Question

if blood calcium levels drop below 8.5 mg/dl which hormone is likely to be activated?
calcitonin
calcitriol
estrogen
parathyroid hormone
both calcitriol and parathyroid hormone

Explanation:

When blood calcium levels drop below normal (8.5 - 10.5 mg/dL), parathyroid hormone (PTH) is released by the parathyroid glands. PTH acts to increase blood - calcium levels by promoting calcium release from bones, enhancing calcium reabsorption in the kidneys, and stimulating the activation of vitamin D (calcitriol) for increased intestinal calcium absorption. Calcitriol also helps increase blood calcium levels when activated by PTH. Calcitonin lowers blood calcium levels when they are too high. Estrogen is mainly involved in female reproductive and other physiological functions and not the primary regulator of low - calcium situations.

Answer:

E. both calcitriol and parathyroid hormone