Ver el código de «Vitamin D deficiency»

==Background==
*AKA: Hypovitaminosis D
*Vitamin D deficiency leads to impaired bone mineralization and diseases such as:
**[[Rickets]] in children
**[[Osteomalacia]] and [[osteoporosis]] in adults

===Metabolism and Physiology of Vitamin D===
*Gained from diet, supplements, or sunlight exposure
**Fortified foods (mainstay, eg milk, cereals), 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===
*Inadequate dietary intake, inadequate sunlight exposure
**Especially individuals with higher melanin content living in colder climates 
*Impaired vitamin D absorption
**[[Crohn's disease]], [[cystic fibrosis]], pancreatic insufficiency
*Impairment in conversion of vitamin D into active metabolites
**[[Renal Failure]], [[Liver failure]]

==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==
*[[Hypocalcemia]]
*[[Hyperparathyroidism]]
*[[Hypophosphatemia]]
*Malignancy
*[[Nonaccidental trauma]]

==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]], [[analgesia|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==
*[[Rickets]]
*[[Hypocalcemia]]
*[[Hypophosphatemia]]

{{template:vitamin deficiencies DDX}}

==External Links==

==References==
<references/>
#<Health Quality Ontario. Clinical utility of vitamin d testing: an evidence-based analysis. ''Ont Health Technol Assess Ser''. 2010;10(2): 1–93.>
#<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.>

[[Category:FEN]]