The key difference between thyroid and parathyroid is that thyroid gland is an endocrine gland that produces hormones that regulate the metabolism of the body while parathyroid gland is an endocrine gland that produces hormones that control the calcium ion levels in the blood.
The human endocrine system secretes hormones directly to the circulation. These hormones will act on the specific receptors on specific cells to bring about necessary changes required for development in physical and psychological aspects, reproductive life, day to day well being, etc. The central control of the endocrine system is through neural, hormonal and humoral stimuli acting on the hypothalamus, which in turn activates the pituitary gland, which secretes the controller hormones required for other endocrine glands. The thyroid and parathyroid glands are important components of the whole endocrine system of the human body.
CONTENTS
1. Overview and Key Difference
2. What is Thyroid
3. What is Parathyroid
4. Similarities Between Thyroid and Parathyroid
5. Side by Side Comparison – Thyroid vs Parathyroid in Tabular Form
6. Summary
What is Thyroid?
The thyroid gland is an endocrine gland situated at the front of the neck, just below the laryngeal prominence (Adam’s apple). It is a single gland with two lobes and a central, connecting isthmus arranged like a butterfly. Moreover, it has two blood supplying vessels. They are the superior and inferior thyroid vessels. The hormonal control of this gland is through a cascade where the hypothalamus secretes thyrotrophin releasing hormone (TRH), which in turn causes the release of thyroid stimulating hormone (TSH), which acts on the thyroid gland to bind iodine to form thyroid hormones T3 and T4. These hormones are important for cellular growth, brain growth and intelligence and the overall well being of the person. A deficit causes hypothyroidism, and an excess causes hyperthyroidism.
Figure 01: Thyroid Gland
Thyroid gland is also a target for tumours. They range from benign to highly malignant, affecting many decades of life.
What is Parathyroid?
Parathyroid glands are usually 4 separate glands, positioned on the posterior surface of the thyroid gland with two each on either lobe. But, there may be varying amounts of these glands. Inferior thyroid artery mainly supplies blood to these glands. The release of hormones from this gland is not regulated by the hypothalamic-pituitary axis, but by the calcium-sensing receptors in the gland. The parathyroid hormone (PTH) regulates the serum calcium levels through acting in the gut, kidneys, bone and Vitamin D. However, the calcitonin hormone antagonizes the action of PTH.
Figure 02: Parathyroid Gland
Excess of PTH causes hyperparathyroidism, and a deficit causes hypoparathyroidism. There may be a very rare occurrence of malignancies at this gland too.
What are the Similarities Between Thyroid and Parathyroid?
- Thyroid and parathyroid are two endocrine glands.
- They release hormones.
- Moreover, the location of both are the front of the neck, just below the laryngeal prominence.
- Also, both glands are important in order to maintain the homeostasis of the body.
What is the Difference Between Thyroid and Parathyroid?
Thyroid is an endocrine gland, which is butterfly shaped, while parathyroid is a small endocrine gland, which is the size of a rice grain. Importantly, thyroid gland secretes hormones to regulate growth and development by regulating the rate of metabolism while parathyroid gland secretes hormones that regulate the calcium level in the body. So, this the key difference between thyroid and parathyroid. Moreover, thyroid gland is a single gland, whereas parathyroids are four or more separate glands. Thus, this is a structural difference between thyroid and parathyroid.
Furthermore, the thyroid gland has two or more major blood supplies, whereas the parathyroid has a single major blood supply. Also, a significant difference between thyroid and parathyroid is that the thyroid gland is controlled by the hypothalamic-pituitary axis while the parathyroid is controlled by Ca2+ sensors on the gland. Besides, the thyroid hormones affect almost all the cells in the body, whereas parathyroid hormones are limited to a discrete few tissues. Additionally, a further difference between thyroid and parathyroid is that the occurrence of malignancies is very common in the thyroid gland, whereas it is very rare in the parathyroid glands.
Summary – Thyroid vs Parathyroid
In summary, thyroid and parathyroid are two endocrine glands having important functions in the human body. Both are present in the anterior neck and are closely associated with each other. These glands are very important due to the actions of the hormones they secrete. There is only one thyroid gland while there are four parathyroid glands. Moreover, thyroid gland is a large gland and has the shape of a butterfly while parathyroid gland is a small gland which is the size of a rice grain. Hormones of the thyroid gland regulate the metabolism while parathyroid hormones regulate the calcium level in the body. Thus, this is the summary of the difference between thyroid and parathyroid glands.
Reference:
1. “Thyroid and Parathyroid Glands – Anatomy Pictures and Information.” Innerbody, Available here.
2. “Thyroid.” Wikipedia, Wikimedia Foundation, 18 Apr. 2019, Available here.
Image Courtesy:
1. “1811 The Thyroid Gland” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013 (CC BY 3.0) via Commons Wikimedia
2. “1814 The Parathyroid Glands” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013 (CC BY 3.0) via Commons Wikimedia