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Parathyroid

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What is a parathyroid gland and when is it a problem

A parathyroid gland is a tiny cluster of cells that produces parathyroid hormone, which circulates in the bloodstream and causes the calcium concentration in the blood to increase. Keeping the concentration of calcium in the blood within a normal range is necessary for many organ systems to function, and when the calcium level decreases, the parathyroid glands respond by producing more parathyroid hormone, which maintains homeostasis. Similarly, when blood calcium is high, the parathyroid glands decrease production of parathyroid hormone, and the calcium level trends back down. Most people have four parathyroid glands (although some have one or two fewer or up to several more), yet only one half of one gland is required to perform the necessary function of maintaining calcium levels.

The most common problem with a parathyroid glands is that they tend to develop into a benign tumor that produces excess parathyroid hormone and does not decrease production when the blood calcium level is high. This can cause symptoms such as fatigue, depression, joint aches, abdominal problems, and urinary stones. Since some of the calcium used to keep the blood levels high comes from the bones, over time, the bones get weaker, sometimes leading to osteopenia and fracture.

Types of hyperparathyroidism

When one or more parathyroid glands become a tumor, producing excess parathyroid hormone, this is called primary hyperparathyroidism. This is different from secondary hyperparathyroidism, which is when kidney disease causes wasting of calcium in the urine, causing parathyroid glands to work extra just to keep the blood calcium normal. Like a muscle getting exercised, these parathyroid glands (all of them) tend to become large, but they are still doing their job correctly. Tertiary hyperparathyroidism is when after a long period of secondary hyperparathyroidism, the kidney disease is resolved, but the parathyroid glands fail to slow down their production of parathyroid hormone, Primary and tertiary hyperparathyroidism are diseases treatable with parathyroid surgery, whereas secondary hyperparathyroidism is a problem with the kidneys.

hypoparathyroidism

Having inadequate amounts of parathyroid hormone production is hypoparathyroidism. This commonly occurs in a temporary fashion after surgery on or near the parathyroids because these glands are easily “stunned.” Permanent hypoparathyroidism, however, very rarely occurs unless surgery has removed or cut off the blood supply of the parathyroids. Only one half of one parathyroid gland is needed for adequate parathyroid hormone production, but less than that can lead to permanent hypoparathyroidism, which is treated with daily supplemental vitamin D and calcium long-term.

evaluation of hyperparathyroidism

Most cases of primary hyperparathyroidism are identified through routine blood tests, in which calcium is elevated, parathyroid hormone is elevated, and kidney function is normal. A familial variation called Familial Hypocalciuric Hypercalcemia (FHH)must then be ruled out, and then the diagnosis is made. (FHH is when the normal set point for calcium in an individual and their blood relatives is higher than normal. This does not need surgery, and can usually be identified by asking if other family members have had unsuccessful parathyroid surgery. If the answer is yes, FHH is suspected. A 24 hour urine collection is a more definitive way to evaluate for FHH.) Other times, a patient may have urinary stones that lead to some investigation, uncovering hyperparathyroidism or enlarged and active parathyroid gland(s) may be incidentally found on imaging performed for some other purpose. In 99% of primary hyperparathyroidism cases, the tumor(s) is benign, and the 1% of malignant cases (parathyroid carcinoma), extremely high calcium and parathyroid hormone are clues and the diagnosis is confirmed by pathologic examination of the surgical specimen.

Variable anatomic location of parathyroid glands

From: Anatomy, Head and Neck, Parathyroid, Ectopic Glands

StatPearls [Internet].

Treasure Island (FL): StatPearls Publishing; 2023 Jan-.

Typically, there are four parathyroid glands, with two situated on each side of the thyroid gland. However, it is worth noting that the anatomic location of parathyroid glands can vary among individuals. In some cases, these glands may be found in ectopic or abnormal locations, such as in the thymus, within the thyroid gland itself, or even in the chest or mediastinum. Ectopic parathyroid glands can present challenges in their identification and surgical treatment due to their atypical positions. Therefore, a combination of pre-operative localizing studies and the surgeon’s awareness of the variable anatomic locations of parathyroid glands help minimize the risk of not finding a parathyroid gland.

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