Hey picked this up form wiki for you, a little info on Vitamin D deficiency:
Deficiency
Vitamin D deficiency can result from: inadequate intake coupled with inadequate sunlight exposure, disorders that limit its absorption, conditions that impair conversion of vitamin D into active metabolites, such as liver or kidney disorders, or, rarely, by a number of hereditary disorders. Deficiency results in impaired bone mineralization, and leads to bone softening diseases, rickets in children and osteomalacia in adults, and contributes to osteoporosis.
Diseases caused by deficiency
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Vitamin D deficiency is known to cause several bone diseases including:
Rickets, a childhood disease characterized by impeded growth, and deformity, of the long bones. The earliest sign of subclinical vitamin D deficiency is Craniotabes, abnormal softening or thinning of the skull.
Osteomalacia, a bone-thinning disorder that occurs exclusively in adults and is characterized by proximal muscle weakness and bone fragility.
Osteoporosis, a condition characterized by reduced bone mineral density and increased bone fragility.