The endocrine system is a specialized group of hormone-producing glands and organs. Their function is to regulate the various metabolic processes in the human body, including growth, body temperature, and reproduction, among others. The endocrine system helps keep homeostasis (chemical balance) in the body. An imbalance in hormone activity can result in varied endocrine system disorders. The following is an oveview of the endocrine system.
The endocrine system consists primarily of glands and organs located in various parts of the body. Each of the glands and organs secretes specialized hormones which perform a specific function such as muscle growth, body temperature, water retention, digestion, body energy, reproduction, maturation, glucose levels, etc. The principal glands composing the endocrine system include the hypothalamus, pituitary, pineal, thyroid, parathyroid, adrenal, and gonad glands. The pancreas secretes both digestive enzymes and hormones.
The hypothalamus is situated in the central lower section of the brain. This part of the brain is essential in the control of metabolism, and body temperature; moreover, it secretes hormones that stimulate or suppress the release of hormones in the pituitary gland which in turn signal the secretion of stimulating hormones that control a variety of functions in other endocrine glands.
The pituitary gland is located at the base of the brain below the hypothalamus. It manufactures many hormones that regulate many functions of other endocrine glands. The pituitary gland includes two distinct regions: the anterior lobe (adenohypophysis) and the posterior lobe (neurohypophysis). The release of hormones by the anterior lobe is regulated by the hypothalamus. Hormone secretion in the posterior lobe is controlled by nerve stimulation.
The pineal gland is a small cone-shaped structure located in the middle part of the brain. Specialized secretory cells known as pinealocytes synthesis the hormone melatonin and secrete it into the cerebrospinal fluid which transports it into the blood stream. Melatonin is thought to regulate the body wake-sleep cycle and reproductive development.
The thyroid gland, which is located in the lower front part of the neck, consists of two lobes, one on each side of the trachea. This gland produces thyroid hormones which regulate bone growth, metabolism, blood pressure, heart rate, muscle tone, reproductive functions, and the development of the nervous system and the brain in children. These hormones contain iodine. The release of thyroid hormones is controlled by the pituitary gland.
The parathyroid glands are two pairs of small glands embedded in the connective tissue of the thyroid gland. They release parathyroid hormone or parathormone. This hormone is secreted when calcium levels in the blood are abnormally low. The primary function of the parathyroid hormone is to increase calcium levels to a normal state.
The pancreas (Islets of Langerhans) is an elongated gland located behind the stomach. The pancreas possesses an exocrine region that secretes enzymes and an endocrine portion that secretes insulin and glucagon hormones. Alpha cells secrete glucagon in response to a low concentration of glucose in the blood. Beta cells secrete insulin in response to a high concentration of glucose in the blood.
The adrenal glands are located on the upper portion of each kidney. This pair of glands consists of two parts: the adrenal cortex and the adrenal medulla. The adrenal cortex produces corticosteroids which are hormones that help regulate the body´s metabolism, the immune system, and sexual function. The adrenal medulla produces hormones known as catecholamines, for instance, adrenalin. These hormones help the body deal with emotional stress (flight or fight) by increasing blood pressure and heart rate.
Reproductive glands (gonads):
The reproductive organs are the principal source of reproductive hormones (testosterone). In males, these hormones, known as androgens, are secreted in the testes. These hormones determine many male characteristics, including facial and pubic hair, sexual development and production of sperm. In females, estrogen, progesterone, and eggs are produced in the ovaries. These hormones determine female characteristics, such as menstruation and development of breasts and reproductive organs.