Hormones (Types, Definition & Functions)

Endocrinology is the branch of medicine dedicated to hormones, hormone-secreting organs, and hormone effects. The study of hormones and their role is very important for health promotion as well as treating disease. 

Hormone imbalances can cause symptoms throughout the body, and understanding the role of endocrine organs and the major hormones can help the provider recognize when an imbalance may occur.

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What Are Hormones?

A hormone is a messaging chemical that specifically affects target organs and tissues. There are many circulating hormones in the body that perform multiple functions that help keep the body in a state of balance (homeostasis). 

Virtually every organ and tissue in the body is receptive to hormones that modulate their function. Hormones work in positive and negative feedback loops, which help maintain proper hormone levels. 

A positive feedback loop is similar to a fruit that continues to ripen as gasses are released. The more gasses released, the more the fruit ripens. 

A negative feedback loop is like a home thermostat. If the thermostat senses the temperature is too low, it releases more heat to reach a balance point. Hormones work in a similar way to keep the body in balance.

Which Body Tissues and Organs Make Hormones? 

Hypothalamus

The hypothalamus is an endocrine center in the brain that controls many aspects of hormone production. It helps connect the nervous and endocrine systems. The hypothalamus produces:

• Growth hormone-releasing hormone (GHRH)
• Corticotropin-releasing hormone (CRH)
• Thyrotropin-releasing hormone (TRH)
• Gonadotropin-releasing hormone (GnRH)
• Vasopressin 
• Dopamine
• Oxytocin
• Somatostatin

Pituitary Gland

The pituitary gland is connected to the hypothalamus. It serves as a storage organ for some hypothalamic hormones, including oxytocin and vasopressin. It also makes many important hormones, including:

• Prolactin
• Luteinising hormone (LH)
• Follicle-stimulating hormone (FSH)
• Growth hormone (GH)
• Thyroid-stimulating hormone (FSH)
• Adrenocorticotropic hormone (ACTH)

Thyroid

The thyroid is located in the anterior portion of the neck, and the hormones it makes impact many functions, specifically thermoregulation and metabolism. Thyroid stimulating hormone, made by the pituitary gland, acts on the thyroid to stimulate increased function. Hormones made by the thyroid are:

• Tri-iodothyronine (T3)
• Thyroxine (T4)
• Calcitonin

Parathyroid Glands

The parathyroid glands are also located in the neck; this gland regulates the mineral calcium, which has many functions, including acid-base balance and maintaining the musculoskeletal system. The primary hormone produced by this gland is:

• Parathyroid hormone (PTH)

Adrenal Glands

The adrenal glands help maintain the body’s sympathetic nervous system, blood pressure, and metabolism. The adrenal hormones include:

• Adrenaline
• Cortisol
• Aldosterone
• Testosterone
• Dehydroepiandrosterone (DHEA)

Pineal Gland

One of the smallest endocrine organs of the brain is the pineal gland, which regulates sleep and wake cycles. The hormone produced here is:

• Melatonin

Pancreas

The pancreas is one of the largest endocrine organs and is located in the abdominal cavity. It acts on blood sugar levels and the body’s energy storage. Hormones produced by the pancreas are:

• Insulin
• Glucagon
• Vasoactive intestinal peptide (VIP)
• Somatostatin

Ovaries

The ovaries are part of female anatomy and are located on either side of the uterus. The hormones produced here affect reproduction and the menstrual cycle. The ovarian hormones are:

• Estrogen
• Testosterone
• Progesterone
• Anti-mullerian hormone (AMH)
• Inhibin A and Inhibin B

Testes

The male endocrine hormones are the testes, which regulate male reproduction (sperm formation) and puberty. Hormones produced by the testes are:

• Testosterone
• Anti-mullerian hormone (AMH)
• Estradiol
• Inhibin A

What Conditions Do Hormonal Issues Cause?

The hormones created and secreted by endocrine organs require an exquisite balance of positive and negative feedback loops. Hormone imbalances can occur through internal and external factors, disrupting these feedback systems and affecting almost every body system. 

Conditions Caused by Hypothalamus Dysfunction

For example, the hypothalamus, which is the brain’s endocrine center, can become imbalanced and disrupt the sleep-wake cycle, blood pressure, heart rate, water and electrolyte balance, and temperature. (38) 

Conditions Caused by Pituitary Dysfunction

Next, hormonal imbalances in the pituitary gland can cause a variety of conditions. These may include diabetes insipidus (an imbalance of antidiuretic hormone), acromegaly (caused by a pituitary tumor), Cushing's syndrome (excess cortisol), and hypopituitarism (underactive pituitary). (29) 

Growth hormone deficiency and hyperprolactinemia may also occur when the pituitary gland is dysregulated.

Conditions Caused by Thyroid Dysfunction

More commonly known are disorders of the thyroid, which may include too little thyroid hormone (hypothyroidism) or excess thyroid hormone (hyperthyroidism). These can affect temperature regulation, energy levels, weight balance, menstruation, and mood.

Conditions Caused by Adrenal Gland Dysfunction

Next, an adrenal gland hormone imbalance can cause a cortisol imbalance and Addison’s disease (adrenal insufficiency). 

Conditions Caused by Pineal Gland Dysfunction

A pineal gland hormonal imbalance typically disrupts the sleep-wake cycle, since the pineal gland is responsible for excreting melatonin. 

Conditions Caused by Pancreas Dysfunction

Hormonal imbalances of the pancreas are also well-known and can cause severe conditions that require careful intervention. 

The major condition caused by an imbalance of pancreatic hormones is type 1 diabetes. This occurs when a patient’s immune system destroys the insulin-secreting cells of the pancreas, causing an insufficient release of insulin. 

In severe type 2 diabetes, the patient’s pancreatic cells stop producing insulin because of chronic blood sugar dysregulation. 

Conditions Caused by Ovarian Dysfunction

Many hormonal conditions experienced by women are rooted in ovarian dysfunction. An imbalance of female hormones can cause endometriosis, polycystic ovary syndrome, cancer, fibroids, infertility, and severe premenstrual syndrome.  

Conditions Caused by Testicular Dysfunction

Imbalances of male hormones can be related to testicular dysfunction. This can cause fertility issues, testicular cancer, and libido changes.

The Root Causes of Hormonal Imbalances 

Each endocrine organ has unique root causes leading to hormonal imbalances.

Root Causes of Hypothalamus Dysfunction

Because the hypothalamus contributes to many body systems, an imbalance of hormones from this gland can greatly influence homeostasis. Causes of hypothalamic hormonal imbalances include:

• Brain tumors can affect the ability of the hypothalamus to make and release hormones. 
• Nutritional deficiencies (e.g., anorexia nervosa) can downregulate the hypothalamus and reduce its ability to produce hormones. 
• Genetic conditions can play a role in hypothalamus function. 
• Neurological disease (e.g., multiple sclerosis) can cause damage to the nerves and brain, causing hormonal imbalances. 
• Radiation, chemotherapy, brain injury, and brain surgery can damage the hypothalamus and its hormone-regulating abilities. 

Root Causes of Pituitary Dysfunction

The pituitary gland, sometimes known as “the master gland,” also heavily impacts many hormonal functions, including cortisol, the balance of water absorption, growth, and lactation. The primary cause of pituitary dysfunction is:

• Tumors of the pituitary can cause excess growth hormones, prolactin, ACTH, ADH, and an imbalance of prolactin.

Root Causes of Thyroid Dysfunction

Hormonal imbalances of the thyroid are common among males and females. Causes of thyroid conditions may include:

• Autoimmune conditions can cause hyperthyroidism and hypothyroidism. 
• Inflammation may contribute to an overactive and underactive thyroid.
• Nodules of the thyroid often cause hyperthyroidism.
• Diet can affect the thyroid; specifically, a lack of iodine can cause hypothyroidism.
• Pituitary insufficiency can decrease thyroid-stimulating hormone.

Root Causes of Parathyroid Dysfunction

The hormones of the parathyroid gland can become imbalanced due to:

• Primary hyperparathyroidism is caused by a growth on the parathyroid gland, these are usually benign. 
• Hypoparathyroidism is an uncommon type of hormonal imbalance and usually occurs after the parathyroid gland is damaged during a surgical procedure. 

Root Causes of Adrenal Dysfunction

Hormonal imbalances of the adrenal glands can cause symptoms throughout the body and affect the stress response. Possible causes of adrenal hormonal imbalances are:

• Long-term corticosteroid use can cause Cushing syndrome.
• Tumors of the adrenal gland can cause excess cortisol. 
• Addison’s disease occurs when the adrenal glands are not making enough hormones to meet the needs of the body (primary adrenal insufficiency). 
• Congenital diseases such as congenital adrenal hyperplasia can cause adrenal hormone imbalances. 

Root Causes of Pineal Dysfunction

If the pineal gland hormone becomes disrupted, melatonin can become imbalanced, disrupting the sleep-wake cycle. Causes of pineal gland disruption include:

• Cysts and tumors of the pineal gland can interrupt melatonin production and release.

Root Causes of Pancreas Dysfunction

Hormonal imbalances of the pancreas are common and can cause many symptoms, including dysregulated blood sugar. Possible causes of pancreatic conditions include:

• Inflammation caused by excessive alcohol intake and gallbladder disease can cause pancreatitis. 
• Autoimmune conditions like type one diabetes cause the destruction of the pancreatic cells that produce insulin.
• Genetic disorders such as cystic fibrosis disrupt the release of pancreatic enzymes. 
• Cancer of the pancreas is an aggressive form of cancer that can cause rapid degradation of the organ’s function. 

Root Causes of Ovarian Dysfunciton

Proper ovarian function is vital for keeping the reproductive hormones balanced. Changes in ovarian hormone function can be caused by several factors:

• Endometriosis is a condition in which endometrial tissue grows outside of the uterus that can cause an imbalance in female hormones.  
• Polycystic ovary syndrome is a disease caused by genetic, environmental, and lifestyle factors that can disrupt ovarian function.
• Fibroids are benign growths of the uterine muscle that can cause hormone imbalances in women.  
• Cancer of the ovaries can affect women in many ways, including disrupting hormonal balance. 
• Obesity can change the levels of testosterone and estrogen in women. 

Root Causes of Testicular Dysfunction

The testes guide the production and maintenance of male reproductive hormones. Disruption of testosterone and other male hormones may be caused by:

• Medications such as pain medicine and corticosteroids can disrupt testosterone. 
• Obesity in men can result in low androgen levels. 
• Vitamin D deficiency can cause hypogonadism (decreased function of the testes). 
• Lifestyle choices like increased alcohol intake and smoking can change the levels of male hormones in the body. 

What Kind of Doctors Treat Hormone-Related Issues? 

Endocrinology is the study of hormones and their effect on the systems of the body. Endocrinologists are specialized physicians who diagnose and treat disorders of the endocrine glands and the hormones they produce. 

This field has sub-specialists who treat particular diseases, including thyroid conditions, diabetes, cancer, reproductive medicine, and pediatric hormone health. 

Integrative endocrinologists use the concepts of evidence-based medicine to seek out the root cause of hormonal imbalances and create personalized treatment plans. This specialty can utilize specialized lab testing to measure hormone levels and detect underlying causes of endocrine disease. Endocrinology providers can also provide testing to detect exposure to endocrine-disrupting chemicals. 

FAQ on Hormones 

#1. What are the most common issues caused by hormone imbalances? 

Hormone disorders can cause a variety of symptoms and greatly impact a patient’s quality of life. The most common hormone-related condition in the United States is type 2 diabetes, when the body is resistant to insulin, and the pancreas cannot create enough insulin to control blood sugar. 

Additionally, many people suffer from low or high thyroid hormone levels, which can affect their energy, weight, menstrual periods, and heart rate. 

Hormonal imbalances in women specifically can cause infertility and irregular periods. This can be due to PCOS and an imbalance of androgens. 

Low testosterone levels can also affect male fertility and the function of the testes. 

Additionally, acne can be a sign of a hormonal imbalance, specifically in puberty. Hormone fluctuations can affect the amount of sebum (oil) produced by the skin, which may contribute to clogged pores and acne. 

Excess weight gain can also indicate a hormone imbalance, which can be caused by many factors, including low levels of thyroid hormones (hypothyroidism) and excess cortisol. 

#2. What are hormones made of? 

Hormones are messaging chemicals made and released by endocrine organs  (e.g., the thyroid) and affect the function of tissues and organs. The majority of hormones in the body are made up of proteins. These proteins reach the target organs via the bloodstream and fit into a receptor site. 

The adrenal and reproductive hormones are steroid hormones, a specific class of chemical messengers. Hormones act similar to a lock and key; every hormone is a perfectly shaped molecule (“key)  for its target organ (“lock”). 

#3. How many hormones are in the human body? 

There are over 50 different types of hormones in the human body, each with its own specific function. 

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Key Takeaways 

• Many hormones and endocrine glands exist throughout the body, and these chemical messengers are maintained in a delicate balance.
• Knowledge about the body’s endocrine organs and the hormones they produce can help patients and providers identify hormonal imbalances. 
• Many symptoms throughout the body may be caused by a hormonal imbalance; testing and a root cause approach to medicine can help diagnose and treat many conditions. 
• Because hormones affect every body system, balanced hormonal health can promote overall well-being.