Final answer:
When calcium levels are decreased, phosphate levels increase.
Step-by-step explanation:
When calcium levels are decreased, phosphate levels increase.
There is a reciprocal relationship between the concentrations of calcium and phosphate ions in plasma, so a decrease in calcium levels leads to an increase in phosphate levels.
Additionally, lowered phosphorus can make parathyroid activity more apparent, which can also contribute to an increase in phosphate levels.