How do hormones from the thyroid and parathyroid regulate the calcium concentration of the blood?

A Both parathroid hormone and the three thyroid hormones function to regulate blood calcium levels

B Thyroxine and triiodothyronine together regulate calcium levels, as needs dictate

C Parathyroid hormone lowers blood calcium; calcitonin raises blood calcium

D Calcitonin lowers blood calcium; parathyroid hormone raises blood calcium

Answer & Explanation
Answer: Calcitonin lowers blood calcium; parathyroid hormone raises blood calcium