Endocrine System and the Role of Endocrine Glands

The endocrine glands of human beings are well studied than those of any other animals because of their role in the maintenance of human health.

The organized endocrine tissues or organs in the human body includes

  1. Pituitary Gland
  2. Pineal Gland
  3. Thyroid Gland
  4. Parathyroid Gland
  5. Adrenal Gland
  6. Pancreas
  7. Thymus Gland
  8. Gonads


Pituitary Gland

Pituitary Gland

The pituitary also called hypophysis is a small unpaired round body. It is located immediately beneath the hypothalamus and is attached to the infundibulum.

It is divided into anterior pituitary and posterior pituitary which are also called as adenohypophysis and neurohypophysis respectively.

Anterior and Posterior Pituitary

Functions of Anterior Pituitary

The main role of the anterior pituitary is the secretion of six important protein hormones. They include

  • Growth Hormone
  • Prolactin
  • Thyroid Stimulating Hormone (TSH)
  • Adrenocorticotrophic Hormone (ACTH)
  • Follicle Stimulating Hormone (FSH)
  • Leutinizing Hormone (LH)

Functions of Posterior Pituitary

It stores and releases two hormones called Oxytocin and Vasopressin which are actually synthesized by Hypothalamus and are called Neuro-secretions.

Oxytocin works on smooth muscles of the body and induces their contractions. In females, it stimulates powerful contractions of the uterus during childbirth and ejection of milk from mammary glands.

Vasopressin affects the kidney and stimulates reabsorption of water and electrolytes by the distal convoluted tubule.


Pineal Gland

Pineal Gland

It is also known as “Epiphysis Cerebri“. It is located on the dorsal surface of the diencephalon. It secretes a hormone called Melatonin.

It plays a very important role in the regulation of Circadian Rhythms (24 hrs) of our body. It also helps in maintaining the normal rhythm of the sleep-wake cycle and body temperature.

Thyroid Gland

Thyroid Gland

It is the largest endocrine gland and is endodermal in origin. It lies close to the body surface, in the neck near the junction of the larynx and the trachea.

It releases 2 hormones namely Thyroxin and Calcitonin.

The thyroid gland consists of follicular cells that release Tetra-iodothyronine or Thyroxine (T4) and Tri-iodothyronine (T3). It plays an important role in the regulation of basal metabolic rate.

Parafollicular cells of thyroid produce a polypeptide hormone called Thyrocalcitonin. It plays an important role in maintaining proper levels of calcium and phosphates in the blood.


Parathyroid gland

Parathyroid Glands

In humans, there are 4 parathyroid glands located on the backside of the thyroid gland. Each lobe of the thyroid gland has a pair of parathyroid glands.

It secretes a hormone called Parathormone. The secretion of this hormone helps in maintaining the calcium levels in the circulatory fluids.

It promotes the conversion of Vitamin D into its active form, the hormone called Calcitriol.

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