Thyroid

You have a small part in your neck.

It looks like a butterfly. It has two sides joined in the middle.

This part helps your body grow. It also helps you use food for energy. This happens because it sends out special signals. These signals tell your body how fast to work.

This tiny part is very helpful!

You have a small part in your neck called the thyroid.

It is shaped like a butterfly or the letter H. It has two sides called lobes. A thin band of tissue joins them. This band is called the isthmus.

Inside the thyroid are tiny round parts called follicles. These follicles make special signals called hormones. The thyroid makes three main hormones. Two are called T3 and T4. They help your body grow and use food for power. The third is called calcitonin. This helps manage calcium in your body.

Your brain helps control the thyroid. A part called the pituitary gland sends a signal called TSH. This signal tells the thyroid to work. Other parts of the brain help too. If the thyroid makes too many hormones, it is called hyperthyroidism. If it makes too few, it is called hypothyroidism. Not having enough iodine can cause this. Iodine is very important for healthy growth.

The thyroid is a very important gland in your body.

It is shaped like a butterfly or the letter H. This gland sits in your neck, just below your Adam's apple. It is made of two connected sides called lobes. A thin band of tissue called the isthmus joins these lobes together.

The thyroid helps manage how your body uses energy. It also helps children grow and develop properly. Without it, your body would struggle to stay healthy.

Inside the gland, tiny round units called follicles do the work.

These follicles are filled with a substance called colloid. The thyroid makes three main hormones to send signals. Two of these are called T3 and T4. They are made using iodine and a protein called thyroglobulin. The third hormone is called calcitonin, which helps manage calcium.

These hormones travel through your blood to tell your body what to do.

Your brain acts like a manager for the thyroid. First, a part of the brain called the hypothalamus sends a signal. This signal tells the pituitary gland to release thyroid-stimulating hormone, or TSH.

When TSH reaches the thyroid, it tells the follicles to make T3 and T4. This creates a feedback loop to keep everything balanced. If hormone levels get too high or too low, the brain sends different signals. This system ensures your body gets exactly what it needs.

Scientists have studied the thyroid for a long time. In 1664, Geoffery Websterson discovered the tiny cells that make up the gland. The thyroid can sometimes look different in every person. Some people have an extra part called a pyramidal lobe.

This extra lobe is found in about 18% to 44% of people. In adults, the whole gland usually weighs about 25 grams. It is often slightly larger in women than in men.

Sometimes the thyroid does not work quite right. Hyperthyroidism happens when the gland makes too many hormones. Hypothyroidism happens when the gland makes too few.

A common cause of low hormones is not having enough iodine. Iodine is a mineral that the thyroid must have to work. In some places, a lack of iodine is a big health problem for children. Keeping the thyroid healthy helps the whole body stay strong.

The thyroid is a vital endocrine gland found in vertebrates. In humans, it is a butterfly-shaped organ located in the neck. It sits just below the Adam's apple, surrounding the cricoid and tracheal cartilages.

The gland consists of two connected lobes, a left and a right. A thin band of tissue called the isthmus connects these two lobes. In adults, the entire gland typically weighs about 25 grams. Each individual lobe is roughly 5 cm long, 3 cm wide, and 2 cm thick. The isthmus is smaller, measuring about 1.25 cm in both height and width.

At a microscopic level, the thyroid is composed of specific functional units. The primary unit is the thyroid follicle, which is a tiny spherical grouping of cells. These follicles are between 0.02 and 0.9 mm in diameter.

Each follicle is lined with a single layer of follicular cells, also known as thyrocytes. Inside the follicle is a fluid-filled space called the lumen. This lumen contains a substance called colloid. The colloid is a concentrated solution of thyroglobulin, which is a protein used to make hormones. Scattered among these follicles are parafollicular cells, or C cells, which serve a different purpose.

The thyroid produces three essential hormones to regulate body functions. The first two are thyroid hormones: triiodothyronine (T3) and thyroxine (T4). These are created by combining iodine with the amino acid tyrosine. T3 contains three iodine atoms, while T4 contains four.

These hormones are critical for the basal metabolic rate. They influence how the body breaks down fats and uses glucose. They also affect heart rate, breathing, and how much oxygen the body consumes. The third hormone is calcitonin, a peptide hormone secreted by the parafollicular cells. Calcitonin plays a specific role in maintaining calcium homeostasis, or the balance of calcium in the body.

Control of these hormones works through a complex chemical communication system. The process begins in the brain with the hypothalamus. The hypothalamus produces thyrotropin-releasing hormone (TRH). This hormone signals the anterior pituitary gland to release thyroid-stimulating hormone (TSH).

When TSH reaches the thyroid, it stimulates the follicular cells to produce T3 and T4. This system uses a negative feedback loop to maintain balance. If hormone levels become too high, the brain reduces the release of TRH and TSH. This ensures the body maintains the precise levels of hormones needed for health.

The development of the thyroid begins very early in an embryo. At about three to four weeks of gestation, the thyroid appears as a growth in the floor of the pharynx. It then descends toward the neck through a narrow canal called the thyroglossal duct.

By the end of the fifth week, this duct usually disappears. The thyroid eventually reaches its final position in front of the trachea. By 11 weeks, TSH becomes measurable in the fetus. By 18 to 20 weeks, the production of thyroxine (T4) reaches levels that allow the fetus to be self-sufficient. This is vital because the fetus needs these hormones for healthy brain development.

While the thyroid follows a general pattern, there are many anatomical variations. Some people possess a third lobe called a pyramidal lobe, also known as Lalouette's pyramid.

This lobe is a remnant of the thyroglossal duct and is present in 18.3% to 44.6% of people. Another variation is Zuckerkandl's tubercle, which is a small horn at the back of the lobes. The gland is also attached to the neck structures by Berry's ligament. This ligament causes the thyroid to move up and down when a person swallows. These variations show how much individual anatomy can differ.

When the thyroid does not function correctly, it leads to various medical conditions. Hyperthyroidism occurs when the gland secretes excessive amounts of thyroid hormones. A common cause of this is Graves' disease, which is an autoimmune disorder. Conversely, hypothyroidism occurs when there is a deficiency in hormone secretion.

In many regions, the most common cause of hypothyroidism is a lack of iodine. In iodine-sufficient areas, Hashimoto's thyroiditis is a frequent cause. In areas lacking iodine, hypothyroidism is a leading cause of preventable intellectual disability in children. Understanding these connections helps scientists treat metabolic and developmental disorders.