Parathyroid Gland Overview: Parathyroid Function, Parathyroid Location, Parathyroid Gland Disease.
Hyperparathyroidism, parathyroid surgery, and complications of high blood calcium. Parathyroid glands are located in the neck behind the thyroid where they . They have no relationship except they are neighbors. The parathyroid is located near your thyroid; however, their functions close to the thyroid gland anatomically, they have no related function. VOL: , ISSUE: 22, PAGE NO: 26 Brendan Docherty, MSc, PGCE, RN is clinical stream manager, cardiology and critical care, South Eastern Sydney and .
In this issue, we move down the body to examine the five endocrine glands found in the neck: As it turns out, malfunctions in these glands are not that uncommon, can produce serious problems such as over excitement of the muscle and nervous systems, bony demineralization, high calcium levels, duodenal ulcers, kidney stones, and behavioral disorders.
And if left unchecked, they can kill you. Fortunately, there are things you can do to minimize the chances of these problems occurring in the first place, or relieving them through alternative means if you get them.
With that in mind, let's begin by looking at the thyroid gland. Thyroid overview In essence, the thyroid gland is the thermostat of the body. It is one of the largest endocrine glands in the body and specifically controls how quickly the body uses energy, how it makes proteins, and the body's sensitivity to other hormones.
The function of the thyroid gland is to take iodine and convert it into thyroid hormones -- primarily, thyroxine T4 and triiodothyronine T3. Normal thyroid cells accumulate and retain iodide far, far more efficiently than do any other cells in the body.
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Most cells don't absorb iodine at all, but some, including thyroid cancer cells and breast epithelial cells, can to a limited degree. Thyroid cells combine iodine and the amino acid tyrosine as bound to thyroglobulin to make T3 and T4.
We will cover this process in more detail a little later. T3 and T4 are then released into the bloodstream and transported throughout the body, where they control metabolism i. Every cell in the body depends upon thyroid hormones for regulation of their metabolism.
Anatomically speaking, the thyroid is a butterfly shaped gland two larger lobes connected by a narrower isthmus located between the Adam's apple and the clavicle. When viewed from the front of the body, the thyroid totally covers the trachea. Nevertheless, a normal thyroid gland cannot be felt externally. If a doctor can "see" it or "feel" it when touching the neck with his fingers, it's enlarged.
Under normal circumstances, it's soft and flat. Not surprisingly for such an important organ, it is richly serviced by multiple arteries and veins, which makes surgery on the thyroid that much more difficult. In addition, surgeons face further complications since the nerves that service the vocal cords run right next to the arteries that provide blood to the thyroid. Bottom line is that the thyroid is intricately entwined with key nerves and blood vessels.
And it's not just surgery on the thyroid that presents problems. Tracheotomies, for example, must be performed either above or below the thyroid gland. It is also the main reason doctors prefer to "kill" the thyroid with radioactive iodine rather than remove it surgically a procedure we will talk more about later. At the micro level, the thyroid is primarily comprised of spheres called follicles.
- Thyroid and Parathyroid Disease
- An Overview of the Parathyroid
- Parathyroid Gland Introduction
The follicles themselves are primarily composed of two types of cells: On the outside circumference of the follicles are the cuboidal follicular cells.
The follicular cells produce two iodine based compounds, thyroxine tetraiodothyronine, also known as T4 and triiodothyronine also known as T3.
On the inside circumference, or lumen of the follicle, is a brush border composed of hairlike extensions not visible in the slide below. This allows for the easy deposit and removal of key hormonal components into the follicular lumen see slide below as required for production of T3 and T4.
The parafollicular cells C cells sit scattered about the outer edge of the follicles on top of the follicular cells and produce calcitonin, a minor regulator of calcium in the body. Thyroid hormones When talking about thyroid hormones, we're actually talking about four bio-chemicals: Thyroglobulin is a protein not a hormone produced by the thyroid. It is synthesized from amino acids and iodide and stored in the follicular lumen as colloid and used entirely within the thyroid gland in the production of the thyroid hormones.
T3 triiodothyronine affects almost every physiological process in the body, including growth and development, metabolism, body temperature, and heart rate. As a side note, the 3 in its name refers to the fact that it contains 3 iodine atoms. T4 thyroxine, AKA tetraiodothyronine is the prohormone from which the body extracts T3. It is synthesized from residues of the amino acid tyrosine, found in thyroglobulin. Every cell in the body depends upon the thyroid hormones T3 and T4 for regulation of their metabolism.
However, T3 is about four times "stronger" than T4. T4 is converted to T3 in body cells. This allows the body to fine tune the metabolic regulating capabilities of T3 and T4. As with T3, the 4 in T4's name refers to the fact that T4 contains 4 iodine atoms. Calcitonin is produced in the parafollicular cells and regulates calcium levels in the blood to a minor degreealong with the parathyroid glands the main regulator.
It lowers blood calcium and phosphorus by decreasing the rate of re-absorption of these minerals from bone. As we discussed previously, thyroid chemistry is an iodine-based chemistry; iodine must be ingested because it can't be manufactured in the body; it is an element, not a compound.
Any iodine you ingest is trapped exclusively by cells in the thyroid to be used for manufacturing thyroglobulin and, ultimately, T3 and T4. This fact is exploited by endocrinologists when it comes to treating several thyroid disorders. We will talk more about this later.
Thyroid and Parathyroid Disease - UCLA Endocrine Center, Los Angeles, CA
If iodine is not present in sufficient amounts, the body will develop a benign goiter enlargement of the thyroid over time. It is common in areas where iodine does not naturally occur in food. In the early 's, Western countries began adding iodine to salt to combat this problem. And it worked, in the sense that goiters are now uncommon in the Western world. For this reason, it is our opinion that every patient being evaluated for parathyroid disease should undergo ultrasound evaluation of the thyroid and parathyroid glands prior to surgery.
Ideally this should be done by the surgeon during the initial consultation, or planning phase for surgery. This is our standard practice at UCLA Endocrine Surgery, and it is rapidly gaining wide acceptance among other expert centers see References. An important study conducted at the University of Wisconsin showed that almost half of patients being evaluated for primary hyperparathyroidism had suspicious thyroid findings on ultrasound.
Thyroid cancer was discovered in several patients, allowing for appropriate treatment of both thyroid and parathyroid disease with a single operation. Experts at the Cleveland Clinic conducted a similar study in which they found that routine pre-operative ultrasound evaluation actually reduced the need for unnecessary thyroid surgery. Ultrasound allows thyroid cancer to be detected in a small but significant number of patients being evaluated for parathyroid disease primary hyperparathyroidism.
Those patients are at risk for inadequate initial surgery, i. Given how frequently parathyroid disease and thyroid cancer occur together, it is statistically inevitable that solely operating on the parathyroids without ultrasound evaluation of the thyroid will lead to thyroid cancers being left behind untreated.
On the other hand, many thyroid nodules are benign and do not require surgery. Those patients are at risk for excessive surgery, for example if their surgeon discovers a thyroid nodule at the time of surgery and decides to remove the nodule or biopsy it surgically, which is often not the right thing to do Why?
Patients need just the right amount of surgery. Ultrasound permits this in thyroid and parathyroid disease by creating a roadmap for the operation. It is common for many surgeons to offer to inspect or evaluate the thyroid during parathyroid surgery.
We do not believe this represents best clinical practice, for several reasons. Specimen from a patient with both thyroid and parathyroid disease.
This patient's thyroid nodule was determined to be benign. Why ultrasound evaluation of the thyroid prior to parathyroid surgery is preferable to visual inspection of the thyroid during parathyroid surgery Visual inspection of the thyroid during parathyroid surgery may only reveal problems on the surface of the thyroid, as opposed to ultrasound which can penetrate into the deep substance of the thyroid.
This is not considered standard of care for suspicious thyroid nodules. Suspicious thyroid nodules are best treated with thyroid lobectomy hemithyroidectomy or removal of half of the thyroid gland. Lobectomy permits pathologic microscopic evaluation of the boundary between the suspicious nodule and the adjacent normal thyroid tissue, which often reveals the deciding factor between which nodules are malignant cancerous and which nodules are benign, that is, the presence or absence of invasion.
The thyroid hormone, parathyroid hormone and vitamin D associated hypertension
The presence of thyroid cancer is best detected by pre-operative ultrasound-guided fine-needle aspiration FNA of thyroid nodules. This is widely accepted as best practice.
Having this knowledge in advance of surgery permits careful planning of the operation and mobilization of any additional resources necessary for a more complex cancer operation. Thyroid cancer surgery generally involves a total thyroidectomy and often a lymph node dissection.
It is best for the surgeon to be prepared for this ahead of time, as an improvised thyroid cancer operation is unlikely to yield the best outcome for the patient.
The thyroid hormone, parathyroid hormone and vitamin D associated hypertension
Ultrasound affords the patient the best chance of having a single, definitive operation. We have previously discussed the potential for leaving thyroid cancers behind. Indeed, we see patients for re-do thyroid surgery every week at UCLA and sometimes we perform multiple re-do thyroid operations in a single day.