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HealthVetted
Endocrine System

Parathyroid Glands

Four tiny glands behind the thyroid that secrete parathyroid hormone, the body's main regulator of blood calcium.

Reviewed by HealthVetted EditorialLast reviewed: May 30, 2026

Reviewed & updated

The parathyroid glands are the body's primary controllers of blood calcium, a mineral essential for nerve signaling, muscle contraction, blood clotting, and bone strength. Despite their tiny size, they are indispensable.

Structure and Location

Most people have four parathyroid glands, each about the size of a grain of rice, embedded on the posterior (back) surface of the thyroid gland in the neck. They are typically arranged as two superior and two inferior glands, although the number and location can vary. The superior glands derive embryologically from the fourth pharyngeal pouch and the inferior glands from the third pharyngeal pouch, which explains why inferior glands occasionally migrate into the chest.

Microscopically, the glands contain two main cell types: chief cells, which are smaller, more numerous, and responsible for producing parathyroid hormone (PTH), and oxyphil cells, which are larger and whose function is less clear.

Key Functions

The parathyroid glands secrete parathyroid hormone (PTH) in response to low blood calcium, detected by calcium-sensing receptors on the chief cells. PTH raises blood calcium through three actions: stimulating bone to release calcium, increasing calcium reabsorption in the kidneys, and activating vitamin D so the intestines absorb more dietary calcium. As calcium and vitamin D levels rise, they feed back to suppress further PTH release, keeping calcium within a narrow, tightly regulated range. PTH works in opposition to calcitonin from the thyroid.

Clinical Relevance

Primary hyperparathyroidism, often from a benign adenoma, causes excess PTH and high blood calcium, which can lead to kidney stones, bone thinning, fatigue, and abdominal complaints ('stones, bones, groans'). Hypoparathyroidism, sometimes an accidental complication of thyroid surgery, causes low calcium with muscle cramps, tingling, and tetany. Because the glands are small and variably located, they are a key consideration during neck surgery.

*This content is educational and not a substitute for professional medical advice.*

Sources & references

  1. Anatomy, Head and Neck, Parathyroid - StatPearls - NCBI Bookshelf. StatPearls / NCBI Bookshelf (2023)
  2. Physiology, Parathyroid - StatPearls - NCBI Bookshelf. StatPearls / NCBI Bookshelf (2023)
  3. Histology, Parathyroid Gland - StatPearls - NCBI Bookshelf. StatPearls / NCBI Bookshelf (2023)
  4. The Parathyroid Glands - Anatomy and Physiology II (Lumen/OpenStax). Lumen Learning / OpenStax (2022)
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