What Is an Endocrinologist?

In-Demand Specialty Devoted to Hormonal Disorders

An endocrinologist is a physician who specializes in endocrinology, a branch of medicine devoted to the study of hormonal glands and the diseases and disorders that affect them. The specialty involves the evaluation of a wide range of symptoms in relation to a deficiency or excess of hormones. Many of these conditions are chronic (meaning they persist over a long time) and require ongoing and even lifelong management.

Endocrinologist taking ultrasound
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An endocrinologist is first trained in internal medicine, pediatrics, or gynecology before specializing in endocrinology. In the United States, the typical training involves four years of college, four years of medical school, three years of residency, and two years of fellowship.

Endocrinologists are in high demand, with fewer than 4,000 actively practicing in the United States, according to a 2014 study in the Journal of Clinical Endocrinology and Metabolism.


Endocrinology is a subspecialty of internal medicine whose function is to evaluate how hormones can affect metabolism, growth, weight, sleep, digestion, mood, reproduction, sensory perception, menstruation, lactation, and organ function, among other things.

Although every organ system secretes and responds to hormones, endocrinology focuses primarily on the organs of the endocrine system, specifically

  • Adrenal glands, two glands situated atop the kidneys that secrete cortisol, the body's primary stress hormone, and aldosterone, which regulates blood pressure and sodium levels
  • Hypothalamus, a part of the lower middle brain that tells the pituitary gland when to release hormones
  • Ovaries, the female reproductive organs that produce female sex hormones
  • Pancreas, an organ in the abdomen that secretes the hormones insulin and glucagon
  • Parathyroid, four glands in the neck that play a key role in bone development and calcium regulation in the blood
  • Pineal gland, a gland in the center of the brain that helps regulate sleep patterns
  • Pituitary gland, often called the "master gland" because it influences the function of all other glands.
  • Testes, the male reproductive glands that produce male sex hormones
  • Thymus gland, an organ in the upper chest that influences the development of the immune system early in life
  • Thyroid gland, a butterfly-shaped organ in the neck that regulates metabolism

Any dysfunction of these organs can influence how much or little of a hormone is produced. Moreover, because the endocrine organs influence each other, the dysfunction of one organ can have a knock-on effect and trigger multiple hormonal imbalances.

Conditions Treated

Endocrine disorders may be caused by disease, injury, infection, or benign or cancerous growth. There are also genetic disorders that can affect the normal function of a gland. Failures in the endocrine feedback loop (the system in which endocrine glands respond to external stimuli or each other) can also lead to imbalances.

Among the conditions an endocrinologist can treat (or participate in the treatment of):

Depending on the condition, an endocrinologist may work alone or with other medical professionals, including gynecologists, neurologists, oncologists, osteopathic surgeons, pediatricians, and primary care physicians.

Procedural Expertise

If you have been referred to an endocrinologist, it is usually because there are indications (either through lab results or symptoms) of a hormonal disorder. Endocrinologists are rarely your first point of contact for a medical condition and almost never work as primary care physicians.

Endocrinology is unique in that the diagnosis and treatment of endocrine diseases are guided more by lab tests than almost any other medical specialty.


Blood and urine tests are standardly used to measure hormone levels in blood or urine samples. Others tests involve the injection of a stimulating or inhibiting agent to see how an endocrine gland reacts. In addition to blood tests, the endocrinologist may order imaging studies and other procedures to get an up-close look at a gland.

Among some of the tests commonly ordered by an endocrinologist:

  • 24-hour urine collection, which provides a more accurate picture of the hormone levels in the body, including cortisol
  • ACTH stimulatory test, which uses an injection of adrenocorticotropic hormone (ACTH) to help diagnose adrenal disorders
  • Computed tomography (CT), a type of computer-assisted X-ray that creates three-dimensional "slices" of internal structures
  • CRH stimulation test, which uses an injection of corticotropin-releasing hormone (CRH) to check for adrenal disorders
  • Dexamethasone suppression test, which uses an injection of synthetic cortisol to check for Cushing's disease
  • Fine needle aspiration (FNA) biopsy, in which a needle is inserted into the thyroid gland or tumor to extract cells for microscopic evaluation
  • Magnetic resonance imaging (MRI), which uses powerful magnetic and radio waves to create highly detailed images, particularly of the pituitary gland.
  • Metaiodobenzylguanidine (MIBG) scan, sometimes used to detect metastatic cancers
  • Oral glucose tolerance test, in which you drink a sweet glucose drink to help diagnose diabetes
  • Dotatate scan, in which a radioisotope, gallium 68, is injected into the body and binds to somatostatin receptors that are highly expressed in most neuroendocrine tumors. 
  • Positron emission tomography (PET), an imaging test that uses a radioactive substance to identify metabolic abnormalities seen in most cancers
  • Radioactive iodine scan (RAI), used for detecting normal and cancerous cells in the thyroid gland
  • Ultrasound, both abdominal and endoscopic, which uses sound waves to detect masses or fluid in soft tissues
  • Venous sampling, which involves the insertion of a catheter into a vein to extract blood from a specific part of the body for hormone testing


The treatments used in endocrinology are as far-ranging as the diseases involved. Many disorders can be treated with hormone replacement therapies (HRT) that use either oral or injected drugs to overcome diagnosed deficiencies. Among them:

  • Glucocorticoid pills can replace hormones in people with malfunctioning adrenal or pituitary glands.
  • Growth hormone therapy, involving injections of growth hormone (GH), is sometimes used to treat growth disorders in children and GH deficiencies in adults.
  • Hormonal birth control can be used to treat PMS, PCOs, and endometriosis or prevent postmenopausal osteoporosis.
  • Insulin and other diabetes drugs can help normalize blood sugar in people with diabetes.
  • Testosterone replacement, involving injections, patches, pills, and gel, can be used in people with low testosterone (hypogonadism) in men or women.
  • Thyroid replacement drugs, including Synthroid (levothyroxine) and Cytomel (liothyronine), may be used to restore thyroid function in people with hypothyroidism.

In other instances, surgery and other procedures may be required to correct an endocrine disorder. Examples include:

  • Adrenalectomy, a surgical procedure to remove the adrenal gland in cases of cancer or Cushing's disease
  • Gamma knife radiosurgery, a type of surgery involving around 200 beams of radiation to precisely extract tumors, including those in the hypothalamus
  • Radioiodine ablation, which uses radioactive iodine to destroy residual tissue after a thyroidectomy
  • Thyroidectomy, a surgical procedure to remove all or part of the thyroid gland in cases of thyroid cancer, thyroid nodules, and hyperthyroidism.


Because endocrinology is such a vast and diverse field, some endocrinologists will choose to limit their practice to specific conditions, populations, or procedures. Examples include:

  • Diabetes and metabolism
  • Endocrine oncology (involving cancer)
  • Endocrinology nuclear medicine
  • Gender reassignment
  • Neuroendocrinology
  • Pediatric endocrinology
  • Reproductive endocrinology (a.k.a. fertility specialists)
  • Thyroid disease

Training and Certification

Endocrinologists are physicians and therefore must obtain a medical degree as either a doctor of medicine (MD) or doctor of osteopathic medicine (DO). The first two years of medical school are primarily devoted to classroom studies. The final two years involve clinical rotations in different hospitals to gain exposure to the various fields of medicine.

Upon completion of medical school, graduates must pass the United States Medical Licensing Exam (USMLE) to obtain a license in the state in which they choose to practice. Thereafter, they would begin their postdoctoral training by completing a three-year residency in internal medicine, pediatrics, or gynecology.

Near the end of the residency, the endocrinology candidate would apply for a two- to three-year fellowship in endocrinology. Fellowship programs can vary, with some providing general training. while others focus on pediatrics or reproduction and infertility. Endocrinologists are required to be board certified by the American Board of Internal Medicine (ABIM). The peer-reviewed exams are comprised of written tests.

In order to renew a medical license, an endocrinologist must participate in continuing medical education (CME) programs and maintain a certain number of study hours. Depending on the state and medical subspecialty, licenses are renewed every seven to 10 years.

Appointment Tips

if you have been referred to an endocrinologist, it is because a hormonal disorder or an associated condition is beyond the scope of practice of the referring doctor.

To get the most out of your appointment, arrive early and bring along any lab tests or imaging studies relevant to your condition. You should also ask the referring doctor to forward any pertinent files in advance of your appointment.

The appointment would generally start with an extensive review of your symptoms, medical history, family history, and any medications you are taking. It often helps to write these things down in advance to avoid forgetting or overlooking them.

To get a better understanding of your condition and what tests and treatments are involved, don't be afraid to ask as many questions as you need. They might include:

  • What experience have you had treating this condition?
  • How much of your practice devoted to this condition?
  • What should I expect once I start treatment?
  • What are the possible risks and complications?
  • What is the success rate for the treatment?
  • When might I know if the treatment is successful?
  • Will the treatment affect my ability to work?
  • Who do I call if there is a problem, even at night?
  • Is there anything I can do improve my condition?
  • What might happen if I choose not to be treated?
  • Are there any alternatives I should consider?

To find a certified endocrinologist, check the ABIM verification portal.

Finally, don't forget to check whether the endocrinologist and lab are in-network providers with your insurance company. If not, you will almost certainly pay more and, in some cases, the entire billing amount.

A Word From Verywell

Endocrinologists often choose the profession because it doesn't involve just one organ system or disease. Instead, endocrinology looks at the interrelationship between multiple organs and how they each contribute to disease. The profession demands three-dimensional thinkers who are naturally curious and able to look at a problem from all sides.

The practice itself typically operates during regular office hours. Most tests and procedures are conducted in-office. Unless the practitioner specializes in surgery or cancer treatment, the more invasive procedures are standardly referred to an outside specialist.

According to the annual Medscape Compensation Report, endocrinologists in the United States earned a median income of $212,000 in 2018. Roughly 73% operate private practices in a profession largely dominated by women.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

By Andrea Clement Santiago
Andrea Clement Santiago is a medical staffing expert and communications executive. She's a writer with a background in healthcare recruiting.