Describe how blood calcium levels are maintained, including the hormones involved and how they are regulated.

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durbanville eNotes educator| Certified Educator

Good health depends on various factors and is dependent on the body's ability to produce, process and utilize all available minerals and other essential elements. Minerals are critical for good health, and with Sodium, Magnesium and Potassium among them, the most common mineral is Calcium. It is well-known for its benefits to bone health but it is also crucial in blood flow and muscle maintenance.

The blood carries a very small percentage of Calcium but it is no less important and there are three main hormones which are responsible for maintaining blood calcium levels. They are Vitamin D (the 'sunshine' vitamin) which acts as a hormone, parathyroid hormone (PTH) (found at the back of the thyroid gland) and Calcitonin.

The bones are responsible for calcium storage and play a critical role in regulating blood calcium levels; otherwise the bones are deprived of it when a deficiency means that it has to be directed elsewhere into the blood, as controlled by the parathyroid hormone (PTH) in the absence of sufficient Vitamin D. Cells, known as osteoclasts break down bones so that Calcium is released into the bloodstream. Of course, the body strives to ensure homeostasis, and when blood calcium levels drop, the parathyroid hormone also alerts the kidneys which contribute to the maintenance of calcium levels by excreting it. Less is then excreted in the urine.

PTH is also responsible for the kidneys producing the active form of Vitamin D which then leads to an increase in calcium absorption from the gut. A deficiency in Vitamin D will lead to low blood calcium levels as Calcium is not adequately absorbed and is then leached from the bones. Just as PTH increases blood calcium levels so Calcitonin reduces them in an effort to slow the breakdown of bone. 

justaguide eNotes educator| Certified Educator

Blood calcium levels are maintained at appropriate levels by the parathyroid hormones, vitamin D and a hormone known as calcitonin.

The parathyroid hormones and vitamin D are responsible for the increase of calcium levels in the blood. These hormones acting directly and by regulating the Vitamin D levels in the blood aid in calcium absorption in the small intestine, prevent loss of calcium from the body through the kidneys and regulate the excretion of phosphate in the body as an increase in phosphates leads to a fall in calcium levels

Calcitonin on the other hand is responsible for reducing calcium levels by increasing the outflow of calcium from the body through the kidneys and preventing calcium from entering the body from the bones.