Final answer:
Hyperparathyroidism is the condition of increased PTH secretion by parathyroid glands, characterized by high blood calcium and low serum phosphate, often resulting from parathyroid tumors.
Step-by-step explanation:
The increased secretion of PTH (parathyroid hormone) by the parathyroid glands is known as hyperparathyroidism. This condition is characterized by elevated levels of calcium in the blood, known as hypercalcemia, decreased urinary calcium, and low levels of phosphate in the serum. Hyperparathyroidism often results from tumors in the parathyroid glands, leading to bone destruction and kidney stones. PTH plays a crucial role in managing calcium metabolism by stimulating osteoclasts to break down bone, enhancing calcium reabsorption in the kidneys, and converting vitamin D into its active form, calcitriol.