Difference between Thyroid and Parathyroid

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.

Thyroid

Parathyroid

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

It is large in size

It is small in size

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

The thyroid gland is composed of follicular cells and stromal tissues

The parathyroid gland is composed of chief cells and oxyphil cells

Follicular cells synthesise thyroxine (T4) and triiodothyronine (T3)

Chief cells synthesise and release parathormone (PTH)

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

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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