The human endocrine system is composed of a number of glands that are each responsible for secreting different hormones that regulate various functions within the body, including metabolism, reproduction, and growth and development.1 As such, given the variety of parts that make up this system, the possibilities for dysfunction are numerous.

Diabetes.

Diabetes is considered to be the most common endocrine disorder—at least in the United States, where more than 100 million people were reported to be living with diabetes and prediabetes in 2017.2 Diabetes is considered a disorder of the pancreas, which produces insulin, glucagon, and other hormones in healthy individuals.3 In Type 1 diabetes, which is more common in children and young adults, the body’s immune system attacks and destroys the cells in the pancreas that make insulin, leading to an inability to produce this hormone, which is responsible for regulating blood sugar.4 Conversely, in Type 2 diabetes, which is the most common type of diabetes, occurs more commonly in middle-aged or older individuals. In Type 2 diabetes, the body does not make or use insulin as efficiently as it should,4 typically due to lifestyle factors such as overweight/obesity and physical inactivity, though genes might also play a role.5 Gestational diabetes develops in some women during pregnancy due to associated hormonal changes as well as genetic and lifestyle factors, but it often disappears once the baby is born.4,5 Other less common types of diabetes include monogenic diabetes, which is an inherited form of diabetes, and cystic fibrosis-related diabetes, which can occur in adults with cystic fibrosis and shares characteristics of both Type 1 and Type 2 diabetes.4

Symptoms of diabetes include increased thirst and urination, increased hunger, fatigue, numbness or tingling in the extremities, unexplained weight loss, and sores that do not heal.5 Those with Type 1 diabetes will require insulin shots, and the needed dosages and frequencies of these shots vary from individual to individual. Other medications, such as metformin and pramlintide, might also be prescribed. Treatment for Type 2 diabetes begins with diet and physical exercise to maintain a healthy weight and good blood glucose, blood pressure, and cholesterol levels. Insulin or other medications might be also necessary depending on the individual.6

Adrenal insufficiency.

The adrenal gland produces steroid hormones (e.g., cortisol, aldosterone), and insufficient production of these hormones are considered primary, secondary, or tertiary in nature.7 Primary adrenal insufficiency, known as Addison’s disease,  occurs when the adrenal glands are damaged to the point of being unable to produce enough of the hormones cortisol and, in some cases, aldosterone.7 Secondary adrenal insufficiency stems from the pituitary gland releasing inadequate amounts of adrenocorticotropin (ACTH), a hormone that tells the adrenal glands to make cortisol. Tertiary adrenal insufficiency starts even further back in the chain with
the hypothalamus not generating enough corticotropin-releasing hormone, a hormone that tells the pituitary to make ACTH.7 Symptoms of adrenal insufficiency include chronic or long-lasting fatigue, muscle weakness, loss of appetite, weight loss, and abdominal pain, nausea, vomiting, irritability, depression, joint pain, and/or irregular or lack of menstrual periods.8 Treatment typically involves hormone replacement therapy along with, in certain cases, diet alterations.9,10

Acromegaly.

When there is an overabundance of growth hormone—produced by the pituitary gland—in the body, acromegaly can result. Acromegaly is most common in middle-aged adults and can lead to serious illness and premature death.11 Often, a benign tumor of the pituitary gland is involved, though tumors

in other areas, such as the pancreas, lungs, or parts of the brain, might also play a role.11 Related health consequences include Type 2 diabetes, high blood pressure, an increased risk of cardiovascular disease and colon polyps, and arthritis.11 Symptoms of acromegaly include aching joints; enlarged lips, nose, and tongue; excessive sweating and skin odor, as well as thick, coarse, oily skin; fatigue and weakness; headaches; impaired vision; and a deepening of the voice due to enlarged sinuses and vocal cords.11 In children affected with this condition, gigantism can occur in which excessive production of growth hormone prior to growth plate fusion results in growth and height significantly above average.11 Treatment can involve surgery, medical therapy (somatostatin analogs, growth hormone receptor antagonists, dopamine agonists), and radiation therapy.11

Thyroid dysfunction.

Hyperthyroidism and hypothyroidism are disorders of the thyroid gland and are caused by either too much (hyper) or too little (hypo) thyroid hormone production.12,13 In hyperthyroidism, symptoms include nervousness or irritability, fatigue or muscle weakness, trouble tolerating heat or sleeping, a rapid or irregular heartbeat, and mood swings, and treatment typically involves medication (e.g., beta- blockers, antithyroid drugs), radioiodine therapy, and/or surgery.12 Conversely, symptoms of hypothyroidism include weight gain, puffiness in the face, trouble tolerating cold, joint and muscle pain, dry skin and hair, decreased sweating, a slowed heart rate, and depression.13 Treatment for hypothyroidism typically involves hormone replacement therapy (levothyroxine).13 (See article on page 3 for more detailed information on hyper- and hypothyroidism.)

Hypopituitarism.

Hypopituitarism involves the disruption of pituitary gland hormone production and is characterized by deficiencies in one or a number of hormones that prompt glands throughout the body to release additional hormones.14 For this reason, hypopituitarism is especially concerning. Treatment involves the replacement of the deficient hormones.15

Polycystic ovarian syndrome (PCOS).

PCOS generally affects women of reproductive age, and symptoms include irregular menses or infertility, hirsutism (abnormal growth of hair), acne, and/or male-pattern hair loss.16 Lifestyle modifications, especially in women with overweight or obesity, represent first-line treatment, with pharmacological options also available.16 (See article on page 16 for more detailed information on PCOS.)

Precocious puberty.

Precocious puberty is an abnormally early onset of puberty in a child. Pubic hair growth, testicular enlargement, and/ or breast development and in girls younger than eight years and boys younger than nine years of age are signs of this disorder.17 While the cause of precocious puberty often isn’t known, rarely, the disorder can be attributed to infections, hormone disorders, tumors, brain abnormalities, or injuries. In children where there appears to
be no underlying cause for the development of precocious puberty, treatment usually involves injections of Gn-RH analogue, or agonist, therapy, which inhibits the release of certain pituitary hormones utilized in growth and development. In the rare cases where a cause has been identified, (e.g., a brain tumor), treatment of the underlying medical condition is necessary.17

Multiple endocrine neoplasia Type 1.

Finally, multiple endocrine neoplasia Type 1 is a rare, inherited disorder that affects both sexes equally and is characterized by hyperplasia (the enlargement of an organ or tissue) and/or neoplasm (a new and abnormal growth of tissue) of the parathyroid glands, pancreatic islets, and pituitary glands.18 Tumors can also arise in the small intestine.18 Genetic testing and/or laboratory testing to measure hormone levels is generally required for a diagnosis; there is no cure, though methods for managing the associated tumors, such as surgery, exist.18

SOURCES

1. Hiller-Sturmhöfel S, Bartke A. The endocrine system: an overview. Alcohol Health Res World. 1998;22(3):153–164.

2. United States Centers for Disease Control and Prevention site. New CDC report: More than 100 million Americans have diabetes or prediabetes. https://www.cdc.gov/media/releases/2017/p0718-diabetes-report.html. Accessed 27 Nov 2018.

3. How does the pancreas work? In: Informed Health Online [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006.

4. National Institute of Diabetes and Digestive and Kidney Diseases site. What is diabetes? www.niddk.nih.gov/health-information/ diabetes/overview/what-is-diabetes. Accessed 27 Nov
2018.