Hormones

=Hormones =

**By Maurizio Camere (B.6.1 - B6.2) and Oliver Jurgensen (B.6.3 - B6.4) **
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The endocrine system is a set of organs (glands) that are formed by glandular cells, which have a larger volumetric space of cytoplasm compared to other cells as several metabolic reactions occur. They are positioned by groups or also known as lobules. The main characteristic of hormones is that they are mainly composed of polypeptides or proteins and serve as chemical messengers. They are secreted in to the blood for different purposes, and metabolized ferly quickly on the tissue they act upon. It is also important to mention that hormones do not create functions rather they trigger one. =====

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The main endocrine gland is the hypothalamus that is located in the base of the brain. The principal hypothalamic hormones are oxytocin (OXT), which is related to the sexual patterns, maternal and paternal behaviors, and also during labor to stimulate contractions. Prolactin (PRL), is a hormone related to the mammary tissue for the production of milk, when pregnant. Lastly it is the antidiuretic (ADH) hormone or also known as arginine vasopressin (AVP) that is produced by the hypothalamus but secreted by the hypophysis (as well as OXT), more specifically by the posterior lobe or also known as neurohypophysis. This hormone triggers one specific section of the kidney, located in the nephrons, the collecting duct to become more or less permeable to water. If the water levels in blood are low, ADH will be secreted and the collecting duct will develop aquaporins to absorbed water back to the blood, and when water levels are high ADH will not be secreted. =====

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The Pituitary gland or Hypophysis is the second main endocrine gland, it is located in the diencephalon and it is connected with the Hypothalamus by the median eminece. It is positioned in the sella turcica of the sphenoid bone and consists of two parts, the anterior lobe (adenohypophysis) and posterior lobe (neurohypophysis), which mainly secretes the hormones mentioned above. The main hormones that the anterior lobe secretes are the Thyroid- stimulating hormone, that act upon the Thyroid gland and stimulates the production of Thyroxine a iodated amino acid derivative. It is also secretes Gonadotropin Hormone A (FSH) and B (LH) that are vital during pregnancy. =====

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Other important hormones are estrogen and progesterone secreted by the ovaries that are very important during pregnancy. This is because estrogen in one side stimulates the thickening of the endometrium, stimulates Luteinizing Hormone secretion and also inhibits LH and FSH. Progesterone has similar functions as it maintain the endometrium wall, inhibits contractions, as well as FSH and LH secretion. The testicles and the Adrenal gland on the other hand secrete testosterone in the male reproductive system that stimulates the maturation of secondary spermatocytes into mature sperm cells as well as stimulating the development of male features: deepening of voice, development of male musculature, growth of hair on the face and other parts of the body. =====

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Other hormones could also include insulin that is made up of two polypeptide chains held together by disulfide bonds. It is secreted by the Pancreas to regulate glucose levels in the blood. When these levels are too high, the B-cells in the pancreatic islets secrete insulin that triggers liver and muscle cells to take up glucose from the blood and converted in to glycogen that then is stored as granule in cells. Epinephrine (adrenaline) is secreted by the Adrenal gland or also known as suprarenal glands, in the adrenal medulla, it regulates the function of organs under sympathetic control. Aldosterone is also secreted by the Adrenal gland more specifically in the adrenal cortex. It is a steroid hormone that plays a vital role in the kidney as it regulates the blood pressure that arrives from the afferent arteriole. Blood pressure is a main a factor in the filtration and reabsorption process in the nephron, as aldosterone acts on the distal tubules (reabsorption of glucose & ion salts) and collecting ducts (reabsorption of water). =====

**B.6.2 Compare the structures of cholesterol and the sex hormones **

 * Steroids: ** are a type of lipid, derived from cholesterol, they are hydrophobic, lipophilic (can cross membranes) and undergo constitutive secretion. Steroid hormones mode of action is as follows: They enter target cells through the plasma membrane, bind to receptor proteins in the cytoplasm and from a steroid/receptor complex, which affects gene expression. They can act directly as a transcriptional regulator.

//Structure:// consist of four contiguous carbon rings (the common backbone) -Different steroids have different functional groups attached to the backbone.


 * Cholesterol: ** most common steroid, an essential component of cell, brain and nervous tissue. It has a chain of alkanes on one ring, and a -OH group on the last ring. Some steroids act as hormones, which send chemical messages to different parts of the body; these hormones are synthesized from cholesterol in the ovaries, testicles, and other glands that produce them.




 * Progesterone: ** Carbonyl group (ring=O) attached to a methyl group on the first ring, carbonyl group (ring=O) on the last ring




 * Testosterone: ** -OH group on the first, ring=O on the last. Differences: cholesterol is primarily hydrophobic, with only one carbonyl group, the sex hormones have carbonyl groups and hydroxyl groups which make the molecule partly hydrophilic on both ends.



===**B.6.3 Oral contraceptives ( ****Describe the mode of action of oral contraceptives. ) **===

====Oral contraceptives have many different sizes and shapes but probably the most common one used is called the combined oral contraceptive pill. That pill contains a mixture of oestrogen and progesterone. Basically the pill has many functions and it works in a number of ways. For example, the first function that oral contraceptives have is that they prevent the release of an egg from the ovary. It can also change the release of certain hormones needed for pregnancy (FSH and LH). Another function that oral contraceptives have is that they prevent ovulation or egg release from the ovary. Furthermore, if the egg is already released, oral contraceptives can prevent the attachment of the egg to the uterus and basically that is because the endometrium lining happens to get thinner so that it become unsuitable for a fertilized egg to implant on the lining. Finally, the last effect of taking oral contraceptives is that they make the mucus in the cervix thicker and that is done so that it prevents sperm from reaching the egg If the combined oral contraceptive pill is taken correctly it can be 99% effective at preventing pregnancy.====



Combined Oral Contraceptive Pill:



===**B.6.4 Steroid use and abuse ( ****Outline the use and abuse of steroids) **=== ==== Steroids can normally be used on either a male or female that is having late puberty or has low muscles mass or bone mass. This is generally the best way to combat these deficiencies because steroids enlarge or increase the muscles and bones on the person who is taking them. It can also bring on puberty for those who have late puberty and are not experimenting any change. Steroids can normally be abused to further increase muscle mass and size but there are some side effects. Some side effects from these abuses could be breast growth in males as well as testicular shrinkage. In females, the worst side effect is breast reduction. Due to the increase in muscle and bone mass, muscles can grow more than the tendons and ligaments and that may cause them to snap. Finally, rage is another side effect that affects both genders. ====

Some Anabolic Steroids:

One of the methods to inject anabolic steroids:

Sources: [] (Information) [] (Effects of Oral Contraceptives) [] (Combined Oral Contraceptive Pill) [] (Steroids) [] (Steroids)