Calcium and Phosphorus PDF

**Bone Composition**: Calcium and phosphorus are both critical components of hydroxyapatite, the mineral that makes up bone. The balance between these minerals is crucial for maintaining bone health. **Hormonal Regulation**: - **Parathyroid Hormone (PTH)**: - When calcium levels are low,...

**Bone Composition**: Calcium and phosphorus are both critical components of hydroxyapatite, the mineral that makes up bone. The balance between these minerals is crucial for maintaining bone health. **Hormonal Regulation**: - **Parathyroid Hormone (PTH)**: - When calcium levels are low, PTH is released, which increases blood calcium levels by stimulating: - The release of calcium from bones (osteoclast activity). - The reabsorption of calcium in the kidneys. - The conversion of vitamin D into its active form (calcitriol) enhances intestinal absorption of calcium. - PTH can also lower phosphate levels by promoting its excretion in the kidneys. - **Calcitonin**: - Lowers blood calcium levels by inhibiting osteoclast activity (thus decreasing bone resorption) and promoting calcium storage in bones. It can also increase renal excretion of phosphate. - **Vitamin D**: - Active vitamin D (calcitriol) promotes the absorption of both calcium and phosphorus in the intestines. However, it is primarily associated with calcium metabolism. **Compensatory Mechanisms**: - When serum calcium levels are low, the body often compensates by increasing phosphorus excretion to help maintain a balance, leading to a potential decrease in phosphate levels. - Conversely, elevated levels of phosphorus can lead to a decrease in calcium levels due to the body\'s regulatory mechanisms. The inverse relationship between calcium and phosphorus means that they typically have compensatory actions; however, this does not prevent both from dropping simultaneously due to a common underlying cause, such as malabsorption, vitamin D deficiency, or changes in bone metabolism due to medications. When there is inadequate absorption or availability of both minerals, such as osteomalacia or the effects of denosumab, both calcium and phosphorus levels can fall together despite their typical inverse relationship in healthy regulatory mechanisms.