Bone metabolism

Bone Metabolism
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Synonyms	Bone remodeling, Bone turnover
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Bone metabolism, also known as bone remodeling or bone turnover, is the continuous process through which old bone tissue is replaced by new bone tissue. This process is essential for the maintenance of skeletal strength and mineral homeostasis. Bone metabolism involves the coordinated actions of two main cell types: osteoblasts, which are responsible for bone formation, and osteoclasts, which are responsible for bone resorption.

Physiology of Bone Metabolism

Bone metabolism is a dynamic process that ensures bone strength and the regulation of mineral balance in the body, including calcium and phosphorus. The process is regulated by a variety of hormones, vitamins (notably Vitamin D), and cytokines.

Bone Formation

Bone formation is primarily carried out by osteoblasts, which originate from stem cells in the bone marrow. These cells produce collagen and other proteins that form the organic matrix of bone, which is later mineralized through the deposition of calcium and phosphate.

Bone Resorption

Bone resorption is the process by which osteoclasts break down the bone tissue, releasing minerals back into the bloodstream. This process is crucial for the repair of micro-damages in bone and for the release of minerals required for other bodily functions.

Regulation

The balance between bone formation and resorption is regulated by several factors:

• Parathyroid hormone (PTH) increases bone resorption to elevate serum calcium levels.
• Calcitonin, produced by the thyroid gland, decreases bone resorption.
• Sex hormones, such as estrogen and testosterone, which promote bone formation and decrease resorption.
• Mechanical stress and physical exercise also stimulate bone formation.

Disorders of Bone Metabolism

Disorders of bone metabolism can lead to weakened bones and conditions such as osteoporosis, osteopetrosis, and Paget's disease of bone. These conditions can significantly affect an individual's quality of life by increasing the risk of fractures and other complications.

Osteoporosis

Osteoporosis is characterized by low bone mass and structural deterioration of bone tissue, leading to bone fragility and an increased risk of fractures. It is often associated with aging and is more common in females than in males.

Paget's Disease of Bone

Paget's disease of bone is a chronic disorder that can result in enlarged and misshapen bones. The excessive breakdown and formation of bone tissue can cause bone to weaken, resulting in pain, misshapen bones, and fractures.

Treatment and Management

Treatment of bone metabolism disorders typically focuses on slowing the rate of bone loss or boosting the rate of bone formation. Common treatments include:

• Calcium and Vitamin D supplements
• Bisphosphonates
• Hormone replacement therapy

See Also

• Bone density
• Bone disease
• Endocrinology