Inferior parathyroid gland

Glandula parathyroidea inferior

Endocrine & glandsGlandsNeckLeft and right

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What it is

A lentil-sized inferior parathyroid gland embedded in the back of the thyroid lobe, one of four. Despite the name it has nothing to do with thyroid hormone; it is the body's calcium sensor.

Function

Secretes parathyroid hormone (PTH), which raises blood calcium by releasing it from bone, reducing its loss in urine and activating vitamin D.

Size

6 × 4 × 2 mm, 30–50 mg each

Clinical note

The inferior glands wander: they descend with the thymus in the embryo and may end up anywhere from the lower pole to the chest. About 5–13 % of people have a fifth gland.