The role of Vitamin D treatment

Vitamin D through its active form (1,25-dihydroxyvitamin D) is essential for intestinal Ca absorption and plays a central role in maintaining Ca homeostasis and skeletal integrity¹

In vitamin D deficiency there is a decrease in the concentration of 25(OH) vitamin D (25-hydroxy vitamin D) and an increase of varying degrees in the parathyroid hormone (PTH) level²

The increased serum PTH stimulates bone turnover, leading to bone loss³

In periods of protracted vitamin D deficiency, bone loss is increased and this may lead to osteoporosis³

“There is widespread acknowledgement of the presence of vitamin D deficiency in the community and the pressing need to address this deficiency¹“
Prof Kevin Cashman, UCC, commenting on the results of the Irish NANS Study 2013.

• The North American Institute of Medicine (IOM)’s DRI Committee for Ca and vitamin D proposes a serum 25(OH)D concentration of 50nmol/L that would meet the needs of 97.5% of normal healthy persons¹

• In agreement with the Scientific Advisory Committee on Nutrition (SACN)²  report, the Royal Osteoporosis Society (ROS)³ in the UK proposes vitamin D thresholds as follows:Plasma 25 (OH) D < 25 nmol/L is deficientPlasma 25 (OH) D of 25 – 50 nmol/L may be inadequate in some peoplePlasma 25 (OH) D > 50 nmol/L is sufficient for almost the whole population

• The Endocrine Society Clinical Practice Guideline defines vitamin D deficiency as 25(OH)D below 50nmol/L and vitamin D insufficiency below the range of 52.5-72.5nmol/L⁴
• The American Geriatrics Society Consensus Statement on Vitamin D for the Prevention of Falls and their Consequences recommends that a serum 25(OH)D concentration of 75nmol/L should be a minimum goal to achieve in older adults, particularly in frail adults who are at greater risk of falls, injuries and fractures⁵
• The guideline statement from the Scientific Advisory Council of Osteoporosis Canada states that the optimal level of serum 25(OH)D for musculoskeletal benefits is >75nmol/L⁶
• The American Academy of Paediatrics (AAP) states that serum concentrations of 25(OH)D in infants and children should be at least 50nmol/L⁷ The Canadian Paediatric Society defines deficiency as serum 25(OH)D levels <25 nmol/l, insufficiency as 25-75nmol/L but highlights a range of 75-225nmol/L as optimal for parathyroid hormone production, minimisation of resorption from bone and stabilisation of intestinal calcium absorption⁸
• The Evidence-Based Recommendations from the Cystic Fibrosis Foundation, published in JCEM 2012, recommend a minimum serum 25(OH)D level of 75nmol/L for people with cystic fibrosis⁹

Osteomalacia and vitamin D deficiency treatment

• In young children, who have little mineral in their skeleton, vitamin D deficiency results in a variety of skeletal deformities classically known as rickets⁵
• In adults, the epiphyseal plates are closed and there is enough mineral in the skeleton to prevent skeletal deformities so that this mineralisation defect, known as osteomalacia, often goes undetected⁵
• However osteomalacia causes a decrease in Bone Mineral Density (BMD) and is associated with isolated or generalised aches and pains in bones and muscles⁵

Osteomalacia is softening or weakening of the bones due to a lack of vitamin D or due to a problem with the body’s ability to break down and absorb vitamin D.

• Vitamin D deficiency causes muscle weakness
• Affected children have difficulty standing and walking
• The elderly have increasing sway and more frequent falls, thereby increasing their risk of fracture⁵

The pathophysiologic pathways from vitamin D deficiency to osteoporosis, osteomalacia, falls and fractures:³