UNIT SUMMARY

This unit contained a lot of information, all related to endocrine glands. Some of the major topics included the different endocrine glands and hormones, mechanisms for hormone action, the pituitary gland, the adrenal glands, thyroid and parathyroid glands, pancreas and other endocrine glands, as well as autocrine and paracrine regulation.


THREE MAJOR CONCEPTS OF ENDOCRINOLOGY

Hormones can be chemically classified into four groups:


1. Amines. These are amino acid-derived hormones, and they include those secreted by the adrenal medulla, thyroid, and pineal glands.

2. Polypeptides and proteins. These hormones are chains of amino acids of less than or more than about 100 amino acids, respectively. So, a hormone with 4 amino acids (antidiuretic hormone) is too small to be called a protein, but a hormone with 191 amino acids (growth hormone) can be called a protein.

3. Glycoproteins. These particular molecules consist of a protein bound to one or more carbohydrate groups. Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are examples.

4. Steroids. Steroid hormones are lipids that are synthesized from cholesterol. They are characterized by four interlocking carbohydrate rings. These form the steroid hormones of the adrenal cortex and gonads.



Pituitary Hormones

 

The pituitary is a small, pea-sized gland located at the base of the brain that sends signals to the thyroid and adrenal glands and the ovaries and testes, directing them to produce thyroid hormone, cortisol, estrogen, testosterone, and other hormones. These hormones affect metabolism, blood pressure, sexuality, reproduction, and other vital body function. The pituitary gland also produces growth hormone and prolactin for milk production. The pituitary gland is divided into an anterior lobe and a posterior lobe.

The anterior pituitary hormones are as follows:

  • Growth hormone (GH, or somatotropin). A hormone that stimulates growth of the skeleton and soft tissues during the growing years and that influences the metabolism of protein, carbohydrate, and fat throughout life.
  • Thyroid-stimulating hormone (TSH, or thyrotropin). This hormone is promotes growth of the thyroid gland and stimulates it to produce more thyroid hormones.
  • Adrenocorticotropic hormone (ACTH or corticotropin). ACTH stimulates the adrenal gland to make glucocorticoids or steroids, which influence metabolism and act as anti-inflammatory and immunosuppressive agents. It is an essential pituitary hormone which causes the adrenal glands to release cortisol, the stress hormone.
  • Follicle-stimulating hormone (FSH, or folliculotropin). In females, FSH stimulates the development of the ovarian follicles. In males, it stimulates the production of sperm in the seminiferous tubules.
  • Luteinizing hormone (LH, or luteotropin). In females, LH stimulates ovulation and the development of a corpus luteum. In males, it stimulates the Leydig cells to secrete androgens.
  • Prolactin (PRL). This hormone stimulates lactation in postpartum females. It may also participate in regulating gonadal function in some mammals.
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The posterior pituitary releases two hormones:

  • Antidiuretic hormone (ADH, or arginine vasopressin (AVP)). ADH is produces by the hypothalamus and released from the posterior pituitary. It acts on the kidneys to promote water reabsorption, therefore decreasing the urine volume.
  • Oxytocin. This hormone is also produced by the hypothalamus and released from the posterior pituitary. It stimulates the contraction of uterine smooth muscles and promotes milk letdown in females.



Diseases of The Thyroid

Millions of Americans have some form of thyroid disease. Here are brief explanations of a few of the many types of thyroid disease.

Grave’s Disease: This is the most common cause of hyperthyroidism. It is a chronic disorder in which a person’s i
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mmune system produces antibodies that attack the thyroid, causing inflammation, damage, and the production of excessive amounts of thyroid hormone. Graves' disease is rarely life-threatening. Although it may develop at any age and in either men or women, Graves' disease is more common in women and usually begins after age 20. There's no way to stop your immune system from attacking your thyroid gland, but treatments for Graves' disease can ease symptoms and decrease the production of thyroxin. Some symptoms include anxiety, irritability, fatigue, rapid or irregular heartbeat, hand tremors, weight loss. It is also a cause of exophthalmos .

Hasimoto’s Thyroiditis: This is the most common cause of hypothyroidism. It is very similar to Grave’s Disease, but instead of making excessive amounts of thyroid hormone, the body make decreased amounts of thyroid hormone.

Thyroid Nodules: A thyroid nodule is a small lump on the thyroid gland that may be solid or a fluid-filled cyst. The overwhelming majority of these nodules are harmless. Occasionally, thyroid nodules can be cancerous and need to be treated.
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Thyroiditis: Thyroiditis is an inflammation of the thyroid gland. It may be associated with either hypo- or hyperthyroidism. It may be painful, feeling like a sore throat, or painless. Thyroiditis may be due to autoimmune activity, an infection, exposure to a chemical that is toxic to the thyroid, or an unknown cause.

Goiters: A t
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hyroid goiter is a visible enlargement of the thyroid gland. In the past, this condition was relatively common and was due to a lack of iodine in the diet. Iodine is a necessary component of thyroid hormone production. In the United States, where iodine is now routinely added to table salt (iodized) and used to clean milking cows’ udders, the incidence of dietary-related goiters has declined significantly. In other parts of the world, however, iodine-related goiters are still common and represent the most common cause of hypothyroidism in some countries. Goiters may compress vital structures of the neck, including the trachea and esophagus. This compression can make it difficult to breathe and swallow.


CAREER APPLICATION


Because endocrinology involves so many conditions and diseases, it is very important to those in the medical field to know in depth what endocrinology is and how it affects the processes of the body. It affects many of the organs of the body, such as the pituitary, thyroid, adrenals, ovaries, testes, and pancreas, so it is something a nurse would probably deal with an a very regular basis.




CASE STUDY


Andrea: The Death of a Diabetic


Case Study Questions:


1. What are the symptoms of diabetes?
Some of the symptoms of diabetes are frequent urination, unquenchable thirst, weight loss, weakness, fatigue, tingling or numbness in the hands, legs or feet, blurred vision, and dry, flaky skin.

2. What are the different types of diabetes?
The three main types of diabetes are type 1 diabetes, which is an autoimmune disease, type 2 diabetes, the most common form of diabetes, and gestational diabetes, developed in women during pregnancy.

3. What is known about the genetics of diabetic disorders?
Type 1 and type 2 diabetes have different causes. There are two factors that are important in both. You must inherit a predisposition to the disease, and something in your environment must trigger diabetes. Genes alone are not enough.
In most cases of type 1 diabetes, people need to inherit risk factors from both parents. Type 2 diabetes has a stronger genetic basis than type 1, yet it also depends more on environmental factors. Gestational diabetes is more puzzling. Women who get diabetes while pregnant are more likely to have a family history of diabetes, especially on their mother’s side. But like in the other forms of the disease, nongenetic factors also play a role. Older mothers and overweight women are more likely to get gestational diabetes.

4. What goes wrong when juvenile diabetes sets in?
If juvenile diabetes sets in and is left untreated, damage can occur to the eyes (leading to diabetic retinopathy and possible blindness), blood vessels (increasing the risk of heart attack and stroke), nerves (leading to foot ulcers, impotence, and digestive problems) and kidneys (leading to kidney failure).

5. What is known about the role that insulin plays in the processing of blood sugar?
Insulin has many effects on the blood glucose levels in our body. With increased levels of glucose in the blood, insulin is secreted from the pancreas. It is then release from the beta cells. This causes an increased uptake of glucose in the muscles, red blood cells, and fat cells. The increased uptake manages the glucose levels in the body. Another important role of insulin is the processing of various nutritional elements such as proteins and carbohydrates. It is also involved in amino acid transport.

6. What are the various treatments for the different diabetic conditions?
Treatment of all types of diabetes includes regular monitoring of blood sugar levels, following a well-balanced healthy diet and regular exercise. Type 1 diabetes is always managed with injected insulin. Type 2 diabetes and gestational diabetes are often managed with oral antidiabetic drugs, and some may even need insulin injections.



RESOURCES


Images
1: http://www.pituitarysociety.org/public/overview/normalpituitary?printablepage=1
2: http://www.nlm.nih.gov/medlineplus/ency/imagepages/17067.htm
3: http://alpine.websitewelcome.com/~answerco/7/pictures-of-thyroid-nodules.html
4: http://barbraschroeder.com/muhanadoela/goiter-images.html
Crossword Puzzle
http://www.proprofs.com/games/word-search/chemical-classification-of-hormones/
All information came from the above websites as well as Human Physiology, Stuart Ira Fox, 12th Edition; Burton’s Microbiology For The Health Sciences, Paul G. Engelkirk and Janet Duben-Engelkirk, 9th Edition; and www.webmd.com.