Difference Between Thyroid and Parathyroid

The thyroid and parathyroid glands are both endocrine glands located in the neck region of the body. While both glands are involved in hormone secretion and play vital roles in the regulation of body functions, they differ in terms of their structure, function, and hormone production.

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 Parathyroid?

The parathyroids are small endocrine glands that are located on the back of the thyroid gland in the neck region, and they produce parathyroid hormone.

Structure of Parathyroid − They are small round glands that consist of oxyphil cells and chief cells and are set apart from the thyroid by means of a connective tissue layer. It is the chief cells that produce parathyroid hormone (PTH) that is released into the bloodstream.

Function of Parathyroid − The parathyroid glands function is to produce PTH which works to regulate the calcium levels in the body, which is important since our nervous system relies on calcium ions to function. The PTH triggers the release of calcium ions from bone tissue by activating osteoclast cells which break down bone. It also stops the activity of the osteoblasts which are the bone cells that are involved in actually laying down more bone. It also activates the production of calcitriol which is a hormone that helps trigger the intestines to absorb more calcium from food.

Parathyroid Regulation: The secretion of parathyroid hormone is largely controlled by the levels of calcium that are in the bloodstream. The alterations in bloodstream concentrations of calcium are sensed by G-protein coupled receptors of the chief cells in the parathyroid gland. A negative feedback mechanism is in play here with low calcium triggering more PTH to be released. As calcium levels in the blood plasma increase so the PTH is triggered to stop releasing the hormone.

Disorders involved in Parathyroid − There can be both too much activity of the parathyroid glands, or too little. An overactive gland causes hyperparathyroidism. This disorder can cause excessive amounts of calcium to be taken out of the bones. The problem then is that bone density may weaken to such an extent that people are likely to have bone fractures. It also has a negative effect on the nervous system. Too little activity of the gland causes hypoparathyroidism, which can occur due to surgery or from an injury. This has an adverse effect on the nervous system and can lead to convulsions and muscle spasms and twitching.

Differences: Thyroid and Parathyroid

The structure of the thyroid and parathyroid glands also differs significantly. The thyroid gland is made up of two lobes connected by a central isthmus, and it is surrounded by a capsule. The gland is composed of numerous follicles, which are clusters of cells that produce and store thyroid hormones. The parathyroid gland, on the other hand, is much smaller and is located on the back of the thyroid gland. Each parathyroid gland consists of two types of cells: chief cells, which produce PTH, and oxyphil cells, whose function is still unclear.

The hormones produced by the thyroid and parathyroid glands also differ in their actions and effects on the body. Thyroid hormones regulate metabolism, body temperature, heart rate, and the function of other organs. Too much thyroid hormone can lead to hyperthyroidism, a condition characterized by weight loss, tremors, increased heart rate, and anxiety. Too little thyroid hormone can lead to hypothyroidism, a condition characterized by weight gain, fatigue, cold intolerance, and depression.

PTH, on the other hand, regulates calcium and phosphorus levels in the blood. Too much PTH can lead to hyperparathyroidism, a condition characterized by high levels of calcium in the blood, which can lead to kidney stones, osteoporosis, and other complications. Too little PTH can lead to hypoparathyroidism, a condition characterized by low levels of calcium in the blood, which can lead to muscle cramps, spasms, and seizures.

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





The thyroid is a gland of the endocrine system found in the neck region, which secretes thyroid hormone.

The parathyroids are glands found attached to the thyroid that secretes parathyroid hormone.


The anatomy of the thyroid includes epithelial cells and a colloid in the follicle region.

The anatomy of the parathyroids includes oxyphil and chief cells.


The thyroid is a butterfly-shaped two lobe structure.

The parathyroid has no lobes.

Size and number

There is only one thyroid gland which is quite large in size.

There are four or more parathyroid glands which are small structures.


The hormones produced by the thyroid include triiodothyronine (T3) and thyroxine (T4).

The hormone produced by the parathyroid is parathyroid hormone (PTH).


The secretion of hormones from the thyroid gland is regulated by TRH from the hypothalamus and TSH from the anterior pituitary, responding to hormone levels.

Secretion of parathyroid from the parathyroid gland is regulated by G- coupled receptors on the chief cells responding to calcium levels.


In summary, the thyroid and parathyroid glands are both endocrine glands located in the neck region of the body. While the thyroid gland produces hormones that regulate metabolism, growth, and development, the parathyroid gland produces hormones that regulate calcium and phosphorus levels in the blood.

These glands differ in terms of their structure, function, and hormone production, and an imbalance in their hormones can lead to a range of health complications. Understanding the difference between these two glands is essential for maintaining good health and preventing illness.

Updated on: 07-Apr-2023


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