What is Endocrinology?

The branch of medicine and biology that deals with the endocrine system are called Endocrinology. This branch of medicine is also involved in the integration of health events associated with the development, growth, and differentiation of the endocrine system. It is concerned with the behavior and psychological influence, physical growth, and development caused by hormones in the endocrine system. It also covers how hormones impact a person’s tissue function, body growth development, sensory perception, mood, movement, respiration, stress, lactation, sleep, and more.

The two major specializations in this medical field are comparative and behavioral endocrinology. There are a variety of glands that make up the endocrine system. All of them are located in different areas of the body. Each secretes hormones directly into a person’s blood. These hormones are responsible for a variety of functions within the body. In some situations, a hormone may influence different organs. It’s also possible for one of the body’s organs to be influenced by several hormones. Endocrinology is the study of hormonal secretions and diseases associated with the endocrine system.

The Endocrine System

Studying the human body’s endocrine system function is also part of endocrinology. It is a system designed with glands made to secrete hormones. The hormones are chemicals able to influence the various organ systems within a person’s body.

Examples of body hormones are insulin, growth hormone, thyroid hormone, and others. This system also consists of various feedback mechanisms. This makes it possible for a hormone, such as a thyroid-stimulating hormone, to be responsible for influencing the action or release of secretions from a secondary hormone such as the thyroid hormone. Should there be too much thyroid hormone secretion, it could result in negative feedback to the thyroid-stimulating hormone. This will make it a struggle to maintain homeostasis or a body’s internal stability.


The original definition of a hormone came in 1902 and was provided by Starling and Bayliss. In their definition, a hormone is required to be a chemical that is produced by an organ in the body. It must be released in small amounts into the body. The blood must then move to a distant organ to perform its predetermined function.

This definition is applied to classical hormones. Chemical communication between cells contained within a body’s tissue or organ is known as paracrine mechanisms. Chemicals that act on the same cell where they are located are known as autocrine signals. A chemical that acts inside the same cell is known as an intracrine signal. There are neuroendocrine signal hormones. They are classified as a classical hormone and are released into the blood by a neurosecretory neuron.

Classes Of Hormones

Ojeda and Griffin were able to identify three different hormone classes. The hormones were identified based on their chemical composition.

  • Amines

Epinephrine, dopamine, or catecholamines, as well as norepinephrine, are amines. They are created with a single amino acid known as tyrosine. The subject of this class is thyroid hormones such as tetraiodothyronine or thyroxine, T4, triiodothyronine, T3. This is because these amines are created when two different iodinated tyrosine amino acid residues are combined.

  • Protein and Peptide

Protein and peptide hormones are made of three to over 200 amino acid residues. This applies in the case of the thyrotropin-releasing hormone and a follicle-stimulating hormone. They can have a molecular mass that is over 29,000 grams. The pituitary gland only secretes hormones that are a peptide. The stomach only secretes hormones ghrelin leptin from adipocytes. The pancreas only secrets insulin.

  • Steroid

The parent compound in this substance is cholesterol, which can convert to steroid hormones. These types of hormones can be categorized into five groups that are identified as mammalian steroid hormones. They are identified by the receptors they can bind with. This included progestogens, glucocorticoids, estrogens, mineralocorticoids, and androgens. Variations of vitamin D behave like an asteroid and bind to a homologous receptor. Calcitriol is one of these variations. They do not have a fused ring structure. This structure is something common with a true steroid.

The Endocrinology Profession

An endocrinologist is a medical professional. They are physicians who receive training to treat the various disorders of a person’s endocrine system. This includes hyperthyroidism, diabetes, and many other types of disorders. These medical specialists who focus on endocrinology deal with the endocrine organs. It is known that every organ in the human body responds to hormones and secretes them. This includes the kidney, brain, skin, lungs, intestines, and others. These organs in a person’s body are known for secreting hormones as their primary function. In addition, there are organs of the human body an endocrinologist can specialize in treating. They are the pancreas, pituitary, testes, thyroid, ovaries, as well as adrenals, and more.

Work Of Endocrinologist

An endocrinologist is a specialist who works in the field of endocrinology.

They will perform a diagnostic evaluation on several different physical systems when a person is experiencing health problems. They are involved in the long-term management of disorders and deficiency and the excess of one or more of the hormones in a person’s body. This also involves diagnosis and treatment of the diseases affecting the endocrine system. In addition, they will conduct laboratory tests. These tests are essential in determining their approach to diagnosis and treatment. Some types of diagnosis involve hormone stimulation or suppression.

Once this is done, blood will be sampled. It will be used to identify the changes that are relevant in metabolites as well as hormones. Those who work as an endocrinologist are required to have extensive knowledge of biochemistry as well as chemistry. This background makes it possible for them to comprehend the limitations and uses of biological investigations properly. These medical professionals are also involved with distinguishing human variations of diseases. This includes identifying a typical pattern of physical development against abnormal test results. These results are able to be carefully analyzed and show the presence or absence of disease. There may come a time when diagnostic images of a person’s endocrine organs are necessary. This is done to show any incidental findings known as incidentalomas. This could or could not represent the presence of a disease. The field of endocrinology also involves caring for an individual and the disease. Most of the disorders associated with endocrinology are chronic and will require a person to receive lifelong medical care.

There are some common endocrine diseases such as metabolic syndrome, diabetes, hypothyroidism, Mellitus, and more. To successfully address these issues, an endocrinologist needs to understand their patient on a personal and medical level. In addition, they must understand their patient on a molecular level, and the relationship between a patient and physician can also be part of an essential therapeutic process.

An endocrinologist treats patients and is also involved with hospital management, clinical science, teaching, medical research, and more.


A person who is an endocrinologist usually begins their career as a medical specialist in pediatrics or internal medicine. A reproductive endocrinologist deals with menstrual function and fertility problems. This is most often achieved after spending an amount of time first training in obstetrics. Many endocrinologists may also qualify as a gynecologist, internists, or pediatricians for a period of a few years. They can then specialize based on local training programs.

In Canada and the United States, the board-certified training in pediatrics, internal medicine, or gynecology following medical school is known as a residency.

Additional formal training is required for subspecializing in reproductive endocrinology ,pediatric and adult endocrinology, and is known as a fellowship.

The most common training for an endocrinologist in North America involves going to college for four years, attending medical school for four years, participating in three years of residency followed by two years of a fellowship.

In the United States, an endocrinologist is required to be board certified by the American Board of Internal Medicine (ABIM) or the American Osteopathic Board of Internal Medicine (AOBIM) with an emphasis on Endocrinology, Metabolism as well as Diabetes.


An endocrinologist is trained to treat diseases that affect a person’s endocrine system. This involves diseases that could be providing too much or too little necessary secretion from a hormone. There could also be too much or too little biological action from a hormone.


Essential medicines are those that provide essential health care needs of the majority of individuals within a certain population. For example, certain drugs are commonly utilized to treat disorders of the endocrine system.

It will take a physician who specializes in endocrinology to determine the type of medication to be administered and proper dosage amounts.

  • Thyroid and antithyroid medication

There is a prevalence of thyroid disorders around the world. Two of the most common medications used for their treatment are carbimazole and levothyroxine. A patient may also be treated with iodine solution in certain circumstances. This type of medication makes a person’s thyroid gland decrease its thyroid hormone production. It works faster than radioactive iodine therapy and does not permanently damage a person’s thyroid gland.

  • Androgens

This is testosterone that can be taken orally or given by injection. This can be a natural or synthetic substance able to control or stimulate the development and maintenance of male hormones.

  • Progestogen and estrogen

These are types of oral contraceptives. They can serve the majority of the needs of women during their reproductive years. There are also estrogen-only pills. They come with side effects, which have caused them to be limited in their use. A prescription for estradiol valerate in tablet form is common. There are clinical conditions that will require oral progestogens.

Some situations will also require the use of an injectable version of the hormone.

  • Insulin

This is a hormone released by a person’s pancreas. It permits the body to regulate a person’s blood sugar level properly. Medications such as glibenclamide, metformin, are often prescribed. There is also sulfonylureas, glimepiride as well as glipizide. Management of diabetes could also involve glucagon injections.

  • Adrenal drugs

These can be used to treat low adrenal function. The symptoms are lowered resistance to illness, fatigue, stress, certain skin conditions, rheumatoid arthritis, and more. In addition, there are several medications available such as adrenal hormones and synthetic substitutes. This includes medications that can be taken orally, such as dexamethasone and prednisolone.

Some medications can be injected, such as hydrocortisone sodium succinate, dexamethasone, and methylprednisolone.

  • Antineoplastic

This treatment aims to decrease the level of hormones in a person’s body. This medication could be given to a person to keep a tumor in their body from growing. They can also be used to relieve symptoms that result from having a tumor. This can also be given for thyroid cancer. Hormone therapy will be utilized if an individual’s thyroid gland has been removed. It is needed to replace the hormone secretions required by a person’s body to function properly. These are also drugs that can also be used to manage osteoporosis.

They can successfully treat bone and mineral metabolic disorders. This includes medication that comes in tablet forms such as tamoxifen citrate, prednisone, raloxifene, and prednisolone.

It’s also possible to use hydrocortisone injections when necessary. In some situations, the use of raloxifene is effective for preventing breast cancer. This is part of pharmacotherapy which is prevention therapy practiced within the endocrinology field.

Organizations and Societies

There are a number of endocrinology organizations designed to provide education to the public and patients concerning endocrinology diseases and conditions. One public education organization is the Hormone Foundation. It is an affiliate of the Endocrine Society and provides information concerning all conditions that are related to the endocrine system. Other educational organizations are focused on more than one condition related to the endocrine system.

This includes the Thyroid Foundation of America, American Diabetes Association, American Menopause Foundation, Inc., and Human Growth Foundation. The main professional organizations for endocrinologists in North America are the American Association of Clinical Endocrinologists, The Endocrine Society, The Lawson Wilkins Pediatric Endocrine Society, The American Thyroid Association, the American Diabetes Association, and others. There are also professional organizations specifically located in the United Kingdom. They include the British Society for Pediatric Endocrinology and the Society of Endocrinology. The main professional organizations in the United Kingdom are the European Society of Pediatric Endocrinology. This is the largest British internal professional association that is focused only on pediatric endocrinology. There are many organizations around the world similar to those found in North America and the United Kingdom.

Endocrinology History

China is where the earliest study of endocrinology occurred. The Chinese, by 200 BCE, were able to isolate pituitary and sex hormones from human urine. As a result, they were able to utilize them for medicinal purposes. The Chinese were able to accomplish this using a variety of complicated methods. This involved the sublimation of steroid hormones. Another method is identified in Chinese texts from as far back as 1110. It specified the use of saponin.

This is a substance taken from the beans of a Gleditschia Sinensis plant. It was utilized to extract hormones, but gypsum was also utilized. Gypsum contains calcium sulfate.

Early anatomists were able to identify most of the relevant tissues and the endocrine glands. Roman and Greek thinkers such as Galen, Celsus, Aristotle, Hippocrates, and others took a more humeral approach to comprehend the endocrine system’s complex biological functions and disease. These initial theories were the primary interpretations of endocrinology. They lasted until the 19th century. At this time, the advent of physiology and germ theory became the basis for its pathology.

In 1849, it was noted by Arnold Berthold that cockerels that had been castrated weren’t able to develop wattles, combs as well as exhibit specific behavior assigned to a male.

Berthold discovered that replacing testes back into the abdominal cavity of a castrated cockerel resulted in the increased morphological development of behavior.

Berthold was wrong when he concluded the cockerel testes secreted a substance that conditioned the blood and then influenced the body of the cockerel. Current experts agree two other things may have been true. One was that the testes were modified, which caused the activation of a constituent of the blood. The other is that the testes eliminated the inhibitory factor from the cockerel’s blood. Berthold did not prove that the cockerel’s testes released a substance that endangered its male characteristics. It was eventually proven the extract of the testes was able to replace their function within a castrated animal.

Historical Milestones

Robert James Graves was an Irish doctor in 1835. He identified a case of goiter with exophthalmos. The Graves’ disease was named after him. Similar constellations of the disease were independently reported in 1840 by a German named Karl von Basedow. There were earlier reports of this disease that two Italians published.

In 1802 by Giuseppe Flajani and 1810 by Antonio Guiseppe Testa. In the late 18th century, an English doctor named Caleb Hillier Perry also published a report on the disease. Then, in 1849, Addison’s disease was first described by Thomas Addison.

Ernest Starling and William Bayliss, in 1902, performed a significant experiment concerning this disease. They observed when the duodenum had acid instilled into the pancreas, secretion began. This occurred even after all nerve connections between the duodenum and pancreas had been severed. The same response occurred with an extract of jejunum mucosa was injected directly into a jugular vein. This was proof that some substance of the mucosa was responsible.

This substance was called secretin. It started the term hormone for chemicals that behaved in this manner. An observation was made in 1889 that the surgical removal of a pancreas increased blood sugar. A coma followed this, and eventually, death occurred. These were symptoms of diabetes mellitus. This was done by Oskar Minkowski and Joseph von Mering. The act of homogenizing the pancreas and injecting it with a derived extract, which resulted in the condition being reversed, happened in 1922 by scientists Best and Banting.

In 1953, the hormone that made insulin possible was discovered by Frederick Sanger, who was able to sequence it. In 1921, Otto Loewi identified Neurohormones. To do this, Loewi incubated a frog’s heart using a saline bath. The frog’s heart was left in the solution for an extended period. The resulting solution was utilized for bathing a second heart that was non-innervated. The goal was for the vagus nerve on the first heart to be simulated and react with a beat amplitude and the beat rate activity to the second heat. This activity occurred with both hearts. Such activity did not happen if either heart had the vagus nerve not stimulated. It was obvious the vagus nerve was providing something in the saline solution. This result could be stopped with the use of atropine. This proved to inhibit stimulation of the heart’s vagus nerve. Obviously, something was being given off by the vagus nerve and causing the heart’s reaction. Loewi referred to this as vagus stuff. It caused muscle-enhancing effects that eventually were called norepinephrine and acetylcholine. This discovery earned Loewi the Nobel Prize in 1936.

Recent Work

The focus of recent work in the field of endocrinology is on molecular mechanisms and their ability to trigger effects on hormones. Earl Sutherland started this type of work in 1962. He studied whether hormones would go into cells and begin the action or remain outside the cells. Sutherland investigated norepinephrine. This causes a reaction in the liver and converts glycogen into glucose utilizing the activation of the enzyme phosphorylase. The liver was homogenized into an insoluble fraction and membrane fraction by Sutherland.

Norepinephrine was then added to the membrane fraction. Soluble products were then extracted and then added to the initial soluble fraction. Phosphorylase was activated, indicating that the receptor targeted by norepinephrine was on the membrane of the cell. It was not located intracellularly.

Sutherland later identified this compound as cyclic AMP. This discovery created the idea of second-messenger-mediated pathways. This work was considered groundbreaking in the field of endocrinology. Earl Sutherland was awarded the Nobel Prize for it in 1971.

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