Pathophysiology
Clinical meaning
Vitamins are organic micronutrients essential for enzymatic reactions, cellular metabolism, and tissue maintenance. Fat-soluble vitamins (A, D, E, K) are stored in adipose tissue and the liver, while water-soluble vitamins (B complex, C) require regular dietary intake. Vitamin A deficiency impairs rhodopsin synthesis causing night blindness and weakens epithelial barriers. Vitamin D deficiency disrupts calcium-phosphorus homeostasis leading to rickets in children and osteomalacia in adults. Vitamin B12 deficiency causes megaloblastic anemia and peripheral neuropathy due to impaired DNA synthesis and myelin maintenance. Vitamin C deficiency (scurvy) weakens collagen synthesis causing bleeding gums, petechiae, and poor wound healing. Thiamine (B1) deficiency causes beriberi and Wernicke encephalopathy through impaired glucose metabolism in neural tissue.