HORMONES and general knowledge of hormone for student

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1. SPECIAL TOPICS BCH 402 HORMONES

2. Millions of cells in the body need to communicate with each other. One method is through the nervous system: direct, fast and short acting Another is endocrine system using hormones: slow, indirect and last longer (hours, days, weeks) Endocrine system: is a complex system that helps maintain homeostatic environment in the body using hormones: A collection of glands and cells that produce hormones The term ‘endocrine’ implies that in response to specific stimuli, the products of those glands are released into the bloodstream. Endocrine system

3. Hormones are chemical molecules secreted by cells called endocrine glands The hormones are then carried via blood circulation to their target cells. Hormones are chemical messengers transported in the blood stream to perform biochemical/metabolic or physiological roles in distant areas of the body. Compounds that coordinate/interplay to affect activity of body tissues Some hormones affect only specific target cells, whereas other hormones affect numerous cell types throughout the body. Hormones

4. Some are activated by other hormones or neural effect While some hormones act directly to influence their target i.e tissues or metabolic processes Others called ‘tropic hormones’ are secreted to function in stimulating other target endocrine glands. Action of these latter hormones are usually controlled by a negative feedback mechanism. Factors such as stress, trauma, circadian rhythm, drugs influence synthesis and release of trophic hormones. Contd …….

5. Proteins and polypeptides: hormones secreted by anterior and posterior pituitary gland- pancreas and parathyroid gland Steroids: similar to cholesterol and are hydrophobic. Hormones secreted by adrenal cortex, ovary, testes Derivatives of amino acids: thyroid hormone (tyrosine) Structure and classification of hormones

6. Protein and polypeptide: synthesized by endocrine cells in endoplasmic reticulum DNA mRNAprotein in rough endoplasmic reticulum Synthesized as pre- prohormone  prohormone  active hormone Steroids-synthesized by cholesterol from tyrosine; in thyroid gland in thyroglobulin How are hormones synthesized

7. 1. Negative feedback-prevent overproduction/ overactivity of hormones Hormones of hypothalamus hormones of pituitary hormone of glands 2. circadian release of hormones- different amount released at different time of the day GH, thyrotrophin , gonadotropins max in early sleep cycle and low at the end of sleep cycle Cortisol increase in early morning hours gradually decrease during the day am and pm Regulation

8. In serum, hormones exist as free and bound to transport protein- sex hormone-binding globulin (estrogen and androgens), cortisol binding globulin ( cortisol ), thyroxine bidnding globulin, transthyretin ( thyroxine binding prealbumin ) Hydrophilic-peptides and catecholamine- dissolve in plasma easily as such transported in blood Hydrophobic- lipid soluble; steroid need a carrier protein to bind and transport them to target cells Receptors: located in cell membrane for hydrophilic hormones-signal molecules attach to receptor initiate series of events. Hydrophobic hormones can penetrate Phospholipid bilayer Transport

9. Down regulation-decrease number or affinity on target tissues-increase degradation, inactivation (decrease synthesis) Up regulation-increase number or affinity; increase synthesis and decrease degradation Regulation of receptors

10. Endocrine glands are glandular cells secreting hormones into the interstitial fluid, lymphatic system or blood Endocrine glands would secrete excessive or deficient amounts of hormones if abnormalities occur in target glands that produce the hormones. Endocrine glands

11. The hypothalamus is the part of the brain immediately above the pituitary gland and receives information from the rest of the brain. The hypothalamus controls the pituitary gland by secreting specific releasing and inhibitory factors which control the release of hormones from the pituitary gland-control center 6 hormones- Thyrotrophin releasing hormone Corticotrophin releasing hormone Growth hormone releasing hormone Growth hormone inhibiting hormone Prolactin inhibiting hormone Gonadotrophin releasing hormone HYPOTHALAMUS

12. Hypothalamic hormones stimulate the pituitary gland to release hormones 2 parts-anterior and posterior pituitary gland Anterior pituitary gland is connected to the hypothalamus through blood supply-hypothalamic hormones move through blood to stimulate release of hormones Posterior is connected to the hypothalamus through nerves-stimulate release through nerve signal Pituitary gland

13. Thyrotrophin releasing hormone stimulate release of thyroid stimulating hormone (TSH) Corticotrophin releasing hormone stimulate release of adrenocorticotrophic hormone (ACTH) Growth hormone releasing/inhibiting hormone stimulate release of growth hormone (GH) Prolactin inhibiting hormone controls prolactin (PRL) release Gonadotrophin releasing hormone stimulate release of gonadotrophins (FSH and LH) Anterior pituitary gland

14. Oxytocin - uterus contraction; muscle in breast to stimulate milk ejaculation Antidiuretic hormone (ADH)- vasopressin- stops water rehydration (urine production) during dehydration; maintain water concentration Posterior pituitary gland

15. Found in front of the trachea TSH- stimulate release of thyroxine (T4) and triiodothyronine (T3) Most of T4 is converted to T3 T4-20%; T3-80% Function: metabolism, development, catecholamine (neurotransmitters) release Calcitonin : a hormone released to decrease calcium in blood by decreasing reabsorption Synthesis-iodide in diet is absorbed in intestine and taken up by thyroid gland. Thyroid gland

16. Enzymes catalyze the iodination of tyrosine residues in glycoprotein; thyroglobin Iodide  iodine and thyroglobin is iodinated to form monoiodotyrosine (MIT) and diiodotyrosine (DIT) DIT + DIT= thyroxine DIT + MIT=T3 They stimulate protein synthesis and, like human growth hormone, are particularly important in stimulating growth of the skeleton. Hyperthyroidism- thyrotoxicosis ; commonest cause Graves disease (autoimmune disease; TSH ab ) Clinical feature- goitre : sweating, weight loss, fatigue, heart failure, high T3 and T4 serum levels Hypothroidism;myxoedema ; severe hypothyroidism (dryness of skin): cause Hashimotos thyroiditis (inflammation), autoimmune

17. Hypothalamus- corticotrophin releasing hormone Anterior pituitary- adrenocorticotrophin hormone (ACTH) 2 parts: cortex and medulla Cortex- glucocorticoids ( cortisol ), mineralocorticoids ( aldosterone ), androgens ( dihydrepiandrosterone sulphate DHAS) - ( aldosterone ) increase reabsorption of salt (Na) to increase blood volume  increase blood pressure -( cortisol ) increase blood glucose, suppress immune system, stimulate fight-flight Medulla- adrenalin and nor adrenalin Disorder: addison’s disease (adrenal hypofunction )- autoimmune Hyper function- cushing’s syndrome-excess glucocorticoids -cause adenomas and carcinoma Adrenal gland

18. GH is the most abundant of the pituitary hormones. As the name implies, it plays a pivotal role in controlling the body’s growth and development. For example, it stimulates the linear growth of the bones, promotes the growth of internal organs, fat (adipose) tissue, connective tissue, endocrine gland and muscle and controls the development of reproductive organs Growth hormone

19. In addition to its growth promoting role, GH affects carbohydrate, protein, and fat metabolism. Thus, GH increases the levels of the sugar glucose in the blood. GH also enhances the uptake of amino acids from the blood into cells as well as incorporation into proteins. GH modulates the activities of numerous target organs including liver, kidneys, bones, cartilage, skeletal muscle and adipose cells. The most important hormone controlling growth and development is growth hormone also known as somatotrophin which is secreted by the anterior pituitary gland. It also has an indirect effect by stimulating the release of small protein hormones called somatomedins from the liver. contd

20. Somatomedins , also known as insulin-like growth factors or IGFs because they resemble insulin in structure and in some aspects of function, mediate or regulate some of the effects of human growth hormone. Dwarfism: A deficiency of growth hormone, more properly called pituitary dwarfism to distinguish it from other causes. If the problem is due to growth hormone alone, then affected individuals do mature sexually. The dwarfism associated with African pygmies has been discovered to be due to a deficiency of one of the somatomedins , indicating the additional importance of these growth factors. contd

21. If over-produced human growth hormone occurs during childhood, when the bones are still capable of growth, the person becomes a ‘giant’, often reaching 8 feet in height (almost 2.5 metres ). The usual cause is a tumour of pituitary gland. If the condition occurs in adulthood, the bones are no longer capable of increasing in length, but can continue to grow in thickness, together with an increased growth of soft tissues. This results in a condition called acromegaly . Gigantism

22. Prolactin releasing hormone prolactin Stimulate lactation; milk production Disorder: deficiency: lactation failure Excess: amenorrhoea , infertility, galactorrhoea ; cause -pituitary tumor Prolactin

23. Gonadotrophin releasing hormone Anterior hormone- Follicle stimulating hormone and luteinizing hormone At the beginning of puberty they secrete sex hormones in response to signals from the pituitary gland and hypothalamus. Gonad- testes-LH stimulate leydig cells secrete testosterone FSH-stimulate Sertoli cells to produce androgens-together help sperm production and secondary sexual characters in males Ovaries-stimulated by LH produce progesterone and ovulation FSH stimulate follicle maturation which turn into oocyte (egg) Follicle maturation  oestrogen Gonads

24. In both sexes, these include small amount of both female and male sex hormones, oestrogens and androgens respectively. The androgens contribute to the adolescent growth spurt and development of pubic hair Hypoganodism - hypofunction of male gonads Klinefelter’s syndrome: small testes and abnormalities-additional X chromosomes 46 XXY Gynaecomastia - development of breast in males-balance between estrogens and androgens Female- menopause (last menstrual period), amenorrhoea and infertility, hirsutism and virilism (excess hair in women) disorder

25. Release parathyroid hormone Oppose the action of calcium; increase calcium in blood Parathyroid gland

26. Renin - works with aldosterone to increase blood pressure, blood volume Erythropoietin- increase red blood cell production since kidney need constant oxygen supply Kidney

27. Exocrine-chemical release into the duct Endocrine function-insulin- decrease blood glucose Glucagon- increase glucose level in blood Pancreas

28. Plant hormones are endogenous organic compounds active at very low concentration, produced in one tissue and translocated to another point in the plant where their effects on growth and development are manifested. Plant hormones are sometimes referred to as plant growth regulators (PGR) because they differ from animal hormones in the following ways PLANT HORMONES

29. Plant hormones are not made in specialized tissues. Plant hormones do not have specific target tissues. Plant hormones usually do not have specific effects. contd

30. Auxin (indoleacetic acid) Cytokinins (zeatin) Gibberellins (GA) Ethylene Others (jasmonic acid, brassinolide etc) Main types of plant hormones

31. Produced in apical and root meristems , young leaves and seeds in developing fruit. Functions Cell elongation and expansion Suppression of lateral bud growth Stimulation of abscission (young fruits) or delay of abscission. Hormone implicated in tropisms Auxin ( indoleacetic acid)

32. While other plant hormones are transported in the xylem or phloem, IAA is actively transported (faster than just by diffusion) through parenchyma tissue such as the cortex, the pith or the parenchyma cells associated with the vascular tissue. IAA moves down through the plant. Therefore it moves towards the base in shoots and towards the root tips in root (movement in specific direction is called polar movement). Transport of auxins

33. Cell elongation: IAA contributes to the growth of cells by loosening the cell wall. In general growth occurs by water uptake. In order for cell to enlarge the cell wall expand. IAA increases the extansibility of the cell wall, but its role in this process is not completely clear. It is likely that IAA turns on genes for the synthesis of new cell wall materials Effects of auxins in plants

34. Apical dominance The inhibiting effect of the shoot apical meristem on the growth of axillary buds is termed apical dorminace. It is thought that optimal concentration of IAA for axillary bud growth is much lower than what is produced by apical meristem; concentration both greater than or less than the optimal result in less growth. Other effects of auxins

35. Formation of adventitious roots When a leaf is excised from a plant and placed in a moist environment, the auxins produced by the leaf accumulate above the wound site. these relatively high levels of auxin which normally comes from the root, causes the plant to form roots at this location. contd

36. Leaf abscission Growing leaf produces IAA, but stress such as drought, cold or nutrient deficiencies cause the production of IAA to decrease. This decrease in IAA production causes ethylene production at the base of the petiole. In response walls of cells in the abscission zone become suberized and the middle lamella breaks down. contd

37. Herbicides The synthetic auxin 2,4-D(weed-B-Gon) is a cheap and relatively non- toxic herbicide that selectively kills broadleaf dicots contd

38. Applied as IBA, auxin conjugates ore mixes Stimulation of adventitious rooting 2,4 D as a herbicide for dicot Sprout prevention in pruned trees Fruit thinning or fruit holding Commercial uses of auxins

39. Produced in root meristems, young leaves, fruits and seeds. Functions Cell division factor Stimulates adventitious bud formation Promotes some stages of root development CYTOKININ (ZEATIN)

40. The structure of cytokinins is related to adenine, one of the four bases that are the key components of DNA. The naturally occuring cytokinin zeatin was isolated from corn (zea mays) in 1964. contd

41. Cell divison Cytokinins speed up the process of cell division, but this effect depends on the presence of auxins which are necessary for cell elongation. Organogenesis The balance of cytokinin and auxin in the growth medium of cultured cells has profound effect on whether root formation or shoot formation takes place. Effects of cytokinins in plant

42. If the ratio of cytokinin to auxin is high, shoots will form, and if low, root will form. Varying these ratios allows the formation of complete plants. The technique of micropropagation allow the selective production of plants with desirable traits. contd

43. Axillary bud growth in orchids, daylilies. Antioxidant (browing) preventer in cut salads. Mix with GA as fruit size stimulator. Commercial uses of cytokinins

44. Play a role in many functions associated with tissue elongation and phytochrome mediated responses. Although more than 80 different gibberellic acids (Gas) have been isolated from plants, most are inactive. Only GA1 is thought to control stem elongation in higher plants. GIBBERELLINS(1-80)

45. GAs are synthesized in immature seeds, the root and shoot apical meristems , and in young leaves. Transport Only auxins are transported in a polar fashion. GAs and other plant hormones (except ethylene, which is a gas) are transported in the xylem and phloem. contd

46. Cell division and elongation GAs increases plant height by increasing internode length. It can be applied to dwarf plants and cause them to attain normal height. Dwarf plants are not deficient in GA, but they don’t make enough of the active form of the hormone. GA differ from auxins in stimulating cell division as well as elongation. Effects of Gibberellic acids in plants

47. Seed germination In the cereal grain barley, the cotyledon produces GA when germination begins. GA is transported to the aleurone layer, alayer surrounding the endosperm cells that store starch. GA causes cells in the aleurone layer to produce enzyme amylase, which is secreted into the endosperm. contd

48. The amylase breaks the starch down to glucose, which can be used by the germinating seedling for growth. This process is well studied in barley because the malting step of brewing is the breakdown of starch in germinating barley seeds. Commercial breweries add GA to ensure complete starch breakdown. contd

49. Flowering Biennial plants may have short internodes their first year, then undergo internode elongation and flowering in year two. GA will substitute for a daylength response and probabily also for a cold temperature requirement and induce internode elongation if it is applied to the rosette form of plants. This permits seed production to be completed within one year. contd

50. Height control in flowering pot plants Height control in bedding plants Increase flower size on certain ornamentals. Increase berry separation and size in bunch grapes Stimulate seed germination. Commercial uses of GA

51. Gaseous hormone produced in many plant tissues. Functions Autocatlytic (stimulates its own production) Volatile gas Production stimulated during ripening, flooding, stress, senescence, mechanical damage, infection. Prodcution of combustion of petrochemicals Fruit ripening (with GA) Abscission (dropping) leaf, flower and fruits. ETHYLENE

52. Induces epinasty (down turning of leaves) (with auxin ). Promotes root hair elongation. Initiates germination in grains (corn) (with GA). Induces flowering in pineapple Promotes female expression in flowers contd

53. Fruit ripening Ethylene causes chlorophyll to break down and other pigments to form ( e.g the change in apple skin color with ripening). It also causes fruit softening by causing the production of the enzymes cellulase and pectinase which breaks down cellulose and pectin, structural components of the cell wall. Ethyelene also causes starches to be converted to sugars. Effects of ethyelene in plants

54. Fruits such as apples, bananas, kiwi, avocado and tomatoes can be stored under ethylene free, low oxygen conditions for months without ripening. When they are needed for market about 1 ppm ethylene is added to the air. These fruits experience a climateric which is an increase in respiration caused by production of ethylene by plant itself. contd

55. Abscission Ethylene production following a drop in IAA production by leaves causes the breakdown of the middle lamella and the suberization of cells in the absicission zone which is followed by leaf drop. contd

56. Removed by chemical scrubbing or low temperature Long term storage of apples Treatment of cut flowers with silver thiosulfate. Long keeper (delayed ripening) mutants of tomato Commercial use of ethylene

57. Applied as ethylene gas or ethephon Flower initiation Stimulation of ripening (bananas, tomatoes) Degreening of citrus Abscission induction prior to mechanical harvest (cherries) Increased color development in once over harvested processor type tomatoes contd

58. It is found in stressed leaves, dormant seeds and dormant buds. ABA was discovered as a contaminant and inhibitor of IAA from plant extracts. It was also present in high amounts in dormant buds. It was therefore at first named dormin . ABA is high in dormant buds, and purified ABA will cause dormancy when applied to other buds. ABSCISIC ACID (ABA)

59. ABA is used as a signal by plants under drought stress. Drought stressed leaves make large amounts of ABA which causes the stromata to close. Inhibits germination of some seeds (seed dormancy);plays a role in seed maturation and maturity. contd

60. Inhibits active growth of auxillary buds. Apical dorminace; inhibition of growth of lateral buds by the apical meristem; varies with plant species and plant age contd