F.ENDOCRINOLOGY

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= **THE ENDOCRINE SYSTEM **   = __OVERVIEW __ This chapter on endocrine glands teaches about the different glands in the body, what and how hormones are produced, and the actions of the hormones they secrete. The endocrine glands include, but are not limited to the glands shown in the figure below. Other structures that can be considered endocrine glands are adipose tissue, the heart, kidneys, liver, skin, stomach and thymus.  Hormones are biologically active molecules that are secreted by the endocrine glands into the blood and carried to target cells that contain a specific receptor protein. Hormones help regulate total body metabolism, growth and reproduction. They are derived from a less active precursor molecule; polypeptide hormones are cut from a loncer chained prohormone and insulin is produced from proinsulin. There are different classifications of hormones: **Amines** which are derived from the amino acids tyrosine and tryptophan and are secreted by the adrenal medulla, thyroid, and pineal glands. **Polypeptides and proteins** which include antidiuretic hormone, growth hormone and insulin. **Glycoproteins** which consist of one protein bound to one or more carbohydrate groups and include follicle-stimulating hormone and luteinizing hormone. **Steroids** which are lipids that are derived from cholesterol and include testosterone, estradiol, progesterone and cortisol. Hormones also can work together to produce a certain effect, this is said to be synergistic. When one hormone enhances the effect of another hormone it is called a permissive effect, and when two hormones have opposite effects from one another they are said to have antagonistic effects. Nonpolar (lipophilic) hormones can pass through the plasma membrane to bind with receptor proteins within their target cells. These receptor proteins are located within the cytoplasm and nucleus. These receptor proteins are nuclear hormone receptors and function as transcription factors. Newly formed mRNA produced by activated genes within the cell direct the synthesis of specific proteins that change the metabolism of the target cell. ﻿   Some hormones cannot pass through the plasma membrane. they must bind to a receptor protein on the outer surface of the target cell. In this case, they are considered messengers from the endocrine gland. By the hormone binding to the receptor it activates intracellular mediators of the hormone action called second messengers. The second messengers exert the hormone's effects. The anterior pituitary and the posterior pituitary comprise the pituitary gland. The anterior pituitary is regulated by the hypothalamus along with feedback from the target gland hormones, where the posterior pituitary only stores and releases hormones produced in the hypothalamus. <span style="font-family: 'Times New Roman',Times,serif;">The adrenal glands are comprised of the adrenal cortex and the adrenal medulla which are structurally and functionally different. The adrenal medulla secretes hormones that effect the sympathetic nervous system, where the adrenal cortex secretes hormones that help regulate mineral and energy balance. <span style="font-family: 'Times New Roman',Times,serif;">The thyroid gland secrete hormones which are needed for growth and development and are responsible for determining the basal metabolic rate. The parathyroid gland releases hormones which help raise blood calcium levels. <span style="font-family: 'Times New Roman',Times,serif;">The pancreas releases hormones that control the blood glucose levels. <span style="font-family: 'Times New Roman',Times,serif;">The pineal gland releases hormones which keep the body regulated on a day/night cycle called circadian rhythms. <span style="font-family: 'Times New Roman',Times,serif;">Many other organs secrete hormones that help regulate digestion, metabolism, growth, immune function and reproduction. __<span style="color: #5e1c5e; font-family: 'Arial Black',Gadget,sans-serif;">ESSENTIAL QUESTIONS __ <span style="color: #5a1b5a; font-family: 'Arial Black',Gadget,sans-serif;">Describe how the hypothalamus regulates the action of the posterior pituitary and the anterior pituitary. <span style="font-family: 'Times New Roman','serif';">The hypothalamus regulates the secretion of two hormones which are stored in the posterior pituitary gland. Antidiuetic hormone and oxytocin are produced in the hypothalamus. They are moved along axons to the posterior pituitary for storage and use later. Neural endocrine reflexes from the hypothalamus controls the release of the hormones from the posterior pituitary. <span style="font-family: 'Times New Roman',Times,serif;">The anterior pituitary is regulated by hormonal control rather than neural control. The hypothalamus sends releasing and inhibiting hormones to the anterior pituitary. These hormones stimulate certain other hormones produced in the anterior pituitary to be released. The hormones in the anterior pituitary ( as well as the hypothalamus) hormones are controlled by the target organs it regulates, this is called negative feedback inhibition. The the release of hormones from the anterior pituitary are inhibited if there is an increased concentration of the hormones from the target organs. <span style="color: #5a1b5a; font-family: 'Arial Black',Gadget,sans-serif;">Describe one hormone that the posterior pituitary and anterior pituitary makes and describe the action of the hormone. <span style="font-family: 'Times New Roman',Times,serif;">An example of a hormone released by the posterior pituitary would be oxytocin. The release of oxytocin is seen in nursing mothers. Suckling from the baby sends nerve impulses to the hypothalamus which in turn stimulates the posterior pituitary to release oxytocin. The oxytocin stimulates the mammary glands to contract resulting in milk ejaculation. <span style="font-family: 'Times New Roman',Times,serif;">An example of a hormone that is released by the anterior pituitary would be follicle-stimulating hormone. This hormone is released to stimulate the ovaries to release sex hormones. It also releases luitenizing hormone to the ovaries which results in ovulation. <span style="color: #5a1b5a; font-family: 'Arial Black',Gadget,sans-serif;">What are trophic hormones and their role in hormone communication. <span style="font-family: 'Times New Roman',Times,serif;">Trophic hormones are the hormones which are released from the anterior pituitary. High concentrations of these hormones make the target organs to hypertrophy and low concentrations make them to atrophy. These hormones cause their target glands to secrete the hormones that are produced in that gland. An example of a trophic hormone is growth hormone (GH, somatotropin). GH stimulates the movement of amino acids to make proteins which promotes tissue growth. <span style="font-family: 'Times New Roman','serif';">

__<span style="color: #5e1c5e; font-family: 'Arial Black',Gadget,sans-serif;">SUMMARY __ <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Mechanisms of Hormone Action <span style="font-family: 'Times New Roman',Times,serif;">The way that hormones act on target cells depends on the chemical nature of the hormones. If the hormone can easily pass through the plasma membrane, it will bind with receptor proteins within the target cell. If the hormone cannot easily pass through, it will bind with receptors on the plasma membrane. Steroid and thyroid hormones bind to nuclear receptor proteins within the target cell. They are transported by plasma carrier proteins to the target cell. The hormone will then dissociate from the carrier to pass through the plasma membrane where it is then able to join with a receptor protein. The receptor, carrying the hormone then relocates to the nucleus to bind with DNA. This binding stimulates genetic transcription that results in new mRNA synthesis. The mRNA then codes for protein production which produces the hormonal effects on the target cell. <span style="font-family: 'Times New Roman',Times,serif;">Epinephrine and norepinephrine are examples of hormones that cannot easily enter through the plasma membrane. These hormones need Cyclic AMP as their second messenger to exert their hormonal effects on a target cell. The hormone binds to it's receptor on the plasma membrane. This interaction causes dissociation of G-proteins. A subunit of the G-protein moves until it finds the enzyme adenylate cyclase. The subunit and enzyme bind which catalyzes the breakdown of ATP. <span style="font-family: 'Times New Roman',Times,serif;">ATP → cAMP + PPi <span style="font-family: 'Times New Roman',Times,serif;">cAMP then activates and binds with to the inhibitory subunit of the enzyme protein kinase, which causes dissociation and activation of the catalytic subunit of the enzyme. This causes an increase in protein kinase enzyme activity. The active protein kinase catalyzes the phosphorylation of different proteins in the target cell. cAMP acting through protein kinase mediates the activity of enzymes in the target cell altering the metabolism of the target tissue. <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Is it Hyperthyroidism or Hypothyroidism? <span style="font-family: 'Times New Roman',Times,serif;">Inadequate secretion of thyroid hormones is called hypothyroidism. Individuals that are hypothyroid have abnormally low basal metabolic rates, experience weight gain and lethargy and have a decreased ability to adapt to cold stress. In adults, this disorder can cause myxedema which results in the accumulation of mucoproteins and fluid in subcutaneous connective tissues. Symptoms noted with this disorder are swelling of the hands, face, feet and tissues around the eyes. Hypothyroidism results from but is not limited to a thyroid gland defect. It can also result from inefficiencies of thyrotropin-releasing hormone secretion from the hypothalamus, thyroid secreting hormone from the anterior pituitary or iodine in the diet. A lack of iodine in the diet causes an elevation in TSH secretion which stimulates excessive growth of the thyroid. This disease is iodine-deficiency (endemic) goiter. Iodine supplements can reverse hypothyroidism and goiter caused by iodine deficiency. <span style="font-family: 'Times New Roman',Times,serif;">Opposite of hypothyroidism is hyperthyroidism, which is caused by excessive thyroid hormones. This condition causes high basal metabolic rates, weight loss, nervousness, irritability, intolerance to heat, and an increase in output and blood pressure. Graves' disease can also cause a goiter. Autoantibodies exert TSH-like effects on the thyroid. The production of these antibodies is not stopped by negative feedback. The high secretion of thyroxine cannot turn off the excessive stimulation of the thyroid and a goiter is developed. This condition is also called thyrotoxicosis and is accompanied by exophthalmos due to swelling in the orbits.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Autocrine and Paracrine Regulation <span style="font-family: 'Times New Roman',Times,serif;">Molecules that are produced in an organ and are active within that organ are considered to be autocrine and paracrine regulators. Autocrine regulators act on the sme cell type that produced them where paracrine regulators act on a different type of tissue than the one that produced them. Prostoglandins are a diverse group of autocrine regulators. They are produced in almost every organ and have many regulatory functions. In the immune system prostoglandins promote the inflammatory process. In the digestive system these autocrine regulators inhibit gastric secretions and influence intestinal motility and fluid absorption. Some prostoglandins act as vasoconstrictors while others act as vasodilator in the circulatory, respiratory and urinary systems. An Inhibitor of prostoglandin synthesis is aspirin which is a nonsteroidal anti-inflammatory drug (NSAID). Cyclooxygenase enzyme needed for prostoglandin synthesis inhibited by the effects of these types of drugs. __<span style="color: #5e1c5e; font-family: 'Arial Black',Gadget,sans-serif;">APPLICATION __

<span style="font-family: 'Times New Roman',Times,serif;">Given to treat inflammatory conditions glucocorticoids such as hydrocorisone, prenisolone and dexamthasone can suppress the immune system while suppressing inflammation. This can mask the signs of infections such as urinary tract infections. The usual symptoms will not be seen and the steroids will mask the inflammation of the infection. This is something a nurse should be aware of. Infections can be very deadly for the elderly. They can present quickly and intervention given as soon as possible. I have a resident that I take care of at work, he fell awhile ago and broke his ankle and had surgery. At the same time he is on prednisone. After having the boot on his foot and leg he now has skin issues that we are having trouble with getting healed up. I think this can be an issue with steroid use also. The immune system is suppressed so the body cannot fight the infection properly. Part of the endocrinology system that is important to understand as a nurse is ADH hormone. The ADH hormone if not working properly can affect the levels of edema throughout the body and could be one of the first signs of a more serious heart condition. Also the ADH if not properly regulated by the body can have serious effects on the blood pressure. As a nurse to do proper assessments could be the first clue for the doctor to diagnose more significant health problems.

As a nurse I will be doing assessments of the patients and I am expected to be able to notice the signs and symptoms of hyperthyroidism and hypothroidism (shown in table 11.8 above) and be able to effectively notice that there are abnormalities and be able to report back to the MD with the correct and appropriate information. __<span style="color: #5e1c5e; font-family: 'Arial Black',Gadget,sans-serif;">CASE STUDY __ __<span style="color: #5e1c5e; font-family: 'Arial Black',Gadget,sans-serif;">[|Andrea: The Death of a Diabetic] __
 * 1) What are the symptoms of diabetes?

Symptoms of diabetes mellitus are polyuria, polydipsia, weight loss, polyphagia, hyperglycemia and glycosuria. Complications can occur in the eyes, kidney, nervous system, skin and circulatory system. Infections are common and atherosclerosis can develop as well as ketoacidosis being a constant danger.


 * 1) What are the different types of diabetes?

There is type 1 diabetes which is considered insulin-dependent diabetes. This type has previously been referred to as juvenile-onset diabetes. This type is controlled with insulin injections. This type comprises of about 5-10% of the population of people with diabetes. The other main type is type 2 diabetes which is considered non-insulin dependent diabetes, which has been previously referred to as adult-onset diabetes. This type can be controlled by diet and exercise. Another type is called gestational diabetes mellitus, which occurs when pregnant women develop an intolerance to glucose. Glucose levels usually return to normal after pregnancy.


 * 1) What is known about the genetics of diabetic disorders?

Some people may have a genetic predisposition to developing diabetes. The pathologic sequence leading to the autoimmune destruction of beta cells involves genetic and environmental factors along with immune regulation and chemical mediators. [] “The Genetics of Diabetes Mellitus”


 * 1) What goes wrong when juvenile diabetes sets in?

Type 1 diabetes is caused by the destruction of beta cells which produce insulin in the islets of Langerhans of the pancreas. It may be an autoimmune response of the pancreas attacking itself after a viral infection or administration of certain drugs.


 * 1) What is known about the role that insulin plays in the processing of blood sugar?

Insulin as a hormone or injection controls the levels of glucose in the blood. Insulin is used by the body to regulate glucose intake into body cells from the bloodstream. When there is no insulin produced (type 1), insufficient amounts or the cells are resistant to the insulin (type 2) glucose is not taken into the cells and hyperglycemia occurs.

Close monitoring of the blood glucose levels is needed. Blood sugars can be checked up to four times a day. Type 1 is controlled mainly by insulin. Depending on how much control of the blood glucose levels are needed, an individual can have one to several doses of insulin per day as well as a sliding scale for extra insulin when needed. Low carbohydrate meal planning and exercise are added for extra control. Type 2 is more controlled with diet and exercises. The individual can also take one or more oral agents such as glimipiride as well as insulin if needed. Mosby’s Medical Dictionary, 8th Edition, Pg. 542 Understanding Medical Surgical Nursing, Williams and Hopper, 3rd Edition, Pg. 853                               Sources: <span style="font-family: 'Times New Roman','serif';">Fox, Stuart Ira. (2009). //Human Physiology//. New York, NY: McGraw-Hill. Comerford, Karen and Donofrio, Jo. (2006). //Pathophysiology Made Incredibly Easy//. New York, NY:Lippincott Williams & Wilkins. <span style="font-family: 'Times New Roman','serif';">Home G.HEMATOLOGY
 * 1) What are the various treatments for the different diabetic conditions?