Thyroid Gland Overview – Role in Regulating Your Metabolism

The thyroid gland maybe just a small part of the body, but this impacts almost all the metabolic processes of the body.

The thyroid gland

Thyroid gland is derived from the Latin word glandula thyreoidea. The word glandula means gland and thyreoidea means shield-like and/or shield-shaped. The origin of thyreoidea can be traced back from the Ancient Greeks.

The thyroid gland is commonly called as thyroid. It is a butterfly-shaped organ located in the anterior base of the neck.

It is located just below the Adam’s apple/laryngeal prominence. The thyroid gland is one of the largest endocrine glands in the human body.

It surrounds the larynx and underlying trachea. The thyroid extends up to the esophagus and carotid sheath.

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Pregnancy week by week

The attachment of the thyroid to the trachea is the reason why it creates a movement whenever a person swallows. This gland stretches from the oblique line of the thyroid cartilage up to the 5th or 6th tracheal ring.

The thyroid gland weighs about 2-3 grams in babies and 18-60 grams in adults. But for women, the weight increases during pregnancy.

The entire gland is covered with a thin fibrous sheath (capsula glandulae thyreoideae). The sheath is composed of both internal and external layers.

  • On the frontal part, the external layer stretches up to the pretracheal fascia. The gland is covered with infrahyoid muscles. Then the lateral part is covered with stern mastoid muscle.
  • On the posterior part, the thyroid gland is attached to the following: cricoid, tracheal cartilage, and cricopharyngeus. The fascia thickening keeps the parts attached. This part is called the Berry’s ligament

Between the two layers and on the frontal part of the lobes, there are two parathyroid glands.

A parathyroid gland, located at the back of the thyroid gland. These are the small endocrine glands which produce parathyroid hormones.

Functions of the thyroid gland

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Did you know that about 25% of the body’s iodide ions are located in the thyroid gland? Being the largest endocrine gland, the thyroid has a lot of functions. Below are the following:

  • It controls the body’s energy usage
  • It produces proteins
  • Manages the body’s hormonal sensitivity by producing its own hormones. The thyroid hormones are triiodothyronine (T3) and tetra iodothyronine (T4), commonly called as thyroxine. T3 and T4 are produced from iodine and tyrosine. These hormones serve as the growth regulator; it also rates the entire body’s functions
  • The Parafollicular cells also called as C cells produce calcitonin. Calcitonin is a 32-amino acid linear polypeptide hormone which reduces blood calcium. This plays a big role in the calcium homeostasis
  • The spherical follicles absorbs iodine from the blood to produce thyroid hormones
  • It serves as the body’s iodine storage

The thyroid gland is connected to the isthmus. The isthmus consists of two attached cone-like shape lobes namely:

  • Right lobe (lobus dexter)
  • Left lobe (lobus sinister)

Each corresponding lobe is approximately 5 cm long, 3 cm wide and 2 cm thick.

The extra lobe

Rarely, about 28-55% of the population has a third lobe in their thyroid gland. This is called the pyramidal lobe (processus pyramidalis), which is often termed as the Lalouette’s pyramid.

The pyramidal lobe is a cone-like shape lobe which stretches from the upper part of the isthmus, through the thyroid cartilage and up to the hyoid bone.

This third lobe serves as the traces of the thyroglossal duct (fetal thyroid stalk).

Health of the thyroid gland

There are various ways to show whether a patient’s thyroid gland is healthy or not.

When a thyroid gland is healthy, it is not visible but it can be palpated as a soft mass. The gland and the entire larynx move whenever a person swallows due to the fascia encasement.

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Image source : Wikipedia by CFCF shared under CC BY-SA 3.0

Below are the following ways to detect the health of the thyroid gland:

Thyroid gland examination

  1. First, the thyroid gland examination is performed by finding the thyroid cartilage
  2. Massage the throat up and down to check if there are any abnormal lumps in the neck.
  3. Then place one hand on each trachea
  4. Move the thyroid tissue smoothly on both sides of the neck. While the other free hand examines the displaced gland tissue
  5. Next, compare the size and texture of both the two lobes via visual inspection. Either manual or bimanual palpation will do.
  6. Lastly, ask to swallow to check the thyroid gland’s movement. Let the patient drink some water to make the examination check easier.

Tip: When palpation is performed during examination, let the patient flex its neck.

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Image source : Wikipedia by CFCF shared under CC BY-SA 3.0

Thyroid diseases

There are various thyroid disorders where the signs and symptoms are painful and uncomfortable. However, there is no need to worry because thyroid problems can be treated immediately.

Most common types of thyroid diseases

Almost all thyroid disorders occur in the abnormalities of the thyroid hormones. Below are the following common types of thyroid disorders:

Goiter

Most thyroid disorders start with a goiter. Did you know that about 90.54% of goiter cases are caused by iodine deficiency?

Goiter is the enlargement of the thyroid gland (thyromegaly). This thyroid disorder is accompanied with swollen neck and larynx.

Thyroid cancer

This type of disorder is indicated by a painless lump in the neck.

Detailed informations about Thyroid Cancer

Non-cancerous thyroid nodules

Many cases include the presence of nodules in the thyroid gland. Fortunately, majority of which are non-cancerous.

In some rare cases many nodules occur. This is called multi-nodular goiter, if the nodule is harmless no treatment is required. However, if the nodule appears to be suspicious by the doctor… this requires surgery.

In addition to that is the toxic adenoma. It is when the nodules begin to develop and discharge thyroid hormones. This may lead to goiter. This interrupts the body’s chemical equilibrium.

Thyroiditis

Thyroiditis is the inflammation of the thyroid gland. In addition to that, there are various disorders which are caused by thyroid inflammation such as:

  • Subacute lymphocytic thyroiditis, it is also called as silent and/or painless thyroiditis.  It is the inflammation of the thyroid gland. This leads to the gland’s hormone leakage which may cause temporary hyperthyroidism.  This type of thyroiditis commonly occurs in females.  Temporary hyperthyroidism usually lasts for weeks. But in some cases, this disorder continues for months.
  • Did you know that only about 0.1-0.7% of the population experience this type of thyroiditis called acute infectious thyroiditis? Acute infectious thyroiditis is caused by bacterial infections such as fungal or parasitic. This is often termed as supportive thyroiditis.
  • Riedel’s thyroiditis is often termed as Riedel’s Struma. It is the chronic version of thyroiditis. In some cases, this strikes as a multi-organ disease (IgG4-related disease). IgG4-related disease attacks the liver, pancreas, kidney, salivary glands, orbital tissues, and retro peritoneum.
  • Postpartum thyroiditis is the inflammation of the thyroid gland after a woman gives birth. This thyroid disorder is usually common among women.

Hypothyroidism

Did you know that about 10% of people with the age of 60 years old and above are affected with hypothyroidism? Hypothyroidism involves the lack of thyroid hormones T3 and T4 production. This is accompanied by the body’s lack of energy. This is due to the production of energy needs an ample amount of thyroid hormones.

Below are the various causes of Hypothyroidism:

  • Iodine deficiency
  • Pituitary disorder
  • Malfunction of the thyroid gland
  • Congenital hypothyroidism. It is a birth deficiency of the thyroid gland
  • When the thyroid gland is surgically removed
  • Excessive exposure from iodide
  • A drug called Lithium
  • Hashimoto’s thyroidism. It is an autoimmune disease where the body destroys the thyroid tissues. When the tissues die, the production of hormone ends

Also, take note when hypothyroidism is not treated for a long period of time. This may lead to myxedema coma. Myxedema coma is a rare but severe condition which requires immediate hormonal treatment.

Hyperthyroidism

  • Hyperthyroidism is often termed as overactive thyroid. This disorder involves too much thyroid hormone production. Moreover, this thyroid disorder can occur in various causes such as:
  • Grave’s disease, is the leading cause of hyperthyroidism. This involves the abnormal anti-body stimulation of the thyroid gland. Thus, it discharges excessive amounts of hormones.
  • Malfunction of the pituitary gland
  • Growth of cancer cells in the thyroid gland

Congenital anomalies

A cyst (persistent thyroglossal duct) is the most common congenital anomaly of the thyroid gland. It is located in the middle part of the neck, in the frontal part of the trachea. This type of thyroid disorder happens to everyone. In some cases, the cyst goes unnoticed until a particular person reaches adulthood.

In addition to that is the thyroid dysgenesis, which involves the appearance of one or more accessory thyroid glands. However, in some cases this can be an asymptomatic thyroid disorder.

Treatments for thyroid problems

Treatments for thyroid problems often occur with the replacement of missing hormones in the body. A lump in the neck is very irritating and uncomfortable, but there is a solution for that. Below are the following treatments for thyroid gland disorders:

Beta blockers

Beta blockers are used to treat the symptoms of hyperthyroidism. The symptoms are as follows:

  • Increased heart rate
  • Heart palpitations
  • Tremors
  • Anxiety

Anti-thyroid drugs

Anti-thyroid drugs are used to control the production of unnecessary thyroid hormones. This is usually prescribed to patients with Grave’s disease. Doctors also recommend taking the pill every 8 hours interval. Also, make a regular visit a health care professional. This is required to undergo frequent blood tests and to track the thyroid disorder’s status.

However, these medications take an ample amount of time to have some noticeable effects on the patient. In addition to that, these have severe side effects such as:

  • Skin rashes
  • Sudden drop of the white blood cells. This affects the body to ward off various infections.

Radioactive iodine-131

Radioactive iodine-131 treatment is a medication which destroys either a portion or the entire thyroid gland. Furthermore, this also destroys the cells inside the thyroid.

Hormone replacement treatment

Hormone replacement theory is used to treat Hypothyroidism. This treatment is usually prescribed by a physician and it usually takes a few weeks for it to take effect. Levothyroxine is the commonly used HRT where a patient is required to take for a lifetime.