Endocrinology is the field of hormone-related diseases. An endocrinologist can diagnose and treat hormone problems and the complications that arise from them.

Hormones regulate metabolism, respiration, growth, reproduction, sensory perception, and movement. Hormone imbalances are the underlying reason for a wide range of medical conditions.

Endocrinology focuses both on the hormones and the many glands and tissues that produce them.

Humans have different hormones. They can exist in very small amounts and still have a significant impact on bodily function and development.

Fast facts on endocrinology

Here are some key points about endocrinology. More information is in the main article.

  • Endocrinology involves a wide range of systems within the human body.
  • The endocrine tissues include the adrenal gland, hypothalamus, ovaries, and testes.
  • There are three broad groups of endocrine disorders.
  • Polycystic ovary syndrome is the most common endocrine disorder in women.

The human endocrine system consists of a number of glands, which release hormones to control many different functions.

When the hormones leave the glands, they enter the bloodstream and are transported to organs and tissues in every part of the body.

Adrenal glands

Endocrinology
Endocrinology refers to a medical focus on hormones. Hormones shape the body and drive its systems.

The adrenal, or suprarenal, glands are located on top of the kidneys. They are divided into two regions. The right gland is triangular, and the left is crescent-shaped.

The adrenal glands secrete:

Both men and women have some androgen, but men have higher levels. Androgens control the development of characteristics associated with males, like facial hair and a deeper voice.

Hypothalamus

The hypothalamus is located just above the brain stem and below the thalamus.

This gland activates and controls involuntary body functions, including respiration, heart rate, appetite, sleep, temperature, and the circadian cycles, or daily rhythms.

The hypothalamus links the nervous system to the endocrine system via the attached pituitary gland.

Ovaries and testicles

The ovaries are located on either side of the uterus in females. They secrete the hormones estrogen and progesterone.

These hormones promote sexual development, fertility, and menstruation.

The testicles are located in the scrotum, below the penis in males. They secrete androgens, mainly testosterone.

Androgens control sexual development, puberty, facial hair, sexual behavior, libido, erectile function, and the formation of sperm cells.

Pancreas

Located in the abdomen, the pancreas is both an endocrine gland and a digestive organ.

It releases:

  • Insulin: Important for carbohydrate and fat metabolism in the body
  • Somatostatin: Regulates endocrine and nervous system function and controls the secretion of several hormones, such as gastrin, insulin, and growth hormone
  • Glucagon: A peptide hormone that raises blood glucose levels when they fall too low
  • Pancreatic polypeptide: This helps control the secretion of substances made by the pancreas

Diabetes and digestive issues can result if there are problems with the pancreas.

Parathyroid glands

  • These small endocrine glands located in the neck produce parathyroid hormone, which regulates calcium and phosphate in the blood.
  • Muscles and nerves can only operate safely and effectively if these chemicals are at the correct levels.

Pineal body, or pineal gland

This is a small endocrine gland located deep in the brain. It secretes melatonin and helps control the body's sleep patterns and moderate levels of reproductive hormones.

Pituitary gland

An endocrine gland attached to the hypothalamus at the base of the brain.

It is sometimes called the main endocrine master gland because it secretes hormones that regulate the functions of other glands, as well as growth and several other bodily functions.

The anterior, or front, pituitary secretes hormones that affect sexual development, thyroid function, growth, skin pigmentation, and adrenocortical function.

If the anterior pituitary is underactive, it can lead to stunted growth in childhood and underactivity in other endocrine glands.

The posterior, or rear, pituitary secretes oxytocin, a hormone that increases contractions of the uterus and antidiuretic hormone (ADH) which encourages the kidneys to reabsorb water.

Thymus gland

The thymus is an endocrine gland located beneath the breastbone, or sternum.

T lymphocytes, a type of immune cell, mature and multiply in the thymus gland early in life. After puberty, the gland shrinks.

The thymus gland plays a role in the immune system, which protects the body against disease and infection.

Thyroid gland

A butterfly-shaped gland located just below the Adam's apple in the neck, the thyroid produces hormones that play a key role in regulating blood pressure, body temperature, heart rate, metabolism, and how the body reacts to other hormones.

The thyroid gland uses iodine to create hormones.

The two main hormones it produces are thyroxine and triiodothyronine.

It also produces calcitonin, which helps strengthen bones and regulates the metabolism of calcium.

Below is a 3-D model of the endocrine system, which is fully interactive.

Explore the model using your mouse pad or touchscreen to understand more about the endocrine system.

A hormone imbalance can result from genetic or environmental factors.

Some infants are born with hormonal problems that can lead to a range of health issues, such as low growth.

Endocrine-disrupting chemicals, such as pesticides, lead, and phthalates, which are used in plastic food containers, can sometimes lead to hormonal problems.

There are three broad groups of endocrine disorders:

What can go wrong?

Here are some examples of what can happen if a gland secretes too much or too little of its hormones.

Adrenal Gland

Pancreas

  • Hypersecretion may lead to hyperinsulinism, too much insulin can lead to low blood glucose
  • Hyposecretion may lead to one type of diabetes

Parathyroid Gland

  • Hypersecretion may lead to brittle bones that fracture easily, as well as stones in the urinary system
  • Hyposecretion may lead to involuntary muscle contractions, or tetany, caused by low levels of calcium in plasma

Thyroid Gland

Pituitary Gland

  • Hypersecretion may lead to gigantism, or excessive growth
  • Hyposecretion may lead to slow bone growth and short stature

Thymus Gland

  • Hypersecretion may lead to an overactive immune system which overreacts to perceived threats. This may result in an autoimmune disease.
  • Hyposecretion may lead to a weakened immune system, where the body is unable to fight infection and easily succumbs to viruses, bacteria, and other pathogens.