Vitamin Deficiencies and Treatments Quiz

• Patients who have undergone a gastrectomy (partial or total) are at risk for cobalamin (Vitamin B12) deficiency due to impaired folate recycling.
• Symptoms of cobalamin deficiency include anemia, neuropsychiatric symptoms (irreversible CNS effects), and should be treated before symptoms appear.
• Treatment for cobalamin deficiency includes lifelong supplementation with high-dose oral B12 or intramuscular injections of cyanocobalamin.
• Pyridoxine (Vitamin B6) is a collective term for pyridoxine, pyridoxal, and pyridoxamine, all derivatives of pyridine, that function as precursors of the biologically active cofactor pyridoxal phosphate.
• Pyridoxine deficiency is rare but can occur in newborn infants, women taking oral contraceptives, and those with alcoholism. Toxicity from excessive intake results in neurologic symptoms.
• Thiamine (Vitamin B1) is essential for energy metabolism and the proper functioning of the CNS. Deficiency decreases the activity of dehydrogenase-catalyzed reactions, leading to decreased ATP production and impaired cellular function.
• Thiamine deficiency can result in diseases such as beriberi, which is characterized by peripheral neuropathy or dilated cardiomyopathy, and Wernicke-Korsakoff syndrome, which is caused by chronic alcoholism and characterized by mental confusion, gait ataxia, nystagmus, ophthalmoplegia, memory problems, and hallucinations.
• Niacin (Vitamin B3) is a cofactor in oxidation-reduction reactions that form the reduced forms NADH and NADPH. Deficiency can cause a disease called pellagra, which involves the skin, gastrointestinal tract, and CNS, progressing through the three Ds: dermatitis, diarrhea, and dementia, with death as a fourth symptom.
• Riboflavin (Vitamin B2) is a cofactor in the oxidation or reduction of substrates. Deficiency is not associated with a major human disease.
• Biotin (Vitamin B7) is a cofactor in carboxylation reactions and is widely distributed in food or supplied by intestinal bacteria. However, consumption of raw egg white can induce symptoms of biotin deficiency.
• Pantothenic acid (Vitamin B5) is a component of coenzyme A and the acyl carrier protein domain of fatty acid synthase. Deficiency is not well characterized in humans.
• Vitamin A is a fat-soluble vitamin primarily obtained from animal sources and is essential for vision, reproduction, growth, and maintenance of epithelial tissues. It also plays a role in immune function.

o The retinoids are a group of compounds that include natural forms of vitamin A (retinol and retinyl esters) and synthetic forms (retinoic acid and its derivatives), which have various functions in the body. o Retinol is absorbed from the diet as retinyl esters and is transported in chylomicrons to the liver where it is stored. o When needed, retinol is released from the liver and transported to target tissues through the bloodstream, where it regulates gene expression and affects cell differentiation. o Retinol can also be converted to retinoic acid, which binds to retinoic acid receptors (RAR) in the nucleus of target cells, leading to the regulation of gene expression and the production of specific proteins. o In the eye, retinol plays a key role in the visual cycle, specifically in the formation of rhodopsin, the visual pigment in rod cells. o Vitamin A deficiency can result in night blindness and, if left untreated, can lead to irreversible loss of visual cells and xerophthalmia, which can cause blindness. o Vitamin A toxicity, also known as hypervitaminosis A, can occur with excessive intake of vitamin A, leading to dry skin, liver damage, and central nervous system symptoms. o The D vitamins, including ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3), are a group of sterols that play a hormone-like role in the body. o Vitamin D is synthesized in the skin through the action of ultraviolet (UV) light on 7-dehydrocholesterol, and is also found in dietary sources. o The active form of vitamin D, 1,25-dihydroxycholecalciferol, binds to intracellular receptor proteins and interacts with response elements in the nucleus of target cells, regulating the levels of calcium and phosphorus. o Vitamin D deficiency can result in a condition called rickets, which is characterized by weak and soft bones, and can lead to a condition called osteomalacia in adults. o Vitamin K plays a role in the posttranslational modification of proteins, primarily those involved in blood clotting.