The endocrine system
Two body systems control all physiologic processes via a process of messaging-the nervous system with its electrical point-to-point control via nerves, and our system of interest-the endocrine system.
The endocrine system broadcasts its messages via chemical means, that being hormones, to essentially all cells through passage by blood and extracellular fluid. There are a variety of different hormones, and each one usually affects only a limited number of cells. Those specific cells are called target cells. A target cell responds to a particular hormone because it contains receptors for the hormone. These receptors located on the surfaces of many of the target cells. When a hormone is accepted by the many receptor sites, the hormone enters the cell and causes reactions specific to that tissue or organ.
The endocrine system is controlled by the pituitary gland. This master gland, in turn, is controlled by a brain region called the hypothalamus. This brain structure regulates releasing factors into a special blood vessel network called the hypothalamic-hypophyseal portal system. These releasing factors then cause or inhibit the release of pituitary hormones which travel via the circulatory system to the target organ.
Certain pituitary hormones are called gonadotropins-the term drawn from the fact that they stimulate the gonads - in males, the testes, and in females, the ovaries. It is the regulation of some of these endocrinologic process that allows for the myriad of changes throughout the body during the course of a successful feminizing regimen. In addition to gender based characteristics, hormones control and regulate a wide range of bodily activity necessary for our good health:
Pituitary Gland
Parathyroid Gland
Thyroid Gland
Thymus Gland
Adrenal Glands
Pancreas Gland
Ovarian Glands
Testicular Glands
Pituitary Gland
The pituitary gland is pea-sized structure located at the base of the brain and consists of two lobes. The pituitary gland is often portrayed as the master gland of the body. This reference is justified in the sense that the anterior and posterior pituitary lobes secrete a battery of hormones that collectively influence all cells and affect virtually all physiologic processes.
But the power behind these processes is the brain's hypothalamus, crucial in the regulation of body temperature, certain metabolic processes, and other autonomic activities. The hypothalamus and its releasing and inhibiting hormones directly influences the anterior pituitary hormones. The following table summarizes the major hormones synthesized and secreted by the pituitary gland. Contained within the table are the gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
| Hormone | Target organs | Physiologic Effects |
ANTERIOR PITUITARY |
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| Adrenocorticotropic hormone | Adrenal gland (cortex) | Stimulates secretion of glucocorticoids |
| Follicle stimulating hormone (FSH) | Ovary and testis | Control of reproductive function |
| Growth hormone | Liver, adipose tissue | Indirectly promotes growth, control of protein, lipid and carbohydrate metabolism |
| Luteinizing hormone (LH) | Ovary and testis | Control of reproductive function |
| Prolactin | Mammary gland | Milk production |
| Thyroid-stimulating hormone | Thyroid gland | Stimulates secretion of thyroid hormones |
POSTERIOR PITUITARY |
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| Antidiuretic hormone | Kidney | Conservation of body water |
| Oxytocin | Ovary and testis | Stimulates milk ejection and uterine contractions |
| Oxytocin | Ovary and testis | Stimulates milk ejection and uterine contractions |
Parathyroid Gland
The parathyroid gland is any of four small endocrine glands lying near the thyroid and producing hormones that regulate calcium and phosphorus metabolism. The parathyroid glands affect skeletal development.
Thyroid Gland
The thyroid gland is located in the neck, close to the Adam's apple. This gland has an influence upon metabolism, growth and maintenance of body tissues, and aspects of reproduction in the genetic female.
Thymus Gland
The thymus gland is located in the upper chest under the breastbone. This gland is the central control organ for the immune system. When it is functioning properly, the thymus gland acts like a thermostat to provide the right balance of immunity. It turns up to help the body fight infection or tumor and down to prevent autoimmune disease.
Adrenal Glands
The adrenal glands are two in number and are located on the top of each kidney. These glands are responsible for glucose metabolism, water and electrolyte balance, and produce small amounts of the sex hormones, estrogen and testosterone, in both genders.
Pancreas Gland
The pancreas is a long, tapered gland which lies across and behind the stomach. This gland secretes digestive juices which break down fats, carbohydrates, proteins and acids. Some cells in the pancreas secrete hormones which regulate the level of glucose in the blood.
Ovarian Glands
The ovary (pl., ovaries) is either of two organs found in the female reproductive tract in which ova form and which is responsible for the production of the hormones, estrogen and progesterone. These hormones cause the genetic female's secondary sexual characteristics to develop. The ovaries are responsible for ova (pl. of ovum) production, the female reproductive cell or egg.
Testicular Glands
The testis (also, testicle; pl., testes, testicles) is either of two primary male reproductive organs that produce both sperm cells and the male's major sex hormone, testosterone. The testes are located in a sac called the scrotum, which is located below the penis.