Blood calcium plays a role in the processes of blood clot formation, muscle contraction and signal conduction in neurons. Negative feedback mechanisms regulate the release of the paired hormones that maintain the blood calcium levels. Which of the following statements correctly describes this regulatory process?

1. The pituitary gland releases calcium ions when blood calcium levels fall below the set
point.
2. Calcitonin, released by the adrenal gland stimulates the deposition of calcium from
bones into the blood stream when blood calcium levels are high.
3. T4, secreted by the thyroid gland stimulates the release of calcium from the
parathyroid gland when blood calcium levels fall below the set point.
4. Parathyroid glands released PTH which stimulates the release of calcium from bones
when the blood calcium levels are lower than the set point