Pituitary Hormones

1. Pituitary Hormones

2. Growth Hormone (GH) • Also known as somatotropin • Gland Source = Adenohypophysis • Target = GH affects all cells, epiphyseal growth plate, skeletal muscles • Action = The three major ways it affects the body are: • Increase cell growth, mitosis, protein production • Simulates the epiphyseal growth plate (bones) & repair and maintenance of skeletal muscles • Encourage cells to use fats for fuel (gluconeogenesis: gluco=glucose; neo=new; genesis=to create • Stimulus for release=Hypothalamus releases GRH (Growth Release Hormone) • Inhibit=Hypothalamus will release GIH (Growth Inhibitory Hormone) • Problems: Pituitary Dwarfism, Low GH levels in adults, Pituitary Gigantism, And Acromegaly

3. Thyroid Stimulating Hormone (TSH) • Gland Source=Adenohypophysis • Target=Thyroid (makes sense…because the name of the hormone gives it away ) • Action=stimulates the thyroid to make and release thyroxin • Stimulus for release=Hypothalamus releases TRH (Thyroid Release Hormone) when the level of thyroid hormones decrease in the blood. • Inhibit-Negative Feedback Loop: When the hypothalamus detects an increase or normal levels of thyroid hormone in the blood, it will stop sending TRH.

4. Adrenocorticotropic Hormone (ACTH) • Gland Source=Adenohypophysis • Target=Adrenal cortex • Action=Stimulates the adrenal cortex to release corticosteroid hormones (Cortisol is the main one) to help the body resist stress. • Stimulus for release=Hypothalamus release CRH (Corticotropic Release Hormone). • Inhibit=Negative Feedback: An increase in levels of Cortisol in the blood causes the hypothalamus to decrease and/or stop CRH

5. Follicle Stimulating Hormone (FSH) • Gland source=Adenohypophysis • Target=Follicle egg maturation in the ovary; sperm production in the tubes of the testes (the testes are made up of 700 feet of seminiferous tubules!) • Action=This hormone’s primary function is to stimulate gamete (egg and sperm) formation. It can also help with the release of estrogen and testosterone from the gonads. • Stimulus for release=at the beginning of puberty and all through out the reproductive years, the Hypothalamus will release GnRH (Gonadotropin Releasing Hormone) • Inhibit= Negative Feedback: When the levels of estrogen & testosterone rise, the Hypothalamus decreases its release of GnRH.

6. Luteinizing Hormone (LH) • Gland Source=Adenohypophysis • Target=ovaries and testes (the interstitial cells) • Action=stimulates ovulation in the ovary. The ovulation process causes the release of progesterone (the other female hormone); the testosterone production in the testes. • Stimulus for release= Hypothalamus releases GnRH • Inhibit=Negative Feedback: As the level of progesterone and testosterone rise, the hypothalamus decreases its release of GnRH.

7. Prolactin (PRL) • Gland source=Adenohypophysis • Target=primary target is the mammary glands (breasts) • Action=stimulates the mammary glands (breasts) to produce milk in females; in males, it enhances the effects of ICSH (LH) • Stimulus for release=Hypothalamus releases PRF (Prolactin Release Factor). (Another Stimulus: when a mother is in the period of time that she is breast feeding her child, an infants feeding causes more milk to be made. As long as the infant breasts feed, the mother will make milk.) • Inhibit=Hypothalamus releases PRIF (Prolactin Release-Inhibiting Factor). It is not really understood what causes the hypothalamus control of this hormone. Some women who do not wish to continue or participate in breast-feeding, can ask their doctor for the latest treatment to inhibit milk production.

8. Melanocyte Stimulating Hormone (MSH) • Gland source=Adenohypophysis • Target=Melanocyte • Action=Stimulates the production of melanin to protect the skin from UV rays in fish, amphibians, reptiles, and other mammals. Its levels are too low in a human to have a significant effect. There are few times that MSH can affect humans: • In pregnant women • During fetal development • In very young children • In young children The reason some of these incidences occur is not understood. • Stimulus for release=Hypothalamus releases MRF (MSH-Releasing Factor) This release is thought to be caused by sunlight on the photosensitive receptors in the skin and eyes. • Inhibit=by the increase levels of dopamine (a hormone in the brain)

9. Oxytocin • Gland source=Neurohypophysis • Target=uterus wall (smooth muscle) and the breast area around the nipple (there is no known normal function of oxytocin in males.) • Action=causes strong (and I mean STRONG) uterine contractions [a.k.a labor contractions or labor pains] during birth). Oxytocin also stimulates the area around the nipples to eject milk. This really peaks after the birth of the child. • Stimulus for release=stretch receptors in the vagina and touch receptors around the nipples. • Oxytocin is a great example of a positive feedback loop during birth. • As the baby is pushed down the vaginal canal (also known as the birth canal), there is more and more stretching. This stretching causes more pain and stimulation to the hypothalamus, which in return sends more oxytocin.

10. Oxytocin (cont.) • Stimulus=Another stimulus for oxytocin is milk ejection. The ejection and flow of milk is known as lactation. This will continue as breast-feeding continues. • Inhibit=Once the stretching of the vaginal wall is finished, the hypothalamus will stop the release of oxytocin to the uterus. (Oxytocin will continue to the breast.) This takes a few days to come down and end with a negative feedback. • Problems: If a woman goes longer than expected in her pregnancy, her pregnancy can be induced with the synthetic form of oxytocin called Pitocin. Pitocin can also be used to increase the intensity of the contractions when a woman’s contractions are too weak or to control bleeding of the uterus after birth.

11. Endocrine Hormones

12. Antidiuretic Hormone • Anti=against; Diuretic=urine formation • This hormone hinders urine formation. • Gland source= Neurohypophysis • Target=kidney (more exactly, the distal end of the nephrons and collecting tubes.) • Action=instructs kidney (nephrons) to pull water out and place it into the blood (reabsorb). Instead of this water being a part of urine and going to the bladder to be excreted, it is placed back into the blood. • This hormone rehydrates us! • Stimulus for release=Dehydration • Inhibit=Hydrated (Hypothalamic osmoreceptors detect that the thickness of blood is normal.) • Problems: Diabetes insipidus

13. Triiodothyronine (T3) and Thyroxin (T4) • FOLLICLE HORMONE • Gland source=Thyroid gland (follicles) • Target=All body cells • Action=Accelerates the rate of cellular metaboloism (mitochondria breakdown of carbohydrates, rate of protein synthesis, and lipid breakdown) in every body cell • Stimulus for release=Low levels of T3 & T4 in the blood trigger the hypothalamus to release TRH, which causes TSH to be released and stimulate the thyroid. • Inhibit=Negative feedback (normal blood levels of T3 & T4 • Problems: • Hypothyroidism • Goiter • Cretinism • Myxedema • Hyperthyroidism: Grave’s disease

14. Calcitonin • PARAFOLLICULAR CELL HORMONE • Gland source=Thyroid gland (parafollicular cells) • Target= Osteoblasts and intestines • Action=Stimulates the osteoblasts to pull Ca++ from the blood and deposits into the bone (make bone tissue!) and causes a decrease in Ca++ absorption in the intestines. Job is simple to lower the blood Ca++ levels. • Stimulus for release=(Humoral) High blood Ca++ levels • Inhibit=Negative feedback (normal or low blood Ca++ levels) • Problems: Tetany, Osteitis Fibrosa Cystica

15. Parathyroid Hormone (PTH) • Gland source=Parathyroid Glands • Target=Three main targets: • Osteoclasts are stimulated to break down bone matrix and place Ca++ into the blood. • Instruct the kidneys to retain Ca++ and not allow it to be excreted. • Stimulate the skin to produce more Vitamin D to stimulate the intestines to absorb Ca++. • Action=All three targets help raise the blood Ca++ levels! • Stimulus for release= (Humoral) Low blood Ca++ levels stimulate production and release of PTH. • Inhibit=Normal (9-11mg/100ml of blood) levels of Ca++ or high levels of Ca++ (Negative feedback).

16. Aldosterone • Gland source=Adrenal cortex (Zona Glomerulosa) • Target= Kidney (distal tubule of the nephrons) • Action=instructs the reabsorption of Na+ (Which also causes water to be reabsorbed). This results in the not only increase of Na+ but also increases blood pressure. • Stimulus for release=Major regulation: Renin-Angiostensin System • Other stimulators: Low Na+ and High K+ levels and ACTH is released to increase blood pressure during times of stress. • Inhibit=High Na+ and Low K+ • ANF (Atrial Natriuetic Factor) This hormone is released by the heart when blood pressure goes to high. ANF inhibits Renin and Aldosterone.

17. Cortisol (Glucocorticoids) • Gland source=Zona Fasciculata of the Adrenal Cortex • Target=Adipose Tissue and Liver (these are the main targets) • Action=Gluconeogenesis (Gluco=glucose; neo=new; genesis=creation of something. “The creation of new sugar!”) • Cortisol causes glucose to be formed from the breakdown of fats and protein during tomes of long-term stress. This process helps keep the glucose level in the normal range during times of long term stress such as loosing a job, loved one, divorce, illness, and others • During a daily cycle, Cortisol is higher in the morning than in the evening. Handling stress in the morning seems to be much easier than later in the day. • High levels of cortisol (Glucocorticoids) can be used to act as an anti-inflammatory and Anti-histamine. • Stimulus for release=Stress • Inhibit=Negative feedback (no CRH from the Hypothalamus because stress level is low) • Problems: Cushing’s Disease, Addison’s Disease

18. Gonadocorticoids (Androgens) • Androgens develop mainly into male hormones and a very small amount into female hormones. • Gland source= Adrenal Cortex (Zona Reticularis) • Target=High levels occur mostly in the fetus and in early puberty, after this time has past, the gonads take over. • Action=Increases cell metabolism, red blood cell production in infants. In adult females, may play a role in the level of sex drive (libido) and provide some female hormones during menopause. In males, androgens may more or less effect amounts of body hair upon onset of puberty. • Stimulus for release=ACTH • Inhibit=Negative Feedback • Problems=In young men, a high amount of androgens can result in rapid sex characteristics and a very high sex drive. In young women, high levels of androgens can result in facial hair, and a male pattern of body hair distribution In some cases, the clitoris can grow to look like a small penis.

19. Epinephrine and Norepinephrine • Gland source=Adrenal Medulla • Target= Heart, blood vessels, respiratory system, liver, and skeletal muscles • Action=Increases blood sugar, blood pressure, heart arte, and blood flow to brain, heart, and skeletal muscles (vasodilation in these areas). Vasoconstriction to the skin and GI(gut) in order to redirect blood to the systems that can get you out of danger. Bronchi and bronchiole dilation to increase air exchange during the event. All this produces the “FIGHT OR FLIGHT” response! • Stimulus for release=Signals from the brain to the hypothalamus trigger the Sympathetic Nervous System, to activate the adrenal medulla. • Inhibit=Neural stimulation end and the liver and kidneys quickly remove these hormones from the body. This is a short term effect on the body.

20. Glucagon • Gland Source=Pancreas (Alpha Cells of Islet of Langerhans) • Target=Liver and Adipose tissue (fat) • Action= Instructs the Liver to change Glycogen into glucose (Glycogenolysis) [1 Glycogen molecule= 1,000,000 molecules of glucose; -olysis=break down] Glycogenolysis=breaking glycogen down in to glucose Glucagon causes glucose to be formed from the breakdown of fats and protein to raise blood sugar into the normal range. • Stimulus for release= low blood sugar (humoral response) • Inhibit=high blood sugar (negative feedback)

21. Insulin • Gland source= Pancreas (Beta Cells of Islet of Langerhans) • Target=all body cells (liver, kidney, and brain does not need insulin) • Action=Insulin stimulates the cells: • Respiration of glucose into ATP • Excess glucose is turned into glycofen (Glycogenesis) • When the glycogen storage is full, excess glucose is turned into fat • Amino acids are taken in for protein synthesis (repair & growth) • Free fatty acids (tails of the triglyceride) are covered into lipids • Stimulus for release=high blood sugar (glucose), amino acids, and fatty acids (humoral control) • Inhibit=negative feedback (low blood sugar, amino acids, and fatty acids • Problems: Diabetes mellitus

22. Estrogen • Gland source=ovaries • Target=Most body cells and the female’s reproductive organs. • Action=Development of secondary sex characteristics (female), supports the egg (oocyte) maturation, and works with progesterone for breast development and the menstrual cycle. • Stimulus for release=FSH and LH • Inhibit=Negative feedback

23. Progesterone • Gland Source=ovaries (corpus luteum) • Target=uterus and breast (mammary glands) • Action=Prepares the lining (endometrium) or the uterus for a fertilized egg and causes swelling in the breasts (PRL works here with progesterone) • Stimulus for release=LH • Inhibit=Negative feedback

24. Testosterone • Gland source=Testes (interstitial cells) • Target=Most body cells and seminiferous tubules • Action=Stimulates the production of sperm (spermatogenesis), secondary male sex characteristics, promotes protein synthesis in skeletal muscle (repair and maintained of the muscle). • Stimulus for release=LH • Inhibit=Negative feedback • Problems=There are many major health problems with the use of this ‘extra’ testosterone: the negative feedback to the testes causes them to stop producing their own testosterone, which can lead to testicular atrophy. Testosterone is an aggressive hormone and adding more of this hormone to the body can cause extreme aggressive behavior. This hormone causes major internal organs to enlarge, and other major problems that can lead to a life-threatening situation.