Anatomy, histology and physiology
The parathyroid glands are four small glands located on the back
of the thyroid gland in the neck. They are typically about the
size of a grain of rice (approximately 6 mm in length and 3-4 mm
in width) and are usually found in pairs, with two glands on
each thyroid lobe. However, the number and location of
parathyroid glands can vary among individuals, and some people
may have more or fewer than four glands. As they are small, they
cannot be seen on imaging studies such as ultrasound or CT
scans, or during autopsy, unless they are enlarged due to
disease.
There are some imaging techniques, such as sestamibi scans, where a radioactive materiale attached to sestamibi (Tc99-sestamibi) is used to visualise the glands as it is taken up by oxyphil cells in the parathyroid gland and correlates with the activity and number of mitochondria in the cell, meaning that the more hyperactive the cell is, the more potent is the uptake. However if the hyperactivity is mainly because of growth of chief cells, the glands are harder to visualise with this technique. However it is not routinely used to visualise normal parathyroid glands.
The parathyroid glands are responsible for regulating calcium levels in the blood and bone metabolism. They achieve this by producing and secreting parathyroid hormone (PTH), which increases blood calcium levels by stimulating the release of calcium from bones, increasing calcium absorption in the intestines, and reducing calcium excretion by the kidneys.
The parathyroid glands are composed of two main types of cells:
There are some imaging techniques, such as sestamibi scans, where a radioactive materiale attached to sestamibi (Tc99-sestamibi) is used to visualise the glands as it is taken up by oxyphil cells in the parathyroid gland and correlates with the activity and number of mitochondria in the cell, meaning that the more hyperactive the cell is, the more potent is the uptake. However if the hyperactivity is mainly because of growth of chief cells, the glands are harder to visualise with this technique. However it is not routinely used to visualise normal parathyroid glands.
The parathyroid glands are responsible for regulating calcium levels in the blood and bone metabolism. They achieve this by producing and secreting parathyroid hormone (PTH), which increases blood calcium levels by stimulating the release of calcium from bones, increasing calcium absorption in the intestines, and reducing calcium excretion by the kidneys.
The parathyroid glands are composed of two main types of cells:
- Chief cells: These cells are the most abundant and are responsible for producing and secreting PTH. Chief cells contain numerous secretory granules that store PTH until it is needed.
- Oxyphil cells: These cells are larger and less numerous than chief cells. They contain high levels of mitochondria which gives them their characteristic eosinophilic (pink) appearance on histological sections. Their exact function is not fully understood, but they are thought to play a role in the metabolism of PTH or in the regulation of calcium levels.
