Endocrinology - What is Endocrinology?

Clinical endocrinology is a branch of Medicine that deals with the endocrine glands, actions of hormones and their metabolic consequences.

Since hormones act on virtually every organ and cell type in the body, the endocrinologist needs to have a definitive knowledge about medicine.

Some disorders lie very clearly and totally within the domain of the endocrinologists, being entirely or largely due to an abnormality of hormone production. This includes diabetes that is caused due to decreases secretion of insulin from pancreas (Type 1 diabetes) or hypothyroidism that is caused due to decreased secretion of thyroid hormone from the thyroid glands.

Yet other diseases are not exactly of endocrine origin but have aspects of endocrinology in them. This includes examples such as osteoporosis or infertility. In these cases the endocrinologist may need to work with a physician or a gynaecologist and a multidisciplinary approach is appropriate.

History of endocrinology

History of endocrinology and study of hormone function dates back to 400 BC when Hippocrates brought forth the Humoral Hypothesis. Aristotle noted there were changes in physical and behavioral aspects after castration on roosters.

It was noted that pre-pubertal castration in humans led to short stature, long arms, no facial hair or pubertal change in voice. These eunuchs guarded the doors of the queens and noble women in ancient times.

17th and 18th century common practices

Once a common practice in Europe and Asia involved castrating young boys with singing voices to prevent the pubertal changes in voice and use them as choir boys. Popularity reached a peak in 17th and 18 centuries. These boys were called Castrati and had a range of a soprano, but greater development of the male lungs meaning more power.

The first recorded hormone experiments

The first recorded endocrine experiment and noted researchers who were experimenting with hormones and circulation were William Harvey (1628), John Hunter (late 1600’s) and Bordeau (1775). Arnold Berthold conducted the first experiment showing constancy of the Internal Environment.

Claude Bernard

Claude Bernard (in 1872) found that a regulated internal environment (le milieu intérieur) in a changing, and challenging, environment was noteworthy. He noted that cells and tissues need to communicate for coordination of physiological activities.

Charles Brown-Séquard

Charles Brown-Séquard, a French physician, first studied Endocrine Replacement Therapy or replacement of deficient hormones within the body by supplementing it from outside. Von Mering and Menkoski removed the pancreas from dogs and noticed changes in urine and blood glucose.

The first described hormone

The first described hormone (1902) was a result of efforts by Sir William Bayliss (1860-1924) and Ernest Starling (1866-1927). In response to the delivery to the intestine of acidic chyme from the stomach, endocrine cells of the duodenun release secretin (an internal secretion) into the bloodstream.

The researchers found that Secretin stimulates the exocrine pancreas to secrete bicarbonate into the intestine to neutralize the acid. In 1902 epinephrine was purified and it was synthesized in 1904.


Between 1900 and 1930’s was a period of research on biochemistry, reproductive cycles, and surgery. In 1920-1930 Adrenalectomy (removal of adrenal glands) and hypophosectomy (removal of pituitary glands) were perfected and all steroid hormones were discovered.


In 1940-1950 radioisotopes, culturing methods, electron microscope were used in experiments. Between 1950’s and 1960’s detailed biochemistry and mechanisms of action were studied.

Endocrinology achievements

  • Frederick Sanger determined the structure of insulin (1958) and this was a landmark achievement in endocrinology. Hormone Structure, Synthesis and Assay was perfected.
  • Vincent du Vigneaud synthesized polypeptide hormones (oxytocin and vasopressin) in 1955.
  • Rosalyn Yalow developed radioimmunoassay for measurement of hormone concentrations in 1977.
  • Katsoyannis synthesized insulin in 1963.

Endocrinology today

At present endocrinology deals with major aspects like:

  • Scientific – Dealing with discovery and assaying the structures and functions of various hormones
  • Clinical – This deals with the clinical disorders of endocrine system and their complex pathophysiology and management.
  • Food Production – Endocrinology and genetic engineering in conjunction are being widely used in increasing animal produce like meat, eggs, milk etc.

Endocrinologist - What is an Endocrinologist?

Endocrinology is a complex study of the various hormones and their actions and disorders in the body. Glands are organs that make hormones. These are substances that help to control activities in the body and have several effects on the metabolism, reproduction, food absorption and utilization, growth and development etc.

Hormones also control the way an organism responds to their surroundings and help by providing adequate energy for various functions.

The glands that make up the endocrine system include the pineal, hypothalamus, pituitary, thyroid, parathyroid, thymus, adrenals, pancreas, ovaries and testes.

Who is an endocrinologist?

An endocrinologist is a specially trained doctor who has a basic training in Internal Medicine as well.

Some disorders like low thyroid hormone production or hypothyroidism deals only with an endocrine organ and an endocrinologist alone may detect, diagnose and manage such patients.

Yet other disorders may have endocrine as well and other origins like infertility and may need a deeper understanding of medicine on the part of the endocrinologist to identify and work in collaboration with another specialist (a gynaecologist in cases of infertility).

What do endocrinologists do?

Endocrinologists have the training to diagnose and treat hormone imbalances and problems by helping to restore the normal balance of hormones in the body. The common diseases and disorders of the endocrine system that endocrinologists deal with include diabetes mellitus and thyroid disorders.

Diabetes mellitus

This is one of the most common conditions seen by endocrinologists. This results due to inadequate insulin hormone secreted by the pancreas leading to excess blood sugar that damages various organs.

Endocrinologists treat diabetes with diet and blood sugar reducing medications, including insulin. They also work closely with patients to control blood sugar and monitor them so they can prevent health problems.

Thyroid disorders

This could be an overactive thyroid or hyperthyroidism or underactive thyroid or hypothyroidism.

Endocrinologists treat patients reach a hormone balance by replacing or blocking thyroid hormone depending on whether there is hypo or hyperthyroidism.

Other common diseases and disorders that endocrinologists manage

  • Metabolic diseases
  • Menopause and its hormonal unbalances
  • Over- or underproduction of hormones
  • Osteoporosis and vitamin D deficiency leading to osteomalacia and rickets in children
  • Infertility
  • Precocious puberty
  • Lack of growth (short stature)
  • Pediatric endocrine diseases
  • Excessive growth or acromegaly/gigantism
  • Cancers of the endocrine glands
  • High blood pressure due to endocrine dysfunctions like adrenal gland tumors pheochromocytoma
  • High blood cholesterol or lipid abnormalities associated with heart disease

Training for endocrinologists

Endocrinologists need four years of medical school and then spend three or four years in an internship and residency program. They cover internal medicine, pediatrics, or obstetrics and gynecology during this time.

Thereafter they spend two or three more years learning how to diagnose and treat hormone conditions.

Core training requires knowledge of normal physiology of the endocrine system, including the physiology and biochemistry of hormones, and their actions. Extensive first-hand practical experience in a recognised training centre, of the management of diseases primarily involving the endocrine system follows.

Diabetes specialism

Those training to further specialize in diabetes need experience in eye, blood vessel and kidney diseases associated with diabetes. They need to train in diabetic foot care to prevent gangrene of diabetic foot and amputation of the limbs.

Special training in managing pregnant women, children and adolescents with diabetes and care of the diabetic patient undergoing surgery is needed.

Diabetes education, diet advice, exercises regimens for general masses are also a part of the training. They need to identify and treat obesity and anorexia nervosa, lipid disorders, metabolic bone disease and calcium disorders and fluid and electrolyte disorders.

There is an increasing proliferation of tests and new therapeutic procedures. Thus, the endocrinologist often has an important role in defining the most efficient and cost-effective strategy for their use in patient care. To the practising endocrinologist, laboratory measurement of circulating hormone levels is crucial. Training should therefore include practical experience in an endocrine laboratory. An endocrinologist has access to an up-to-date hormone assay service.

Multidisciplinary training

Several areas need to be accessible in the training of endocrinologists. These include:

  • Growth disorders, and disorders of stature with paediatric endocrinologists  
  • Reproductive endocrinology with gynaecologists in development of the understanding of an endocrine basis of infertility with use of gonadotrophic stimulation therapy and assisted reproduction
  • Surgical endocrinology for management of pituitary, thyroid, adrenal tumors operatively
  • With radiologists, radiotherapists and nuclear medicine specialists for diagnostic and therapeutic uses and imaging techniques relevant to endocrinology, such as ultrasound
  • With oncologists for cancers of the endocrine system

Organizations for endocrinologists

American professional organizations for endocrinologists include:

  • The Endocrine Society
  • the American Association of Clinical Endocrinologists
  • the American Diabetes Association
  • the Lawson Wilkins Pediatric Endocrine Society
  • the American Thyroid Association

The main professional organisations in United Kingdom include:

  • The Society for Endocrinology and the British Society for Paediatric Endocrinology and Diabetes
  • European Thyroid association

For pediatric endocrinology the organization revered internationally is the European Society for Paediatric Endocrinology. This is not an exhaustive list and there are more organizations worldwide.