Vitamin D Deficiency and Replacement on Pulmonary and Endocrine Function in SCI

Part 1: Screening for Vitamin D Deficiency Inclusion Criteria: * Between the ages of 18 and 75, * Chronic (\>1 year) SCI; tetraplegia (C3-8), paraplegia, (T1-6) Exclusion Criteria: * Acute illness * Acute drug or alcohol use * Lack of mental capacity to give informed consent, * Pregnancy, * Currently receiving Vitamin D supplementation. Part 2A: Vitamin D and Pulmonary Function Inclusion Criteria: * Between the ages of 18 and 75, * Chronic SCI (\>1 year, C3-T6) * Vitamin D deficiency as defined as a value \<20 ng/ml. Exclusion Criteria: * Smoking, active or history of smoking during life time, * Any history of blast injuries to the chest, * Active respiratory disease, * Pregnancy, * Lack of mental capacity to give informed consent. * Recent (within 3 months) respiratory infection. * Receiving medications known to alter airway caliber. * Acute drug or alcohol use, * Currently receiving Vitamin D supplementation \> 1000 units/day. Part 2B: Vitamin D, Carbohydrate Metabolism, and Insulin Resistance Inclusion Criteria: * Between the ages of 18 and 75, * Chronic SCI (\>1 year, C3-T6) * Vitamin D deficiency as defined as a value \<20 ng/ml, * Insulin Resistance (IR), Impaired glucose tolerance (IGT), and/or Diabetes Mellitus (DM). Exclusion Criteria: * Pregnancy, * Problems with the kidneys, * Lack of mental capacity to give informed consent, * Acute drug or alcohol use, * Currently receiving Vitamin D supplementation \> 1000 units/day.