The Amazing Endocrine System
The endocrine system is an amazing part of the body. It is amazing in that all of its parts work together to keep the body functioning as it should and to influence the processes that should take place to make human beings healthy such as growth, ovulation, pregnancy, sperm generation, sugar, salt and calcium metabolism and many other processes that occur. While its complexity cannot be fully explained in a short space, some of its amazing features can be discussed along with some of the possible disorders that may occur in the endocrine system.
Hypothalamus
The hypothalamus is actually a part of the brain rather than a separate gland like the pituitary gland, which is located near the hypothalamus, and which works in conjunction with the hypothalamus. Kara Rogers, author of The Endocrine System explains that the hypothalamus is cone-shaped and projects down from the brain with the funnel-shaped stalk connecting to the pituitary gland. It also acts as a control center for the autonomic nervous system including its effects on the nervous system because of its interaction with the pituitary gland (Rogers, 2012, p. 158). That connection to the pituitary gland is both nerves and chemical whereas the other glands in the endocrine system have only a chemical connection to the pituitary gland and other parts of the body. The hypothalamus secretes hormones, but also neurotransmitters, so that it connects the stimuli from the endocrine system with the brain by way of its connection to the pituitary gland that regulates many parts of the body. Morley (2019) of Merck Manuals (2019) says, “The hypothalamus receives input from virtually all other areas of the central nervous system and uses it to provide input to the pituitary. In response, the pituitary releases various hormones that stimulate certain endocrine glands throughout the body. Changes in circulating levels of hormones produced by these endocrine glands are detected by the hypothalamus, which then increases or decreases its stimulation of the pituitary to maintain homeostasis” (Morley, 2019). Other parts of the body will inform the hypothalamus of the need for hormones or the need to regulate the hormones, and the thalamus then signals the pituitary gland to either send signals, send hormones or stop sending hormones.
Another connection that the pituitary gland and the hypothalamus have is the hormones that they secrete. Whatever the hormone the pituitary gland secretes, the hypothalamus secretes a regulatory one. For instance, the hypothalamus secretes thyrotropin-releasing hormone (TRH) which tells the pituitary gland to release thyroid-stimulating hormone (TSH) which regulates the function of the thyroid gland. The hypothalamus has the connection to the brain which controls the entire body and informs the hypothalamus that more thyrotropin is necessary. Thyroid-stimulating hormone (TSH), also known as thyrotropin, has many functions: it stimulates the synthesis and secretion of thyrotropin by the anterior pituitary gland. That stimulates the thyroid to release thyroxin, which is one of the essential hormones for life in the human body (Rogers, 2012, p. 130). Corticotropin-releasing hormone (CRH) corresponds to Adrenocorticotropic hormone (ACTH, corticotropin), which regulates the release of cortisol from the adrenal glands. Gonadotropin-releasing hormone (GnRH), Growth hormone–releasing hormone (GHRH) and Growth hormone–inhibiting hormone (somatostatin GHIH) secreted by the hypothalamus correspond to and regulates Growth hormone (GH) secreted by the anterior pituitary gland which stimulates growth, cell reproduction and regeneration. Prolactin-inhibiting hormone (PIH) secreted by the hypothalamus corresponds with Prolactin (PRL) secreted by the anterior pituitary gland which stimulates milk production during the last stage of pregnancy. Also related to PH and PRL and Luteinizing hormone (LH), also known as Leydig cell–stimulating hormone (LCSH) and Follicle-stimulating hormone (FSH) which tell the ovaries to release eggs and optimistically prepare the uterus for egg implantation. Finally, Melanocyte-inhibiting hormone (MIH) secreted by the hypothalamus corresponds with Melanocyte-stimulating hormone (MSH) secreted by the anterior pituitary gland. MIH regulates MSH, which stimulates melatonin production. Melatonin is responsible for the pigmentation in skin.
Diseases and Disorders of the Hypothalamus
Some disorders of the hypothalamus include tumors, encephalitis, and other inflammatory lesions. Tumors are diagnosed with brain imaging and treated with surgery and/or radiation or chemotherapy. Encephalitis and other inflammatory lesions are diagnosed with imaging, spinal tap, blood or urine samples, EEG, or biopsy. Encephalitis is treated based on its severity. Mild encephalitis would be treated with bed rest, plenty of fluids and anti-inflammatory medication such as naproxen sodium. It may be viral in nature so then it would be treated with anti-viral medications such as Acyclovir (Zovirax), Ganciclovir (Cytovene) or Foscarnet (Foscavir) (Endocrine Web, 2019). Many of the diseases or disorders that can be attributed to the hypothalamus are often discussed as diseases or disorders of the pituitary gland.
Anterior Pituitary
One of the hormones that the anterior portion of the anterior pituitary gland secretes is ACTH. The action of ACTH is limited in humans to the areas of the adrenal cortex where cortisol and corticosterone are formed. ACTH’s release is regulated by CRH release by the hypothalamus in response to impulses transmitted by the nervous system in response to stress (Rogers, 2012, p. 94). The anterior pituitary also releases TSH which stimulates the thyroid gland into action as discussed above. LH and FSH control the production of sex hormones. The release of these hormones are stimulated by GnRH and suppressed by estrogen and testosterone. In women, LH and FSH stimulate the ovary to create follicles and to ovulate. In men, FSH stimulates sperm production. LH acts on the Leydig cells, in the testes to secrete testosterone. GH stimulates body growth and regulates metabolism. Prolactin is produced during pregnancy. The major function of prolactin is stimulating milk production. Also, prolactin release occurs during sexual activity and stress (Endocrine Web, 2019). Disorders or diseases that affect the anterior pituitary gland often involve the hypothalamus too.
Posterior Pituitary
The posterior pituitary secretes Vasopressin (antidiuretic hormone [ADH]) and Oxytocin. Vasopressin plays an important role in maintaining the concentration of salt and glucose in the blood. That means that it also helps to maintain the adequate water levels in extracellular fluid (Rogers, 2012, p. 131). The hypothalamus detects water, salt and glucose levels and sends a signal to the posterior pituitary to release vasopressin. The hypothalamus gets signals near the end of pregnancy that delivery will be soon. That then signals the posterior pituitary to release Oxytocin, which stimulates contractions in the uterus during labor, controls bleeding following delivery, and stimulates milk production. Oxytocin is also involved in orgasms and other pleasurable activities (Endocrine Web, 2019). When the pituitary or hypothalamus are not in perfect working order, several disorders or diseases may arise.
Disorders and Diseases of the Pituitary Gland
Disorders and diseases of the pituitary gland include Cushing’s Disease, a rare disorder that affects 10 to 15 people per million per year. It is caused by an over active adrenal cortex, which may be due to a tumor on the pituitary gland. It is rare that this is the cause though. Women are more prone to Cushing’s Disease than men, and it may appear following pregnancy. Cushing’s Disease is diagnosed with blood and urine samples. It treated by first figuring out the cause. If it is a tumor causing it, the treatment is usually surgery. If it is excessive hormone production, medication is given to block excessive production of cortisol in the adrenal gland such as ketoconazole, mitotane (Lysodren) and metyrapone (Metopirone). Mifepristone (Korlym, Mifeprex) (Endocrine Web, 2019). Recurring Cushing Disease symptoms is often called Cushing Syndrome. That means that other glands may be affected by the disorder, which then could cause other diseases or disorders. Diamanti-Kandarakis, et al. (2019) of the European Journal of Endocrinology list the different methods that have been used to treat the disorder, which can also lead to further endocrine system disorders. “Several compounds, including ketoconazole, metyrapone, etomidate, and mitotane, have been commonly used in the therapeutic management of severe hypercortisolism for any etiology of endogenous Cushing’s syndrome or control of excess steroid production in adrenocortical carcinoma. . . They can cause subsequent decrease in cortisol secretion and adrenal insufficiencies” (Diamanti-Kandarakis, et al., 2019, p. 90). Unfortunately, the amazing design of the interactivity of the endocrine system also has some negative aspects too.
Tumors that affect pituitary gland functioning are diagnosed with blood tests and brain imaging. If the tumor produces ACTH, GH or TSH they are usually removed surgically or if that is not possible, radiation is used to try to limit their effectiveness or destroy them. Benign tumors are treated with dopaminergic agonists such as bromocriptine, pergolide, cabergoline), which lower blood levels and often shrink the tumor. Surgery and radiation therapy are usually unnecessary (Morley, 2019). The fact that other hormones are used to treat a glandular issue highlights another one of the amazing features of the endocrine system.
Thyroid
The thyroid gland is located at the front part of the lower neck below the larynx. It is butterfly shaped and has two parts to it. The hormones that are associated with the thyroid gland are produced in the thyroid using iodine. Iodine ingested in the diet is converted by the thyroid into the hormones Triiodothyronine (T3) and Thyroxine (T4), which are vital to metabolism and growth. T4 is the more abundant hormone. It stimulates the consumption of oxygen by cells and tissue, which is the vital function known as metabolism. T3 also helps in metabolism and digestion. If too much of these hormones are secreted, a condition called hyperthyroidism occurs. If too little is secreted, then hypothyroidism occurs. Calcitonin is another important thyroid hormone. It acts like the hypothalamus in that it opposes some of the actions of the parathyroid gland by regulating blood calcium and phosphate levels (Endocrine Web, 2019). The diseases and disorders of the thyroid gland can be mild and easy to treat or very serious and life-threatening.
Diseases and Disorders of the Thyroid Gland
Hyperthyroidism is diagnosed with a blood test. . It can be treated with antithyroid medications such as propylthiouracil (PTU) or methimazole. These two medications target T4 and T3 specifically. Another type of antithyroid medication are beta blockers such a propranolol or metoprolol, which works throughout the body (Endocrine Web, 2019). Radioactive iodine may also be prescribed and surgery may also be an option. Another similar but opposite disorder, hypothyroidism may be primary or secondary to other thyroid malfunctions. “Primary thyroid dysfunction is usually related to painless thyroiditis . . . due to the release of thyroid hormone as a result of thyroid gland inflammation, followed by a hypothyroid phase. . . . The patient may present with primary hypothyroidism (i.e. with an elevated TSH and low or normal free T4). The diagnosis of secondary (central) hypothyroidism is on other hand suspected when the free T4 level is low and TSH is low or low-normal” (Diamanti-Kandarakis, et al., 2019, pp. 79-80). Hypothyroidism is diagnosed with a blood test and also on family and patient history. Usually a physical exam reveals evidence of hypothyroidism too such as dry skin. The condition is treated with thyroid hormone replacement therapy.
Other thyroid disorders include thyroid cancer. Many people have nodules on their thyroid glands and most are benign. However, thyroid cancer is the most common endocrine system cancer. It occurs when those nodules become cancerous tumors It is the fastest growing cancer in the United States, in both men and women (Hormone Health Network, 2019). It is diagnosed through blood tests, imaging and biopsy. Thyroid cancer is highly treatable and is not usually fatal. The way it is treated is by removing the thyroid gland. If the cancer is contained within the gland, that should take care of it. Radioactive iodine may also be used to make sure the cancer is completely gone. If the cancer has advanced cancers, which occurs in less than 5% of patients, then it may require chemotherapy (Hormone Health Network, 2019). Thyroid hormone replacement therapy is necessary for the rest of the patient’s life.
Parathyroid
The parathyroid glands are located in the neck behind the thyroid gland. They are very small, about the size of a grain of rice. Most people have four parathyroid glands. Their main function is controlling the body’s calcium levels. Parathyroid hormone (PTH) acts on the bones, intestines and kidneys. It triggers the bones to release calcium stores to the blood when the supply is too low. In the intestines, PTH helps with vitamin D metabolism, which allows the body to absorb more of the calcium it digests from food. In the kidneys, PTH stops the release of calcium in the urine while increasing vitamin D production (Hormone Health Network, 2019). This gland like many others has a connection to the hypothalamus and the pituitary gland.
Diseases and Disorders of the Parathyroid Gland
Disorders of the parathyroid gland include hypercalcemia, which is caused by too much PTH. It is diagnosed by blood test and treated by lowering blood calcium levels through excretion and reduction of bone absorption of calcium. A diuretic may be prescribe and medications such as zoledronate to treat hypercalcemia (Morley, 2019). Too little PTH can cause hypoparathyroidism, which leads to low blood calcium levels. This is diagnosed with a blood test and treated with calcium supplements and vitamin D. Calcium supplements can include over the counter medications such as antacids that use calcium as their base.
Adrenal Cortex
The adrenal glands are located above the kidneys. They are made up of an outer cortex and an inner medulla. The adrenal cortex produces glucocorticoids, primarily cortisol and mineralocorticoids, primarily aldosterone. Glucocorticoids promote and inhibit gene transcription which result in anti-inflammatory actions and increased liver function. Mineralocorticoids regulate the exchange of sodium and potassium in the kidneys (Morley, 2019). The adrenal glands affect many processes of the body including promoting healthy heart function, stress response, the proper use of carbohydrates and fat, distributing stored fat, and promoting health gastrointestinal functions. They are also responsible for some things that people may wish they would not do like body odor and pubic hair (Hormone Health Network, 2019)
Adrenal Medulla
The inner part of the adrenal glands secrete epinephrine and norepinephrine, which mainly act on the sympathetic nervous system. These hormones are also known as adrenaline and noradrenaline and are responsible for the “fight or flight” mechanism in humans triggered by dangerous situations or extreme stress. Adrenaline and noradrenalin help to control blood pressure, heart rate, sweating, and other activities also regulated by the sympathetic nervous system (Morley, 2019). The connection to the brain for the adrenal glands is the hypothalamus.
Disorders and Diseases of the Adrenal Glands
Disorders of the adrenal gland include adrenal deficiency syndrome. If there is too little adrenaline being produced, the result is Addison’s Disease. This is diagnosed with blood tests but a CT scan or MRI may also be done to find the cause of the insufficiency. Stratakis (2019) of the National Institute of Health (NIH) explains that several conditions such as surgery, illness, pregnancy or serious injury could affect adrenaline production levels (Stratakis, 2019). If too much adrenaline is being produced, then the result it Cushing syndrome as discussed above.
Other disorders resulting from overproduction of adrenal hormones include hyperaldosteronism, adrenal virilism, and pheochromocytoma. Hyperaldosteronism is a disorder that occurs when there is too much aldosterone in the blood, which can lead to hypertension and low blood potassium levels. It is diagnosed with blood and urine samples and imaging. It is treated with surgery to remove tumors or with a selective aldosterone blocker such as spironolactone or amiloride (Morley, 2019). Adrenal virilism is a disorder that suppresses sex characteristics. The symptoms depend upon the patient’s sex and age at onset and are more noticeable in women than in men because it can cause women to grow hair on their face and stop menstruating and to have a dramatic and natural reduction in breast size. In men it can cause infertility and low sperm production. It is diagnosed with blood and urine tests and treated with oral glucocorticoids or surgery to remove tumors that may be causing it. Pheochromocytoma is a tumor that is diagnosed through blood and urine samples and imaging. It is treated by removing the tumor and/or radiation or chemotherapy.
Ovaries
The ovaries are the female gonads. They are located near the uterus and anchored to it by fibrous tissue. They produce eggs each month. When they release the egg into the Fallopian tubes, tissue forms over the place where the egg once was. That spot where the tissue forms is called the corpus luteum and it secretes progesterone which thickens the walls of the uterus for the implantation of a fertilized egg. The ovaries also produce estrogen. Estrogen is responsible for the development of female sex characteristics at puberty and the maintenance of healthy reproductive organs until menopause. When a woman is pregnant, more estrogen and progesterone is produced. Progesterone prevents uterine contractions and prepares the breasts for lactation. Estrogen increases at the end of pregnancy and alerts the pituitary gland to release oxytocin. Progesterone also helps to ready the body to give birth and lactate (Endocrine Web, 2019).
Disorders and Diseases of the Ovaries
If a woman has low levels of progesterone, she may suffer from several disorders including abnormal uterine bleeding, irregular or missed periods, spotting and abdominal pain during pregnancy and/or frequent miscarriages (Hormone Health Network, 2019). Ovarian cysts are fluid filled sacs that can occur in women of any age, but mostly during child-bearing years. Most are benign. They are diagnosed with imaging and/or laparoscopy and usually treated by waiting for them to diminish, a prescription for birth control pills, or surgery. Ovarian cancer is another disorder of the ovaries. It is difficult to detect until it has progressed into the later stages, which makes it one of the most deadliest cancers for women. It is diagnosed through blood tests and imaging. It is treated with surgery to remove one or both of the ovaries and possibly the uterus and connecting tissue too. Chemotherapy and radiation may also be done to prolong life.
Testes
The testes are the male gonads. They are located in the scrotum. There are two of them. Inside the testes are tubules that create sperm. Tissue between the tubules secretes testosterone, which initiates physical development in boys at puberty. It also maintains masculine characteristics throughout life. The hypothalamus and the pituitary gland control how much testosterone is produced and secreted.
Disorders and Diseases of the Testes
Disorders of the testes include hypogonadism, which is caused by too low levels of testosterone production. It is diagnosed both clinically with a blood test and treated with testosterone replacement therapy. Gynecomastia, which is breast enlargement in newborn baby boys, pubescent boys or in middle-aged men. The enlargement is due to a benign increase in breast tissue that is caused by an imbalance in estrogen and testosterone. Gynecomastia is common in newborn boys and caused by exposure to their mother’s estrogen. In pubescent boys, it is caused by the hormonal changes taking place in their bodies. In middle-aged men, it is caused by hormonal changes due to aging, increased body fat and medications. It is diagnosed clinically and through blood tests, and it is usually not treated as it usually goes away on its own (Hormone Health Network, 2019).
Testicular cancer is another disorder of the testes. It is also diagnosed with a blood test and treated with surgery and/or radiation. If it is diagnosed early enough, then it is usually curable. However, there are more aggressive types of testicular cancer that can be fatal.
Pancreas
The pancreas is an organ located next to the duodenum. It is both an exocrine gland and an endocrine gland, which means it secretes hormones directly into the blood but it also secretes hormones into ducts that are then taken to the place where they are used such as the stomach to aid in digestion of glucose. Its function is to maintain the body’s glucose balance. The main hormones of the pancreas are glucagon and insulin. Both function to regulate blood sugar levels. Glucagon regulates insulin by stimulating cells to release glucose when more blood glucose is needed or insulin has made the levels of blood glucose too low. Insulin works by allowing the cells to absorb and use glucose for energy. It lowers blood glucose levels. Somatostatin is another pancreatic hormone. It regulates both insulin and glucagon by lowering their levels in the blood. It also regulates sodium levels in the blood (Morley, 2019).
Disorders and Diseases of the Pancreas
The most widely known diseases of the pancreas are diabetes type 1 and diabetes type 2. Type 1 diabetes it is a malfunction in the amount of insulin that is produced. The body does not produce enough to handle the glucose levels in the body. It is diagnosed usually around puberty, but can be diagnosed at any age. It is diagnosed through blood tests, and it is treated with insulin replacement therapy. That is the only known therapy for diabetes. Type 1 diabetes is a lifelong illness, but it can be controlled with insulin and a diabetic can lead a normal life. However, it causes complications such as blindness, heart disease and other problems as a person with type 1 diabetes ages.
Type 2 diabetes is more common than type 1 and is usually diagnosed in mid-life. People with type 2 diabetes can produce insulin, but the body becomes resistant to the action of insulin, and does not use the insulin as it should. That means the insulin does not carry glucose to cells. The body usually still makes insulin, but not enough to do the work that it should (Hormone Health Network, 2019). Type 2 diabetes is diagnosed with blood tests and treated in a variety of ways. One way is lifestyle changes. Type 2 diabetes often occurs in people who are overweight, so losing weight can control it. Some people may also have to take insulin to control type 2 diabetes.
Hyperglycemia is a condition that is caused by over production of glucagon. It is diagnosed with blood tests and can be treated with an adjustment to diet and increased exercise. If the patient is taking insulin, the dose may need adjustment. Hypoglycemia is the opposite of hyperglycemia. It occurs when blood glucose levels are too low due to overproduction of insulin. It can also occur when a person who uses insulin takes too much. It is diagnosed with a blood test and treated by adjusting medications, dietary changes and other lifestyle changes.
Pancreatic cancer is the most serious of pancreatic disorders. It occurs when growths on or in the pancreas become malignant. It is often asymptomatic and since the pancreas is hidden among the other organs in the torso, it is hard to detect the lumps. By the time it is usually diagnosed, it is too late and the diagnosis is terminal. Pancreatic cancer is diagnosed with imaging and blood tests, but needle aspiration may also be done. It can be treated with chemotherapy, but the prognosis for pancreatic cancer is a very low survival rate in less than five years.
Conclusion
The endocrine system is amazing because it has so many parts that are spread throughout the body, yet, they all work together to keep the body in balance. With the hypothalamus relaying messages from the body to the pituitary gland, and the pituitary gland relaying messages to the rest of the endocrine system, the process is efficient. When there is a disorder in one of the parts of the endocrine system, it is often because another part of it is not doing the job it is supposed to do. Learning about how the endocrine system works will help me to be a better nurse.
References
Diamanti-Kandarakis, E., Duntas, L., Kanakis, G. A., Karavitaki, N., Kassi, E., & Nader, S. (. (2019). Diagnosis of Endocrine Disease: Drug-induced endocrinopathies and diabetes: a combo-endocrinology overview. European journal of endocrin. European Journal of Endocrinology, 181(2), 73-105. Retrieved from https://eje.bioscientifica.com...
Endocrine Web. (2019). The Endocrine System. Retrieved from Endocrine Web: https://www.endocrineweb.com/
Hormone Health Network. (2019). Hormone Health. Retrieved from Hormone Health Network: https://www.hormone.org
Morley, J. (2019, March). Overview of the Endocrine System. Retrieved from Merck Manual Professional Version: https://www.merckmanuals.com/p...
Rogers, K. (Ed.). (2012). Endocrine System. New York: Encyclopedia Britannica.
Stratakis, C. (2019). Adrenal Insufficiency & Addison’s Disease. Retrieved from National Institue of Health: https://www.niddk.nih.gov/heal...
