The Parathyroid Glands

The parathyroid glands are four pea-sized glands located on the thyroid gland in the neck. In man, they number four as a rule. Fewer than four were found in less than 1 per cent, but more than four in over 33 per cent. In addition, numerous minute islands of parathyroid tissue may be found scattered in the connective tissue and fat of the neck around the parathyroid glands proper, and quite distinct from them.

Occasionally one or more of the parathyroid glands embedded in the thyroid, in the thymus, or located elsewhere around this area – in most such cases, however, the glands function normally. The parathyroid glands are small brownish-red bodies, situated as a rule between the posterior borders of the lateral lobes of the thyroid gland and its capsule. They measure on an average about 6 mm. in length, and from 3 to 4 mm. in breadth, and usually present the appearance of flattened oval disks.

What are the parathyroid glands?

The parathyroid glands are small endocrine glands in the neck that produce parathyroid hormone – parathyroid glands control the amount of calcium in the body. Normally the parathyroid glands work to keep blood calcium levels in a very tightly controlled range. When the blood calcium level is too low, PTH is released to bring the calcium level back up to normal. When the calcium level is normal or gets a little too high, normal parathyroids will stop releasing PTH. Proper calcium balance is crucial to the normal functioning of the heart, nervous system, kidneys, and bones.

Where are the parathyroid glands located?

The parathyroid glands are named according to their location, into superior and inferior:

The superior parathyroid glands, usually two in number, are the more constant in position, and are situated, one on either side, at the level of the lower border of the cricoid cartilage, behind the junction of the pharynx and oesophagus. 

The inferior parathyroid glands, also usually two in number, may be applied to the lower edge of the lateral lobes, or placed at some little distance below the thyroid gland, or found in relation to one of the inferior thyroid veins.

Although their names are similar, the thyroid and parathyroid glands are entirely different glands, each producing distinct hormones with specific functions. The parathyroid glands secrete parathyroid hormone (PTH), a hormone that helps maintain the correct balance of calcium and phosphorus in the body. PTH regulates the level of calcium in the blood, release of calcium from bone, absorption of calcium in the intestine, and excretion of calcium in the urine – when the level of calcium in the blood falls too low, the parathyroid glands secrete just enough PTH to restore the blood calcium level.

If you have any questions about thyroid or parathyroid surgery, you should speak to your local doctor, who will arrange to contact your thyroid surgeon.