ATI Pathophysiology Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

Calcitonin is the hormone produced by the thyroid gland that plays a significant role in calcium metabolism. It is released in response to high levels of serum calcium and functions primarily to lower blood calcium levels. Calcitonin achieves this by inhibiting osteoclast activity, which reduces bone resorption (the process where bone is broken down and calcium is released into the bloodstream) and promoting the deposition of calcium into bone. It also reduces renal tubular reabsorption of calcium, which increases calcium excretion through urine.

In contrast, other hormones mentioned do not primarily regulate calcium metabolism. Parathyroid hormone, produced by the parathyroid glands, actually raises blood calcium levels by stimulating osteoclasts, increasing intestinal absorption of calcium, and decreasing renal excretion of calcium. Cortisol, a glucocorticoid, has multiple functions, including anti-inflammatory effects but is not directly involved in calcium regulation. Epinephrine, mainly involved in the body's fight-or-flight response, also does not play a significant role in calcium regulation. Thus, calcitonin is correctly identified as the hormone specifically active in calcium metabolism produced by the thyroid gland.