General Information About Hormones

Hormones are chemical messengers produced by the endocrine glands that regulate various physiological processes in the body, including growth and development, metabolism, and reproductive function. They travel through the bloodstream to target cells and tissues, where they bind to specific receptors and trigger a response. Examples of hormones include insulin, thyroid hormones, and estrogen.

The word “hormone” comes from the Greek word “hormōn,” meaning “to set in motion.” The earliest researchers of hormones were scientists in the late 19th and early 20th centuries, such as the French physiologist Charles-Édouard Brown-Séquard and the German physiologist Oswald Schmiedeberg. They both discovered that extracts of animal organs could have physiological effects on other animals.

The term “hormone” was coined by British physiologist William Bayliss and his colleague Ernest Starling in 1905. Bayliss and Starling used the term to describe the chemical messenger substance produced by the pancreas that regulates blood sugar levels, which they named secretin.

Later on, endocrinology as a field of study began to take shape with the work of physicians and scientists such as Edward Adelbert Doisy, who isolated and determined the structure of the hormone estrogen and won the 1943 Nobel Prize in Physiology or Medicine.

What are Hormones?

Endocrine system glands create hormones, which are chemical messengers. They travel through the bloodstream to different human organs and tissues where they act on particular receptors to control a range of physiological functions, including growth, metabolism, and reproduction.

The equilibrium of the body’s internal environment, known as homeostasis, is crucially maintained by hormones. Additionally, they are crucial in controlling behavior and mental functions like mood, hunger, and stress response.

Numerous physiological processes in the body can be controlled by hormones acting alone, in combination with other hormones, or in conjunction with neurotransmitters.

Hormones are essential for the growth and development of living things. They perform the function of chemical messengers that control a number of physiological processes, including growth, metabolism, and reproduction. Steroid hormones, peptide hormones, and protein hormones are the three main subtypes of hormones.

They are created by specialized cells and tissues in the body and are then sent to target cells or tissues via the bloodstream, where they attach to particular receptors and cause a response.

The term “hormone” has a very broad definition and refers to a variety of signaling molecules produced by different human organs and tissues that have effects elsewhere in the body. In addition to the conventional hormones produced by the endocrine system’s glands, this also refers to hormone-like compounds made by the brain, immune cells, and even the gut.

For example, hormones like adrenaline and noradrenaline are produced by the adrenal glands, but also by certain neurons in the brain. Cytokines, which are produced by immune cells, can also act as hormones by signaling to other cells in the body to coordinate an immune response. Peptide hormones, neurotransmitters, and even steroids can also act as hormones.

This broad definition of a hormone highlights the complexity and interconnectivity of the different physiological systems in the body, and how different molecules can act in concert to regulate various physiological processes.

The different types of molecules that can be classified as hormones are quite diverse.

Eicosanoids are a type of hormone that are derived from fatty acids and include prostaglandins and thromboxanes. They are involved in a wide range of physiological processes, such as blood clotting, inflammation, and pain perception.

Steroids are another type of hormone that include hormones like estrogen and testosterone in animals and brassinosteroids in plants. Steroids are known for their role in sexual development, but also have other functions such as maintaining the balance of electrolytes and water in the body.

Amino acid derivatives are hormones that are derived from amino acids, such as epinephrine and norepinephrine which are catecholamines and act as neurotransmitters and hormones. They are involved in the regulation of the “fight or flight” response.

Protein or peptides are hormones that are made of chains of amino acids and include insulin, which regulates blood sugar levels, and CLE peptides in plants, which play a role in the regulation of cell differentiation.

Gasses such as ethylene and nitric oxide are also considered hormones. Ethylene is a hormone that plays a role in plant growth and development, and Nitric oxide (NO) is a signaling molecule that acts as a neurotransmitter and hormone and is involved in various physiological processes such as blood flow, immunity and brain function.

Fields in Endocrinology:

Endocrinology is a broad field that encompasses several sub-fields. Some examples include:

1. Neuroendocrinology: The study of the interaction between the nervous system and the endocrine system.
2. Reproductive endocrinology: The study of hormones and their role in reproduction, including fertility, pregnancy, and menopause.
3. Pediatric endocrinology: The study of hormonal disorders in children and adolescents.
4. Geriatric endocrinology: The study of hormonal changes and disorders in the elderly population.
5. Metabolic endocrinology: The study of hormones and their role in metabolism, including diabetes and obesity.
6. Thyroid endocrinology: The study of the thyroid gland and its hormones, including thyroid disorders such as hypothyroidism and hyperthyroidism.
7. Adrenal endocrinology: The study of the adrenal glands and their hormones, including cortisol and aldosterone.
8. Bone and Mineral metabolism endocrinology: The study of hormones and their role in bone and mineral metabolism, including osteoporosis and metabolic bone disorders.
9. Cancer endocrinology: the study of the relation between hormones and cancer, including endocrine therapy of cancer.

Endocrine Disorders:

Endocrine disorders, or imbalances in hormone levels, can cause a wide range of diseases and symptoms. Some common examples include:

1. Diabetes: A disorder in which the body does not produce or properly use insulin, a hormone that regulates blood sugar levels.
2. Thyroid disorders: Imbalances in thyroid hormone levels can cause conditions such as hypothyroidism (too little thyroid hormone) or hyperthyroidism (too much thyroid hormone).
3. Osteoporosis: A disorder characterized by weak and brittle bones, often caused by imbalances in hormones such as estrogen and testosterone.
4. Cushing’s disease: A disorder caused by excessive production of the hormone cortisol by the adrenal glands.
5. Addison’s disease: A disorder caused by insufficient production of the hormones cortisol and aldosterone by the adrenal glands.
6. Polycystic ovary syndrome (PCOS): A disorder characterized by an imbalance in female sex hormones, often causing irregular menstrual periods and cysts on the ovaries.
7. Growth disorders: Imbalances in growth hormones can cause conditions such as gigantism (too much growth hormone) or dwarfism (too little growth hormone)
8. Acromegaly: A disorder caused by excessive production of growth hormone in adults.
9. Hyperprolactinemia: A disorder caused by excessive production of the hormone prolactin, which can cause infertility and breast milk production in women.

These are just a few examples of the many different diseases and symptoms that can be caused by endocrine disorders. These disorders can be caused by multiple factors and not only by hormonal imbalances.

Diabetes is one of the most common hormone disorders. Specifically, type 2 diabetes is the most common form of diabetes. It is a metabolic disorder characterized by high blood sugar levels caused by a combination of insulin resistance and inadequate insulin production. This can occur due to various factors such as obesity, lack of physical activity, genetics and unhealthy diet.

Type 2 diabetes is a chronic condition that affects millions of people worldwide, and it is becoming more prevalent due to the increasing incidence of obesity and sedentary lifestyle. It can lead to serious health complications such as cardiovascular disease, nerve damage, kidney damage, blindness, and amputations.

There are other common endocrine disorders such as thyroid disorders, osteoporosis, and polycystic ovary syndrome (PCOS) which affects a large number of people.

Treatments:

The treatment for endocrine disorders varies depending on the specific condition and its severity. Some common treatments include:

1. Medications: Hormone replacement therapy, insulin therapy, and oral medications such as metformin for diabetes and levothyroxine for thyroid disorders, are commonly used to regulate hormone levels and manage symptoms.
2. Surgery: Some endocrine disorders, such as thyroid cancer or tumors on the pituitary gland can be treated surgically.
3. Lifestyle changes: Making changes to diet and exercise habits can help to improve symptoms and manage some endocrine disorders such as diabetes and obesity.
4. Monitoring and follow-up: Regular monitoring and follow-up appointments with a healthcare provider are important for managing endocrine disorders, as hormone levels and symptoms can change over time.
5. Nutritional supplements: Some endocrine disorder such as osteoporosis, can be treated with nutritional supplements such as vitamin D and calcium.

It’s important to consult with a healthcare professional to determine the best course of treatment for a specific endocrine disorder, as some treatments may have side effects and may not be suitable for everyone. In addition, it’s important to be aware that the treatment of endocrine disorders is not only limited to medication, but also includes lifestyle changes, psychological support and education.

Discoveries:

Here are the landmark discoveries in endocrinology since 2000, expanded and separated into separate paragraphs:

1. Discovery of new hormones and hormone-like substances: One such discovery is irisin, a hormone produced by muscle cells that plays a role in regulating metabolism. Another is kisspeptin, a hormone that is involved in the regulation of the menstrual cycle and fertility.
2. Discovery of new hormone receptors: The GPR56 receptor for the hormone relaxin was identified and expands our understanding of the mechanisms by which hormones exert their effects.
3. Identification of genetic mutations causing endocrine disorders: This includes disorders like congenital adrenal hyperplasia and thyroid cancer. This has led to new diagnostic and treatment options for these disorders.
4. Advances in imaging techniques: Imaging techniques such as positron emission tomography (PET) and magnetic resonance imaging (MRI) have improved our ability to diagnose and monitor endocrine disorders. These techniques can provide detailed images of the body’s internal structures, allowing for more accurate diagnosis and monitoring of disorders.
5. Study of the gut-brain axis: The gut-brain axis refers to the complex communication network between the gut and the brain that is responsible for regulating various physiological processes. Many hormones are being discovered to have a role in this communication. Advances in this field have led to the development of new treatments for conditions such as obesity, diabetes, and mood disorders.

Books:

“Stress Hormones: Their Interaction and Regulation” by J. Axelrod and T.D. Reisine. It is a scientific book that focuses on the biology and physiology of stress hormones and their interactions and regulations in the body. It is published by the American Association for the Advancement of Science in 1984.

“General endocrinology”  Author(s) : Turner, C. D. Author Affiliation : Northwestern Univ., Evanston. Book : General endocrinology 1948 pp.xii + 604 pp.