Difference Between Thyroid and Thymus (With Table)

The human body is like a machine, which is made up of several parts. These parts are systems, which are in turn made up of organs. Our body consists of various systems like the nervous system, the lymphatic system, the endocrine system, the digestive system, and many more. The thyroid and thymus also belong to such systems. 

Thyroid vs Thymus

The difference between the thyroid and thymus is that, while the thyroid is an endocrine gland, the thymus is a lymphatic organ. The thyroid belongs to the endocrine system, while the thymus belongs to the lymphatic system. The thyroid produces three different hormones that help with growth and development, while the thymus produces White Blood Cells (WBCs) that help the body fight infections and diseases.

The thyroid is an endocrine gland, i.e., the hormones secreted by it are poured directly into the bloodstream. It is a butterfly-shaped organ situated on the windpipe. It has two lobes, and they are joined by the isthmus. The gland is also sheathed by a thin fibrous capsule. There can be a few variations on the size and shape of the gland.

The thymus, on the other hand, is a part of the lymphatic system. It produces WBCs called the T cells and a hormone called thymosin. These cells then enter the bloodstream via the thymus. It is a small, asymmetrical, and flat-shaped organ situated in front of the heart. It is also sheathed by a capsule.

Comparison Table Between Thyroid and Thymus

Parameters of ComparisonThyroidThymus
SystemThe thyroid is an endocrine gland.The thymus is a lymphatic organ.
SecretionsThe thyroid produces three different hormones: thyroxine, Triiodothyronine, and calcitonin.The thymus produces Thymosin and T Cells.
ShapeThe thyroid is a butterfly-shaped gland having two lobes.The thymus is an asymmetrical, flat-shaped organ.
LocationThe thyroid is located on the windpipe, just below Adam’s Apple.The thymus is located in the central part of the chest, in front of the heart.
Main FunctionsThe thyroid performs three main functions: Metabolic, Cardiovascular, and Developmental.The thymus performs three main functions: T Cell maturation, Positive Selection, and Negative selection.
DiseasesHypothyroidism, hyperthyroidism, goiter, and thyroid cancer are some of the common diseases related to thyroid.Immunodeficiency, autoimmune, thymoma, myasthenia gravis, and thymic cyst are some common diseases related to the thymus.

What is Thyroid?

The thyroid gland is butterfly-shaped that wraps around the windpipe. The gland has two lobes, which lie on either side of the windpipe. These lobes are joined by an isthmus. The thyroid is an endocrine gland and produces three different types of hormones. These three hormones are Thyroxine, Triiodothyronine, and Calcitonin.

Thyroxine (T4) and Triiodothyronine (T3) are hormones that regulate the metabolic rate of our body. Thyroxine which is T4, is converted to T3 in the cells and tissues of our body. Both these hormones are made in the follicular cells of the gland. The production of both these hormones is regulated by Thyroid Stimulating Hormone (TSH), which is produced by the anterior pituitary gland.

The thyroid gland also produces a peptide called calcitonin. This hormone is secreted by the parafollicular cells, also known as the C-Cells. Its function is to help in regulating the calcium and phosphate levels in our body.

There are various diseases related to the thyroid.

Hypothyroidism: It is a condition in which there is a deficiency in the production of thyroid hormones. This disease slows down metabolism. The various symptoms of this disease are tiredness, coldness, weight gain, poor concentration, and depression.

Hyperthyroidism: This is a condition where the gland secretes an excess of the thyroid hormones. This disease increases the metabolic rate, causes weight loss, heat intolerance, sore and gritty eyes.

Thyroid cancer is also a common disease, and so is postpartum thyroiditis, which is caused after the birth of a child. While this is a curable disease, it reoccurs every time a woman gives birth. Another common disease related to the thyroid is Goiter which is usually caused due to a lack of iodine.

The process of removing the thyroid is called thyroidectomy.

What is Thymus?

The thymus is a small, asymmetrical, flat-shaped organ situated at the ventral ( front) side of the chest, behind the sternum, just in front of the heart. The organ has two lobes and is surrounded by a capsule. It is a lymphoid organ and belongs to the immune system. The thymus produces thymosin and T Cells. Thymosin is a protein that stimulates the production of the T Cells, which are WBCs. The main purpose of a WBC is to fight disease-causing microbes.

T Cells produced in the thymus are immature. These immature T Cells are called thymocytes. There are also epithelial cells present in the thymus, which help with the maturation of the T Cells. The thymus is the most active during the neonatal and pre-adolescent stages. With time, the organ shrinks and is replaced by fatty tissue.

The most common diseases are related to the thymus are:

Myasthenia Gravis (MG): It is a chronic autoimmune disease that leads to weakness in muscles.

Thymic cancers are of two types:

Thymomas, where the tumor originates from the epithelial cells of the organ, and Lymphomas, where the T Cells form a subset of acute lymphoblastic leukemia.

The process of removing the thymus is known as thymectomy.  

Main Differences Between Thyroid and Thymus  

  1. The thyroid is a gland, whereas the thymus is an organ.
  2. The thyroid belongs to the endocrine system, whereas the thymus belongs to the lymphatic system.
  3. The thyroid produces hormones that help with growth, metabolism, and cardiovascular functions, whereas the main functions of the thymus are T Cell maturation, Positive and Negative selection.
  4. The thyroid is located on the windpipe, whereas the thymus is present in front of the heart.
  5. The thymus gets replaced as one age, whereas the thyroid never degenerates.
  6. The thyroid is active throughout one’s life, whereas the thymus is most active during the neonatal and pre-adolescent periods of one’s life.
  7. The secretion of thyroid hormones is controlled by the anterior pituitary gland, whereas the thymus is regulated by cytokines.  


In conclusion, we can say that the thyroid and the thymus perform very different functions in our bodies when compared to each other. The thymus is associated with the immune system of our body, while the thyroid deals with the development and growth of our body. The thyroid is a gland producing hormones, while the thymus produces White Blood Cells. Thymus also degenerates over years while the thyroid is active throughout human life. However, while the thymus does degenerate, the body does continue to produce T Cells (WBCs). The thyroid is also much more prone to diseases and malfunctions than the thymus is.


  1. https://www.sciencedirect.com/science/article/pii/S0140673667921770
  2. https://www.jci.org/articles/view/119032

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