Medicine The most impoant regulator of serum 1,25 (OH)2 vitamin D concentration is A Serum calcium B Serum magnesium C Serum 25 (OH) vitamin D D Parathyroid hormone 💡 Explanation The most impoant regulator of serum 1,25 (OH)2 vitamin D concentration is ✓ Correct Answer: D. Parathyroid hormone