Vitamin D Associated Diseases and Disorders
Summary of the physiological functions of vitamin D:
🌞 Vitamin D Physiological Functions
Vitamin D’s active form (calcitriol, 1,25-dihydroxyvitamin D) works via the vitamin D receptor (VDR) to regulate many essential processes:
✅ 1️⃣ Calcium and phosphate homeostasis
- Increases intestinal absorption of calcium and phosphate
- Supports bone mineralization and remodeling
- Maintains proper serum calcium for nerve, muscle, and cardiac function
✅ 2️⃣ Bone and skeletal health
- Promotes mineralization of osteoid matrix
- Prevents rickets (children) and osteomalacia (adults)
- Works with PTH to balance bone resorption and formation
✅ 3️⃣ Muscle function
- Improves muscle strength and performance (esp. type II fibers)
- Helps prevent falls in elderly populations
✅ 4️⃣ Immune system modulation
- Enhances innate immunity (stimulates antimicrobial peptides like cathelicidin)
- Modulates adaptive immunity (reduces excessive inflammation; promotes immune tolerance)
✅ 5️⃣ Parathyroid hormone regulation
- Suppresses excessive PTH secretion when calcium is sufficient, preventing secondary hyperparathyroidism
✅ 6️⃣ Cell growth and differentiation
- Promotes cell differentiation
- Inhibits excessive proliferation in many tissues (important in tissue health and cancer prevention mechanisms)
✅ 7️⃣ Other functions
- Regulates renin production (impact on blood pressure)
- Supports insulin secretion from pancreatic β-cells
- Influences skin cell growth and hair follicle cycling
- Possible neuroprotective roles in brain development and function
💡 Key concept:
Vitamin D ensures proper mineral balance and bone strength while acting as a broad regulator of immune, muscular, and cellular processes. Its physiological role is mostly mediated through its endocrine and local paracrine actions via VDR signaling.