What will high calcium levels cause in terms of hormone levels?

High calcium levels lead to a decrease in parathyroid hormone (PTH) levels. The parathyroid glands monitor serum calcium concentrations, and when calcium levels rise above normal, these glands respond by reducing the secretion of PTH. PTH is responsible for increasing blood calcium levels by promoting the release of calcium from bones, increasing calcium reabsorption in the kidneys, and enhancing intestinal absorption of calcium through its effects on vitamin D.

Conversely, when calcium levels are high, there is no need for PTH to elevate them further, so its secretion is inhibited. This negative feedback mechanism ensures calcium homeostasis is maintained in the body. Additionally, while high calcium levels can also influence calcitonin release—typically increasing it to lower calcium levels—this is not a direct action related specifically to PTH.

Understanding this relationship is crucial in the context of hypercalcemia and how the endocrine system responds to changes in calcium levels.