Difference Between Thyroid and Thymus

The thyroid and thymus are both endocrine glands that are located in the neck region and play an important role in the endocrine system. However, despite their similar location, the thyroid and thymus have several distinct differences.

What is Thyroid?

The thyroid functions as an endocrine system organ. Two different hormones produced by this gland control metabolic rate.

Structure − Thyroid anatomy consists of four lobes located in the base of the human neck. In the lobes, follicles are found, which are encased in epithelia. Follicles are where hormones are synthesised.

Function − The thyroid's two hormones help regulate metabolic rate. Production of hormones includes thyroxine (T4) and triiodothyronine (T3). Each of the thyroid's follicles is responsible for producing them from iodine molecules.

Regulation − Hypothalamus and anterior pituitary gland hormones regulate thyroid hormone release. Each of these brain areas is part of a negative feedback loop that regulates their respective activities. The hypothalamus becomes active when there are insufficient levels of thyroid hormone in the blood. Thyrotropin-releasing hormone is secreted as a result, prompting the anterior pituitary to release thyroid-stimulating hormone, which, in turn, encourages the thyroid to produce and release the two thyroid hormones into the circulation.

Disorders − Problems with the thyroid gland often fall into two categories: either the gland is producing too little or too much of the hormones that regulate metabolism. Due to an underactive thyroid, a lack of hormone production can cause a sluggish metabolism, leading to weight gain, as well as dry, brittle hair. In contrast, a person with an overactive thyroid frequently has high heart rate and weight loss.

What is Thymus?

Triangular in form, the thymus is a lymphatic system organ that plays a role in immunological response.

Structure −The thymus is largest when a person is a foetus or a newborn, shrinks gradually as they mature, and is significantly shrunken by the time they reach advanced age. The thymus consists of two components, or lobules, the outer capsule and the inner medulla. Reticulocytes and lymphocytes are both found in the thymus.

Function − The thymus's job is to prevent infections, especially in the growing foetus and newborn kid, by producing antibodies to fight off harmful pathogens. Bone marrow produces white blood cells, which then go through a final stage of development to become T-cells. Several subsets of T cells contribute to cell-mediated immunity in distinct ways.

Regulation − A mechanism including the hypothalamus of the brain and the pituitary gland regulates the thymus' generation of immune system cells and the thymus' maturation of cells. The brain may tell the pituitary to signal the thymus to make more T cells when a cell-mediated immune response is needed.

Disorders − Hypogammaglobulinemia and myasthenia gravis are two thymus-related disorders. The autoimmune disease myasthenia gravis is caused by an overactive thymus that makes molecules called antibodies that target the receptors on muscle cells.

Differences: Thyroid and Thymus

The following table highlights the major differences between Thyroid and Thymus −





The thyroid is an endocrine gland that produces hormones to regulate the metabolic rate in the body.

The thymus is an organ of the lymphatic system where white blood cells develop further into T cells.


The thyroid gland consists of two lobes, each comprised of follicles surrounded by epithelia.

The thymus consists of an outer capsule and inner medulla section and is made up of two lobules.

Changes in size with age

The thyroid does not change in size as you age unless there is a problem.

The thymus does change in size and actually becomes smaller as you age.

What it produces

The hormones thyroxine and triiodothyronine are secreted by the thyroid gland.

Mature lymphocytes called T cells are formed by and produced by the thymus from other white blood cells.


The function of the thyroid gland is to regulate metabolism and metabolic rate.

The function of the thymus is to produce T cells for the cell-mediated immune response.


Thyroid problems include overproduction and underproduction of thyroid hormones.

Thymus problems include myasthenia gravis and hypogammaglobulinemia.


The thyroid and thymus are two distinct endocrine glands that have different functions, hormones, and diseases. The thyroid regulates the body’s metabolic rate, while the thymus helps protect the body from infections and diseases.

Understanding the differences between these two glands is important for maintaining good health and preventing diseases.

Updated on: 07-Apr-2023


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