Vitamin D deficiency

Background

  • AKA: Hypovitaminosis D
  • Vitamin D deficiency leads to impaired bone mineralization and diseases such as:

Metabolism and Physiology of Vitamin D

  • Gained from diet, supplements, or sunlight exposure
    • Fortified foods (mainstay), supplements, fatty fish, egg yolks, fish liver oil, and some mushrooms
    • Synthesis of vitamin D occurs in the skin through exposure to ultraviolet B radiation from sunlight
  • Hydroxylated in liver→ 25-hydroxyvitamin D, which is further hydroxylated in kidney or extrarenally→ 1,25-dihydroxyvitamin D (active form)
    • Second hydroxylation regulated by PTH, serum calcium, and phosphorus levels
  • Vitamin D acts to:
    • Stimulate intestinal calcium absorption
    • Maintain adequate phosphate levels for bone development
    • Regulate cell growth proliferation and apoptosis
    • Modulate immune function and inflammation reduction

Etiology of Vitamin D Deficiency

Clinical Features

  • Bone pain
  • Muscle weakness
  • Brittle bones
    • Rickets in children
      • Soft bones, skeletal deformities
      • Craniotabe: abnormal softening or thinning of the skull
    • Osteomalacia and Osteoporosis in adults leading to increased risk of fractures
  • Associated with advancement of cancers, particularly of breast, colon, ovarian, and prostate

Differential Diagnosis

Evaluation

  • Assess for fractures, if indicated
  • BMP, Mg/Phos, serum calcium
  • Vitamin D assessed by measuring serum concentration of 25-hydroxyvitamin D (precursor to hormonally active 1,25-dihydroxyvitamin D)
    • Normal range: 75-250 nmol/L
    • Insufficiency: 25-75 nmol/L
    • Deficiency: <25 nmol/L
    • Screening adults not at risk and without symptoms not recommended

Management

  • Treat complications (e.g. fractures, pain)
  • Supplemental vitamin D
    • Initial high-dosage treatment phase: 1,000 IU cholecalciferol per 10 nmol/L required serum increase given daily for 2-3 months
    • Maintenance: 400 IU daily
      • Double dosage for premature infants, infants/children with dark pigmentation, children with limited sun exposure, and obese patients
    • Some populations may require higher dosing (i.e. parathyroid disease, chronic liver disease, renal failure, and malabsorption disorders)

See Also

External Links

References

  1. <Health Quality Ontario. Clinical utility of vitamin d testing: an evidence-based analysis. Ont Health Technol Assess Ser. 2010;10(2): 1–93.>
  2. <Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, Heaney RP, Murad H, and Weaver CM. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society Clinical Practice Guideline. "J Clin Endocrinol Metab". Jul 2011; 96(7): 1911–1930.>