance with medication is suspected
The ‘NOS’ guidance brings together the current evidence base and pragmatic clinical guidance. Its recommendations and implementation will depend on any pre-existing local guidelines. Health care trusts with existing guidance may want to review their current practice to see if changes are needed in light of this publication. Trusts without any form of clinical guidance can use this to develop local service and tackle this highly prevalent issue.