Question

multiple choice question
the parathyroid gland releases pth when blood calcium levels are _.
high
low

Explanation:

Parathyroid hormone (PTH) is released by the parathyroid gland to increase blood calcium levels. When blood calcium is low, PTH acts on bones (to release calcium from bone matrix), kidneys (to re - absorb more calcium and activate vitamin D which helps in intestinal calcium absorption). If blood calcium were high, hormones like calcitonin (in some species, in humans it has a minor role) would act to lower it, not PTH.

Answer:

low