Final answer:
The parathyroid glands secrete parathyroid hormone (PTH) in response to low blood calcium levels, playing a crucial role in regulating calcium ion levels in the plasma.
Explanation:
Parathyroid glands are small glands located on the posterior aspect of the thyroid gland that secrete parathyroid hormone (PTH) in response to low levels of calcium in the plasma. PTH plays a crucial role in increasing calcium ion levels in the plasma through various mechanisms.
The pituitary gland does not secrete hormones in response to hypocalcemia, unlike the parathyroid glands. Therefore, the correct answer to the question would be the parathyroid glands.
When blood calcium levels are low, the parathyroid glands release PTH, which then acts to mobilize calcium from bones, enhance calcium absorption from the intestines, and increase calcium reabsorption in the kidneys.
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