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Endocrine Gland

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A class of signalling molecules known as Hormones are delivered from distant organs in multicellular animals to control physiology and behaviour. Hormones are necessary for the healthy development of animals, plants, and fungi. Numerous different types of molecules can be categorised as hormones due to the broad definition of a hormone (as a signalling molecule that exerts its effects far from its place of creation). 

Among the compounds that can be categorised as hormones are eicosanoids (such as prostaglandins and thromboxanes), steroids (such as oestrogen and brassinosteroid), amino acid derivatives (such as epinephrine and auxin), proteins or peptides (such as insulin and CLE peptides), and gases (e.g. ethylene and nitric oxide).

Hormones are the primary means through which organs and tissues communicate. The physiological and behavioural processes of digestion, metabolism, respiration, sensory perception, sleep, excretion, lactation, stress induction, growth and development, locomotion, reproduction, and mood regulation are all regulated by hormones in vertebrates. Almost every phase of plant development, from germination to senescence, is regulated by hormones

Endocrine System

The body produces hormones, which are chemicals that control the activity of cells or organs, and the endocrine system is made up of glands that generate and secrete hormones. These hormones control the body’s metabolism, or how the physical and chemical processes of the bodywork, as well as sexual function and development. The hormones are released into the bloodstream and may have an impact on a single organ or a number of them.

Chemical messengers known as hormones are produced by the body. For the proper functioning of various bodily components, they transmit information from one set of cells to another.

The hypothalamus, pituitary, thyroid, parathyroid, adrenal, pineal body, and reproductive organs are the primary glands of the endocrine system (ovaries and testes). This system also includes the pancreas, which aids in both digestion and hormone production.

The way a thermostat controls a room’s temperature is similar to how the endocrine system is regulated through feedback. The pituitary gland receives a signal in the form of a “releasing hormone” from the hypothalamus, which prompts the pituitary to emit a “stimulating hormone” into the bloodstream in order to control certain hormones. The target gland is then signalled by the stimulating hormone to release its own hormone. The hypothalamus and the pituitary gland stop the releasing hormone and the stimulating hormone from being secreted as the level of this hormone rises in the blood, which slows the release by the target gland. The hormones that the pituitary gland controls are stabilised in the circulation thanks to this mechanism.

Anatomy of Endocrine System

An intricate system of glands and organs makes up the endocrine system. The human body’s processes like metabolism, energy level, reproduction, growth and development, and response to injury, stress, and mood are all regulated and coordinated by hormones. The endocrine system is made up of the following components:

Endocrine System



The lower central region of the brain contains the hypothalamus. The metabolism, body temperature, and feelings of fullness are all controlled by this area of the brain. Releasing hormones in the hypothalamus indicate the release of stimulating hormones. Somatostatin, another hormone secreted by the brain, forces the pituitary gland to stop producing growth hormone.

Pituitary Gland

Smaller than a pea, the pituitary gland is situated underneath the hypothalamus at the base of the brain. Because it generates hormones that regulate many of the actions of other endocrine glands, it is frequently regarded as the most crucial component of the endocrine system. Hypopituitarism is a condition in which the pituitary gland fails to generate enough of one or more of its hormones.

The anterior lobe and the posterior lobe are the two sections of the pituitary gland. The hypothalamus controls the production of the following hormones by the anterior lobe:

  1. Growth hormone: Stimulates bone and tissue growth (growth failure is caused by a lack of growth hormone). Adults who lack enough growth hormone have trouble maintaining healthy levels of body fat, muscle mass, and bone density. Additionally, it affects emotional health.
  2. Thyroid-stimulating hormone (TSH): Stimulates the production of thyroid hormones by the thyroid gland. Hypothyroidism is the medical term for the absence of thyroid hormones, which can be caused by either a pituitary or thyroid disorder.
  3. Adrenocorticotropin hormone (ACTH): Stimulates the production of a number of related steroid hormones by the adrenal gland.
  4. Luteinizing hormone (LH) and follicle-stimulating hormone (FSH): Estrogen and progesterone in women and testosterone in men are the steroid hormones that regulate sexual activity and production.
  5. Prolactin: Hormone that increases milk production in females.

Thyroid Gland

In the front lower area of the neck, there is a thyroid gland. The thyroid gland makes thyroid hormones, which control the body’s metabolism. Additionally, it affects how bones grow and how children’s brains and neurological systems develop. The release of thyroid hormones is regulated by the pituitary gland. Additionally, thyroid hormones support healthy digestion, muscular tone, blood pressure, heart rate, and reproductive processes.

Parathyroid Glands

The parathyroid glands are two pairs of tiny glands, one pair on each side, implanted in the thyroid gland’s surface. They discharge parathyroid hormone, which affects the blood calcium levels and bone metabolism.

Adrenal Glands

On top of each kidney are two triangular-shaped glands known as the adrenals. There are two components to the adrenal glands. The inner portion is known as the adrenal medulla, and the outside portion is known as the adrenal cortex. The body’s outer layer creates corticosteroid hormones, which control the body’s metabolism, water and salt balance, immune system, and sexual function. Catecholamine hormones are produced by the adrenal medulla, which is located inside (for example, adrenaline). By raising the heart rate and blood pressure, these hormones assist the body in coping with mental and physical stress.

Pineal body

In the centre of the brain, beneath the corpus callosum, is where you’ll find the pineal body. Melatonin, a hormone it generates, aids the body in recognising when it is time to sleep.


Behind the stomach, across the rear of the belly, is where the pancreas is situated. In addition to producing hormones, the pancreas is involved in digestion. The pancreas secretes hormones like glucagon and insulin that control blood sugar levels.


The ovaries of a woman are situated below the opening of the fallopian tubes on both sides of the uterus (tubes that extend from the uterus to the ovaries). The ovaries generate oestrogen and progesterone in addition to housing the egg cells required for reproduction.


The male reproductive system has two oval-shaped structures called testes, sometimes known as testicles. They are housed in a skin sac known as the scrotum. In the front of the pelvic area, close to the upper thighs, the scrotum hangs outside the body.

The synthesis and preservation of sperm until they are ready for ejaculation depend on structures within the testes. A hormone called testosterone is also produced by the testes. This hormone is in charge of sex desire, conception, and the growth of bone and muscle mass.

Hormones of Hypothalamus

The pituitary gland and hypothalamus collaborate to regulate hormone production in order to maintain homeostasis. This includes the testicles, ovaries (in females), pancreas, adrenal glands, thyroid, and parathyroid glands (in males). The creation of digestive enzymes, blood pressure regulation, heart rate regulation, and fluid balance inside the body are all functions of the endocrine system.

Interaction with the pituitary gland

The hypothalamus and pituitary gland work together to secrete the following hormones:

  • Antidiuretic hormone (ADH): This hormone aids in controlling the body’s water balance. This helps to keep blood pressure stable.
  • Corticotropin-releasing hormone (CRH): By collaborating with the pituitary and adrenal glands to release specific steroids, especially in reaction to stress, this hormone helps control immune response and metabolism.
  • Follicle-stimulating hormone (FSH): FSH encourages sperm production in persons who are born as males. When a person is born a female, FSH encourages the ovaries to create oestrogen and aids in the development of the egg. An example of a gonadotrophic hormone is this.
  • Luteinizing hormone (LH): LH encourages the release of testosterone in those who were born with the gender assignment of male and female. Because it regulates the operation of the gonads—the ovaries and testes—LH is often referred to as a gonadotrophic hormone.
  • Oxytocin: Oxytocin is produced by your hypothalamus and is both stored and released by your pituitary gland. By telling their uterus to contract, oxytocin aids in the progression of labour during childbirth in persons who were assigned female at birth. Additionally, it stimulates the production of breast milk and affects parent-child bonding. Oxytocin helps sperm move in persons who are born with the gender ascribed to them as male.
  • Prolactin-controlling hormones: Dopamine and oestrogen are two such hormones that instruct the pituitary gland to either begin or stop producing breast milk in nursing women.
  • Thyrotropin-releasing hormone: The thyroid is controlled by this hormone. The thyroid controls energy levels, growth during development, and metabolism.

Growth hormones are also directly influenced by the brain. It gives the pituitary gland instructions to either raise or lower body levels, which is crucial for both developing youngsters and fully grown people.

Functions of Endocrine Gland

The level of hormones in your blood is regularly monitored by your endocrine system. In order to transmit the message, hormones send their messages by locking into the cells they intend to reach.

When your hormone levels increase, the pituitary gland signals other glands to stop manufacturing and releasing hormones. The pituitary gland has the ability to tell other glands to manufacture and release additional hormones when levels fall below a certain threshold. Homeostasis is a process that functions similarly to your home’s thermostat. Hormones have an impact on almost all bodily functions, including:

  1. Metabolism (the way you break down food and get energy from nutrients).
  2. Development and expansion.
  3. Mood and feelings.
  4. Sexual activity and fertility.
  5. Sleep.
  6. Arterial pressure

There are instances when glands create an excess or a deficit of a hormone. Health issues like weight gain, high blood pressure, and modifications in sleep, mood, and behaviour can result from this imbalance. Your body’s production and release of hormones can be influenced by a variety of factors. An imbalance in hormones can be brought on by sickness, stress, and some drugs.

Clinical Aspects of Endocrine Gland


Adenocarcinomas are malignant tumours that develop from the glandular epithelium and are prevalent in the prostate, uterus, gastrointestinal tract, lungs, and breast. They have aberrant glands that are capable of secreting mucus. They are typically identified through a biopsy, CT scan, or MRI scan. Surgery, chemotherapy, radiotherapy, or any combination of these, alone, can be used as a kind of treatment.


Adenomas, which are typically detected in the pituitary gland, are the benign counterparts of adenocarcinomas. Although pituitary adenomas do not infiltrate the tissues nearby, they can have major implications because they press against nearby structures like the optic chiasm, which can cause visual disorders. They can also release hormones like GH, which can cause acromegaly in adults and gigantism in children, or ACTH, which can cause Cushing’s illness and Cushing’s disease-related symptoms.

Gland Hyperfunction

Hormone secretion can rise in response to overactive endocrine glands such as the pituitary, thyroid, or adrenal glands. Grave’s disease, which results from the overproduction of thyroid hormones and can manifest as irritability, weight loss, tremor, and a rapid heartbeat, is an illustration of this. Surgery, radioiodine therapy, or pharmacology with drugs like carbimazole or propylthiouracil are all possible forms of treatment.

Gland Hypofunctioning

Reduced hormone production can also result from an underactive endocrine gland. Hypopituitarism, a condition in which the pituitary gland produces fewer hormones than normal, is an illustration of this. The hormones involved can cause a variety of symptoms, such as low stature (GH deficit), polyuria (ADH deficiency), and weakness (ACTH deficiency). Radiation therapy, surgery, or hormone replacement therapy are all options for treatment.

Type I diabetes mellitus, where autoimmune death of the pancreatic beta cells results in less insulin in the bloodstream, is another condition caused by hypofunction. A decrease in glucose storage might cause polyuria (increased urine) and polydipsia (increased thirst). In order to treat the condition and try to prevent consequences like diabetic nephropathy (kidney damage) and diabetic neuropathy, daily insulin injections and blood glucose monitoring are required (damage to the nerves).

FAQs on Endocrine System

Question 1: Which gland is known as the master gland?


The pituitary gland, which regulates the actions of many other endocrine glands, is sometimes referred to as the “master” gland of the endocrine system. At the base of the brain, the pituitary gland—which is no bigger than a pea—can be found.

Question 2: Which gland is known as the emergency gland?


The adrenal gland is referred to as the body’s emergency gland. When the sympathetic nervous system stimulates the adrenal medulla, adrenaline is released to help deal with stressful situations including injury, pain, fear, accident, loss, drop in blood pressure, etc. The name “emergency hormone” comes from the adrenal gland.

Question 3: How is adrenaline released?


A portion of the central nervous system’s neurons as well as the medulla of the adrenal glands create adrenaline. When faced with a stressful scenario, adrenaline is immediately released into the blood, delivering signals to various organs to elicit a certain response.

Question 4: What gland produces cortisol?


The two adrenal glands, one on top of each kidney, create the hormone cortisol. Cortisol production is regulated by the pituitary gland in the brain. An essential part of the stress response is played by cortisol.

Question 5: Where is oxytocin produced?


The hypothalamus is the primary site of oxytocin production. From there, it either travels to other regions of the brain and spinal cord where it binds to oxytocin receptors to affect behaviour and physiology, or it is released into the bloodstream via the pituitary gland.

Question 6: What are stress hormones?


The main stress hormone, cortisol, raises blood sugar levels (glucose), improves how well your brain uses it and increases the number of compounds that can be used to repair cells. Additionally, cortisol suppresses bodily processes that, in a fight-or-flight scenario, would be unnecessary or detrimental.

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Last Updated : 17 Nov, 2022
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