Final answer:
Parathyroid hormone (PTH) is the best-known nutrient and hormone involved in regulating blood calcium and phosphorus levels to maintain bone integrity.
Step-by-step explanation:
The best-known member of a large cast of nutrients and hormones that interact to regulate blood calcium and phosphorus levels, thereby maintaining bone integrity, is parathyroid hormone (PTH). PTH, along with dihydroxyvitamin D (calcitriol), and calcitonin, are crucial in controlling blood levels of calcium and phosphate. These hormones ensure proper bone health, muscle contraction, nerve impulse transmission, and many other biological processes by regulating calcium absorption and its reabsorption in the kidneys, as well as the activation of vitamin D in the kidney which aids intestinal calcium ion absorption.