Endocrinology deals with the diagnosis and treatment of diseases that involve hormones; it covers a number of topics, including controlling metabolism, respiration, growth, reproduction, sensory perception, and movement.
Endocrinology also focuses on the many glands and tissues that produce hormones.
In this article, we will discuss the role that the endocrine system plays and what happens when it is affected by disease. We will also explain what might happen during an appointment with an endocrinologist.
Contents of this article:
Fast facts on endocrinology
Here are some key points about endocrinology. More detail and supporting information is in the main article.
- Endocrinology covers a vast array 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
What is the endocrine system?
The endocrine system affects every part of the human body.
The human endocrine system consists of a number of glands. These glands make and secrete (release) hormones which 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 (suprarenal glands)
The adrenal 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.
They also release catecholamines, such as norepinephrine and epinephrine, these are released in response to stress.
In addition, the adrenal glands produce androgens, which are male sex hormones and include testosterone. Androgens control the development of male characteristics, like facial hair and a deeper voice.
Another product of the adrenal glands is aldosterone, which affects kidney function.
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 (daily rhythms).
The hypothalamus links the nervous system to the endocrine system via the pituitary gland, which is attached to it.
Ovaries and testicles
The ovaries, located on either side of the uterus in females, secrete the hormones estrogen and progesterone. These hormones promote sexual development, fertility, and healthy menstrual periods.
The testicles, located in the scrotum, below the penis in males, secrete androgens, mainly testosterone. Androgens control sexual development, puberty, facial hair, sexual behavior, libido, erectile function, and the formation of sperm cells (spermatogenesis).
Located in the abdomen, the pancreas is both an endocrine gland and a digestive organ. It releases the following products:
- Insulin - plays a key role in 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 which raises blood glucose levels when they fall too low
- Pancreatic polypeptide - helps control the secretion of substances made by the pancreas
These are small endocrine glands located in the neck. They produce parathyroid hormone, which regulates calcium and phosphate in the blood. Muscles and nerves can only operate if these chemicals are at the correct levels.
Pineal body (pineal gland)
The pineal is a small endocrine gland located deep in the brain. It secretes melatonin and helps to control the body's sleep patterns and moderate levels of reproductive hormones.
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 body functions.
- The anterior (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 (rear) pituitary secretes oxytocin, a hormone that increases contractions of the uterus and ADH (antidiuretic hormone) which encourages the kidneys to reabsorb water.
The thymus is an endocrine gland located beneath the breastbone (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 body's immune system.
An endocrine gland located just below the Adam's apple in the neck; it 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 manufacture hormones. The two main hormones it produces are thyroxine and triiodothyronine. The thyroid gland also produces calcitonin, which helps strengthen bone and regulates the metabolism of calcium.
There are three broad groups of endocrine disorders:
- Endocrine gland hyposecretion - when a gland is not producing enough hormones
- Endocrine gland hypersecretion - when a gland is overactive and producing too much hormones
- Tumors of endocrine glands - these may be malignant (cancerous) or benign (non-cancerous)
Below are some examples of what may occur if a gland secretes too much or too little of its hormones:
- Hypersecretion may lead to over-nervousness, sweating, raised blood pressure, and Cushing's disease
- Hyposecretion may lead to Addison's disease, Mineralocorticoid deficiency, weight loss, loss of energy, and anemia
- Hypersecretion may lead to hyperinsulinism, too much insulin can lead to low blood glucose
- Hyposecretion may lead to diabetes
- Hypersecretion may lead to brittle bones that fracture easily, as well as stones in the urinary system
- Hyposecretion may lead to involuntary muscle contractions (tetany), caused by low levels of calcium in plasma
- Hypersecretion is most often caused by Graves' disease, accelerated metabolism, sweating, arrhythmia (irregular heart beat), weight loss, and nervousness
- Hyposecretion may lead to tiredness, weight gain, depression, abnormal bone development, developmental delay, and stunted growth
- Hypersecretion may lead to gigantism (excessive growth)
- Hyposecretion may lead to slow bone growth and very short stature
- Hypersecretion may lead to an overactive immune system
- Hyposecretion may lead to a weakened immune system
- Hypersecretion may lead to exaggerated female traits
- Hypersecretion may lead to exaggerated male characteristics
Polycystic ovary syndrome
PCOS is a relatively common endocrine disorder, but the causes are still unknown.
Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women.
Women with PCOS have larger than normal ovaries that contain a number of small, fluid-filled sacs, called follicles. The three main features are as follows:
- Irregular periods - fewer than eight periods a year, or cycles longer than 35 days.
- Excess Androgen - elevated levels of the male hormone, androgen. This can cause excess hair, acne, and sometimes baldness.
- Polycystic ovaries - fluid-filled sacs within the ovaries.
The causes are not yet fully understood, and unfortunately there is no cure. Treatment revolves around hormonal medications, weight loss, and managing the symptoms.
What happens during a visit to an endocrinologist?
A doctor who specializes in endocrinology is an endocrinologist. They are trained to diagnose diseases that affect the glands mentioned above.
An endocrinologist diagnoses and treats hormone problems by attempting to restore hormone balance within the body's systems. The following diseases or disorders are commonly treated by endocrinologists:
- Metabolic disorders
- Thyroid diseases
- Excessive or insufficient production of hormones
- Some cancers
- Short stature
The first visit to an endocrinologist will involve a conversation where the patient will be asked a number of questions to help the doctor work out what might be wrong. The questions might cover:
- Current medications
- Family history of hormonal problems
- Other medical conditions including allergies
- Dietary habits
It is a good idea to compile a list of any existing symptoms before the visit, so that none are missed. The endocrinologist might ask questions about symptoms that do not seem to be related, or that seem unnecessary. This is because hormone levels affect so many different systems in the body that just small changes in one gland can impact parts of the body far from the site of the glands themselves.
The endocrinologist will check heart rate and blood pressure, and look for signs of dry skin. They may also inspect the patient's hair, teeth, and mouth. Blood and urine samples are often taken.