Calcitonin effect on calcium levels?

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Calcitonin lowers blood calcium when levels are high by slowing bone breakdown. It acts mainly on osteoclasts, inhibiting their activity so less calcium is released from bone, and it can help favor bone-building activity by osteoblasts. The overall result is a decrease in circulating calcium. This is why the option describing calcitonin as reducing calcium by inhibiting osteoclasts (and nudging bone formation) is correct. It does not promote bone resorption, so the idea of increasing calcium through breakdown is incorrect. It also does have a real effect on calcium (not none), and it doesn’t primarily increase phosphate absorption, so those statements aren’t accurate. In the body, parathyroid hormone is the main regulator that raises calcium, while calcitonin provides a secondary, calcium-lowering influence.