Thyroid and parathyroid are endocrine glands that produce hormones. These hormones regulate various metabolic processes. The main thyroid hormones are thyroxine (T4) and triiodothyronine (T3). They are involved in regulating the basal metabolic rate and metabolism of carbohydrates, proteins and fats. The parathyroid gland produces a parathyroid hormone (PTH) or parathormone. It regulates calcium balance in the body, along with thyrocalcitonin (TCT), which is a thyroid hormone.
Let us now learn more about thyroid and parathyroid glands and their differences.
Thyroid
Thyroid is an endocrine gland. Thyroid gland is present at the neck region and two lobes of the gland are present on both sides of the trachea connected by the isthmus. They secrete various hormones such as tetraiodothyronine or thyroxine (T4), triiodothyronine (T3) and thyrocalcitonin (TCT). The main functions of thyroid hormones are as follows:
- Thyroid hormones influence the basal metabolic rate.
- They regulate the metabolism of carbohydrates, proteins and fats.
- They also regulate water and electrolyte balance in the body.
- Thyroid hormones stimulate the process of RBC production (erythropoiesis).
- Thyrocalcitonin (TCT) is involved in regulating blood calcium levels.
Iodine is essential for thyroid hormone synthesis. Deficiency of dietary iodine leads to hypothyroidism. Thyroid hormone imbalance leads to various diseases such as goitre, cretinism, exophthalmic goitre, Grave’s disease, thyroid cancer, etc.
The synthesis and release of thyroid hormones is regulated by TRH (Thyrotropin-releasing hormone) from the hypothalamus and TSH (Thyroid-stimulating hormone) from the anterior pituitary.
Parathyroid
Two pairs of parathyroid glands are present on the back of the thyroid gland, one pair in each lobe. It secretes a peptide hormone called parathyroid hormone or PTH. The biological function of PTH is to increase the Ca2+ levels in the blood, i.e. it is a hypercalcemic hormone. It increases calcium level by bone demineralisation, reabsorption of Ca2+ by the renal tubules, and by increasing absorption from digested food.
The release of parathyroid hormone is regulated by calcium levels in the blood.
Difference between Thyroid and Parathyroid
The table below shows the main differences between Thyroid and Parathyroid.
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Thyroid is an endocrine gland present at the neck region on both sides of the trachea |
Parathyroid glands are present on the backside of the thyroid gland |
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It is large in size |
It is small in size |
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Only one thyroid gland is present which has two lobes connected by isthmus |
Four parathyroid glands are present, two in each lobe of thyroid gland |
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The thyroid gland is composed of follicular cells and stromal tissues |
The parathyroid gland is composed of chief cells and oxyphil cells |
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Follicular cells synthesise thyroxine (T4) and triiodothyronine (T3) |
Chief cells synthesise and release parathormone (PTH) |
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Secretion of thyroid hormones is regulated by TRH (Thyrotropin-releasing hormone) from the hypothalamus, and TSH (Thyroid-stimulating hormone) from the anterior pituitary |
Secretion of parathyroid hormone is regulated by circulating Calcium levels |
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It regulates the metabolism of carbohydrates, fats and proteins |
It regulates calcium level in the body |
Frequently Asked Questions
What are the 3 functions of the thyroid gland?
The three main functions of the thyroid gland are as follows:The three main functions of the thyroid gland are as follows:
- Regulation of the basal metabolic rate (BMR).
- Regulation of the metabolism of carbohydrates, proteins and fats.
- They stimulate the process of RBC production (erythropoiesis).
What hormones do a parathyroid release?
Parathyroid glands release parathyroid hormone (PTH) or parathormone. It regulates calcium levels in the body.
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