Final answer:
Adult Rickets, or osteomalacia, is primarily caused by impaired vitamin D metabolism, leading to reduced absorption of calcium and phosphorus, necessary for bone health.
Step-by-step explanation:
The primary cause of Adult Rickets, also known as osteomalacia, is C) Impaired vitamin D metabolism. This condition arises due to the difficulty in converting vitamin D to its active form, leading to malabsorption of calcium and phosphorus, which are vital for strong bones. Factors that may contribute to this impairment include lack of exposure to sunlight, poor nutrition, certain kidney or liver diseases, and genetic disorders. Unlike children who experience rickets with more pronounced bone deformities, adults may suffer from bone pain and muscle weakness as a result of this vitamin deficiency.
Furthermore, adults can develop osteoporosis, which is related to the conditions of rickets and osteomalacia, due to calcium deficiency and continued issues with vitamin D metabolism and absorption, leading to further bone weakness and increased risk of fractures.