ENDOCRINOLOGY The scientific study of the endocrine glands and their hormones

1. ENDOCRINOLOGYThe scientific study of the endocrine glands and their hormones

2. THINGS NEED TO KNOW • General Features of the Endocrine System and Important definitions • Evolution of the Endocrine System • Classes of Hormones • Actions of Hormones

3. General Features of the Endocrine System • Endocrine glands are ductless • Endocrine glands have a rich supply of blood. • Hormones, produced by the endocrine glands are secreted into the bloodstream. • Hormones travel in the blood to target cells close by or far away from point of secretion. • Hormones receptors are specific binding sites on the target cell.

4. Important Definitions • What are hormones? Hormones are organic chemical messengers produced and secreted by endocrine cells into the bloodstream. Hormones regulate, integrate and control a wide range of physiologic functions.

5. Important Definitions Cont. • What are endocrine glands? Endocrine glands are ductless glands comprised of endocrine cells. This means that these glands do not have ducts that lead to the outside of the body. For example, sweat glands are NOT endocrine glands (they are instead exocrine glands) because sweat glands have ducts that lead to the outside surface of your skin (that’s how the sweat gets out). The fact that endocrine glands are ductless means that these glands secrete hormones directly into the blood stream (instead of to the outside of your body).

6. Important Definitions Cont. • What are target cells? Target cells refer to cells that contain specific receptors (binding sites) for a particular hormone. Once a hormone binds to receptors on a target cell, a series of cellular events unfold that eventually impact gene expression and protein synthesis.

7. Important Definitions Cont. • What are hormone receptors? Hormone receptors are binding sites on the target cell (either on the surface or in the cytoplasm or nucleus of the target cell) that are activated only when specific hormones bind to them. If a hormone does not/cannot bind to it’s receptor, then no physiologic effect results. See next slide for a picture of a hormone bound to its receptor

8. Growth hormone regulates cell growth by binding to growth hormone receptors on target cells.

9. THINGS NEED TO KNOW • General Features of the Endocrine System and Important definitions • Evolution of the Endocrine System • Classes of Hormones • Actions of Hormones

10. Evolution of the Endocrine System • It is likely that the vertebrate endocrine system evolved from bacterial signaling systems that allowed bacteria to both perceive extra- and intracellular signals. • Primitive endocrine signaling likely arose from cells releasing chemical signals to communicate with neighboring cells (paracrine signaling).

12. Classes of Hormones • Steroids vs. Peptide Hormones Hormones fall into 2 general classes based on their molecular structure and synthesis. • All steroid hormones are made initially from the precursor (precursor = first step in biosynthetic pathway) cholesterol. See next slide for a diagram of the biosynthetic pathway of steroid hormones from cholesterol.

14. Steroid Hormones • Steroid hormones are produced by the gonads and adrenal cortex. • Thyroid hormones are not steroids, but will be categorized with steroids for simplicity. • Steroid hormones are made from cholesterol in the smooth endoplasmic reticulum and mitochondria of endocrine cells.

15. Steroid Hormones • Steroid hormones cannot be stored in vesicles in the endocrine cells that produce them. As soon as steroid hormones are produced, they diffuse out of the endocrine cell and enter the bloodstream. • Steroid hormones are lipid soluble and their receptors are located inside their target cell.

17. Steroid hormones: Penetrate the cell and bind to a receptor protein inside the target cell. This also will trigger signal transduction pathway (for triggering mRNA transcription for synthesizing a specific protein). • Estrogen, progesterone, vitamin D and NO. • Usually, the intracellular receptor activated by a hormone is a transcription factor.

18. Peptide Hormones • Peptide hormones are comprised of chains on amino acids. • Like most proteins, peptide hormones are synthesized on ribosomes of the (rough) endoplasmic reticulum of endocrine cells. • Peptide hormones can be stored in vesicles in endocrine cells until they are needed at some later point.

19. Peptide Hormones • Peptide hormones do not readily pass through cell membranes (lipid bilayers) and they are referred to as water soluble. • Receptors for peptide hormones are found on the cell surface of their target cells.

21. Most chemical signals bind to plasma-membrane proteins, initiating signal-transduction pathways. Mechanism of chemical signaling: The chemical signals secreted by a cell either: Protein hormones: Bind to a receptor protein on the surface of the target cell whichwill trigger signal transduction pathway.

22. Actions of Hormones • Fetal development and differentiation • Cell growth and cancer • Metabolism • Cardiovascular function • Renal function • Skeletal function • Reproductive function • Immune function • Central nervous system function

23. Nervous and endocrine systems are the main internal communication and regulation systems. • The animal hormone-secreting cells constitute the endocrine system. • Hormone secreting organs are called Endocrine Glands (ductless glandsالغدد الصماء). • Hormone is a chemical signal secreted into blood stream and regulates communicating messages within the body. • Target cell is the site that reached by the hormone to which it responds. • Complete changes in the body is regulated by hormones (e.g. metamorphosis in insects). • Types of hormones are [Polypeptide H., Amino acid derivatives H or Steroid H.].

24. Tropic hormones:الهرمونات المحفزة (المنبهة)target other endocrine glands and are important to understanding chemical coordination. • Many endocrine organs contain specialized nerve cells called neurosecretory cells that secret hormones. • The hormone epinephrine has two functions: • As a hormone of the endocrine system. • As a signal in the nervous system. • Feedback is common in regulation the activity of both endocrine and nervous systems (homeostasis) (Fig. 45.1, page 956): • Calcitonin and parathyroid hormones play an important role in maintaining the concentration of the blood calcium constant. • They are secreted from thyroid and parathyroid glands respictively. • Hormones regulate the development of invertebrates (e.g. insects)

25. الصنوبرية النخامية الدرقية الكظرية The Vertebrate Endocrine System • Tropic hormones (الهرمون المنبه للغدد) • Target other endocrineglands and areimportant to understandingchemical coordination. • Human has 9 endocrine glands. Fig. 45.5, Page 960

26. The hypothalamus and pituitary integrate many functions of the vertebrate endocrine system • The hypothalamus integrates endocrine and nervous function. • Neurosecretory cells of the hypothalamus produce hormones. • Releasing hormones stimulate the anterior pituitary (adenohypophysis) to secrete hormones. • Inhibiting hormones prevent the anterior pituitary from secreting hormones. 1)- Pituitary gland:secrets 9 hormones( 7 hormones by the anterior part and 2 hormones by the posterior part).

27. A)- Anterior pituitary hormones. • Growth hormone (GH): a protein. • Stimulates growth and metabolism. • Secretion regulated by hypothalamic hormones. • Acts directly on tissues or acts viagrowth factors. • Gigantism:العملقة excessive GH during development. • Acromegaly: excessive GH production during adulthood. • Hypopituitary dwarfism القزمية: childhood GH deficiency. • Prolactin (PRL): a protein. • Stimulates milk production and secretion from mammary glandالغدد اللبنية. This secretion regulated by hypothalamic hormones. • Gonadotropins (Gonotropic محفز للمناسل): glyocoproteins. • Follicle-stimulating hormone (FSH). • Stimulates production of sperms and ova. • Secretion regulated by hypothalamic hormones. • Luteinizing hormone (LH) المُحفز لتكوين الجسم الأصفر. • Stimulates ovaries and testes. • Secretion regulated by hypothalamic hormones.

28. Thyroid-stimulating hormone (TSH): a glycoprotein. • Stimulates thyroid gland. • Secretion regulated by thyroxine in blood. • Secretion regulated by hypothalamic hormones. • Adrenocorticotropic hormone (ACTH): a peptide • Stimulates adrenal cortex secretion of glucocorticoids • Secretion regulated by glucocorticoids and hypothalamic hormones. • Melanocyte-stimulating hormone (MSH): a peptide. • May play a role in fat metabolism. • Endorphins: peptides. • Inhibit pain perception. • Effects mimicked by heroin and other opiate drugs.

29. Melanocyte-stimulating H. Adrenocorticotropic Also called gonadotropine hormones هرمونات المناسل The anterior pituitary gland hormones Fig. 45.6b, Page 963

30. B)- Posterior pituitary hormones. • Oxytocin: a peptide. • Stimulates contraction of the uterus and mammary glands. • Secretion regulated by the nervous system. • Antidiuretic hormone (ADH):مُضاد لإدرار البول a peptide. • Promotes retention of water by the kidneys (in Kidney tubules). • High level decreases urination and viceversa. • Secretion regulated by water/salt balance. • 2- Pineal gland:الغدة الصنوبرية is a small mass of tissue near the center of the mammalian brain and involved in biorhythms. • The pineal gland secretes the hormone, melatonin, an amine. • Involved in biological rhythms associated with reproduction. • Secretion regulated by light/dark cycles.

31. Antidiuretic H • Posterior pituitary(neurohypophysis)stores and secretes hormones produced by the hypothalamus.

32. Thyroid releasing H. Thyroid stimulating H. See Fig. 45.7, Page 965 3. Thyroid gland: secretshormones function in development, bioenergetics, and homeostasisثبات البيئة الفسيولوﭽـية الداخلية • The thyroid gland of mammals consists of two lobes located on the ventral surface of the trachea. It contains 4 small Parathyroid glands. It plays role in maintaining normal blood pressure, heart rate digestion ..etc. • Thyroid glands secretes 3 hormones: • Tri-iodothyronine[(T3), 3 I atoms]: amino acid derivative. • Thyroxine [(T4), 4 I atoms]:amino acid derivative. • Stimulates and maintain metabolic processes. • Secretion regulated by TSH hormones. Fig. 45.8, Page 965

33. Calcitonin:apeptide. • Lowers blood Ca2+ levels. • Its secretion regulated by calcium in blood. • Hyperthyroidism: the excessive secretion of thyroid hormones causes: • high body temperature • sweating • weight loss • Irritability • high blood pressure. • Hypothyroidism: an insufficientقليل amount of thyroid hormones because deficiency of I in human diet (causes Goiter). • Infants: cretinism. • Adults: weight gain, lethargy, cold intolerance. • Goiter تضخم الغدة: often associated with iodine deficiency نقص.

34. Parathyroid gland: Parathyroid hormone (PTH): a peptide • PTH is secreted byThe four parathyroid glands which embedded in the surface of the thyroid gland. It functions as: • Raises blood Ca2+ levels. • Secretion regulated by calcium in the blood. • Causes osteoclastsفقد الكالسيوم to break down bone, releasing Ca2+ into the blood. • Stimulates the kidneys to reabsorb تعيد إمتصاصCa2+. • Stimulates kidneys to convert vitamin D to its active form, which stimulate intestine to absorb Ca2+. • PTH and calcitonin are antagonistic متضادين hormones. ThusPTH and calcitonin regulate blood calcium level (important role in homeostasis). • Hypoparathyoidism(tetany): it is a lack of PTH which causes: • Ca2+levels in the blood drop. • Convulsive contractions of the skeletal muscles.

35. Hormonal control of Ca2+homeostasis in mammals blood Read carefully the caption of Figure 45.9, Page 967

36. 5.Pancreas: Endocrine tissues of the pancreas secrete insulin and glucagon, antagonistic hormones that regulate blood glucose • The pancreas has both endocrine and exocrine functions. • Exocrine function: secretion of bicarbonate ions and digestive enzymes. • Endocrine function: insulin and glucagon secreted by beta and alpha cells of islets of Langerhans جيوب لانجرانز. • Insulin:a protein secreted by beta cells. • Lowers blood glucose levels. • Stimulates all body cells (except brain cells) to take up glucose. • Slows glycogenolysis يبطىء تحلل الجليكوجين (a source of glucose). • Inhibits gluconeogenesis يوقف تكوين الجلوكوز. • Secretion regulated by glucose in blood (negative feedback). • Hypoinsulinism:diabetes mellitus نقص الإنسولين. • Hereditary factors عامل وراثى and play a role in its development. • High blood sugar levels – sugar excreted in the urine. • Symptoms: excessive urination كثرة التبول and excessive thirst العطش.

37. Type Idiabetes mellitus (insulin-dependent diabetes). • Autoimmune disorder. • Usually appears in childhood الطفولة. • Treatment: insulin injections. • Type IIdiabetes mellitus (non-insulin-dependent diabetes). • Usually due to target cells having a decreased responsiveness to insulin قلة الإستجابة للإنسولين. • Usually occurs after age 40 – risk increases with age. • Accounts for over 90% of diabetes cases. • Glucagon:a protein secreted by alpha cells. • Raises blood glucose levels. • Stimulates glycogenolysis تحلل الجليكوجين in the liver and skeletal muscle to produce glucose. • Secretion regulated by glucose in blood (negative feedback).

38. Fig. 45.10

39. 6. The adrenal gland:adrenal medulla and adrenal cortex help the body manage stress • The adrenal glands are located adjacent to the kidneys. • The adrenal cortexالقشرة is the outer portion. • The adrenal medulla is the inner portion. I- Adrenal medullaالمركز. • Developmentally and functionally related to the nervous system. • It producesthe following hormones (in response to stress): • Epinephrine (adrenaline هرمون القلب). • Norepinephrine (noradrenaline). They are amino acid derivatives (synthesized from tyrosine) and function as: • Raises blood glucose level and blood fatty acid level. • Increases heart rate and stroke volume and dilates bronchioles. • Shunts blood away from skin, digestive organs, and kidneys, and increases blood flow to heart, brain, and skeletal muscle.

40. II- Adrenal cortex: reacts to stress. • Secretion of corticosteroids (a family of steroid hormones) is regulated by the nervous system in response to stress for example: • Glucocorticoids. • Raises blood glucose level. • Secretion regulated by ACTH (Adrenocorticotropic hormone). • Abnormally high doses are administered as medication to suppress the inflammation response. • Mineralocorticoids (example: aldosterone, which affects salt and water balance). • Promotes re-absorption of Na+ and excretion of K+ in kidneys. • Their secretion regulated by K+ in blood. • A third group of corticosteriods are Sex hormones. • Androgens secreted by the adrenal cortex may account for the female sex drive. • The adrenal cortex also secretes small amounts of estrogens and progesterone.

41. Fig. 45.14

42. 7. Tests and ovaries:Gonadal steroids regulate growth, development, reproductive cycles, and sexual behavior • Testes hormones: • Testosterone): steroids. • Supports sperm formation. • Promote development and maintenance of male sex characteristics. • Secretion regulated by FSH and LH. • Ovaries hormones: • Estrogens: steroids. • Stimulate uterine lining growth. • Promote development and maintenance of female sex characteristics. • Secretion regulated by FSH and LH. • Progesterone: steroids. • Promotes uterine lining growth. • Secretion regulated by FSH and LH.

43. 8- Thymus gland: Secretes Thymosin: a peptide.It stimulates T lymphocytes. Protein hormones affect target cells via receptors on the membrane protein Steroid hormones inter the target cells and trigger protein synthesis via receptors in the nucleus.

44. Page 961

45. Table 45.1 (continued)

46. Many of the body's most basic functions are regulated by the endocrine system— eight different glands located PLZ OPEN THE VIDEO www.youtube.com/watch?v=kIPYVV4aThM

47. PLZ OPEN THE VIDEO www.youtube.com/watch?v=YiK8gHPYe6o Growth hormone (GH)

48. Some questions for More understanding

49. . • Q1: Write whether each of the following statements is True (T) or False (F): • 1-The adrenal gland is epinephrine source. • 2-Epinephrine and norepinephrine hormones are responsible for the "fight or flight" response to danger • 3-Luteinizing hormone (LH) stimulates hormone production by the ovaries and testes • 4-Posterior pituitary is endocrine organ that does not actually manufacture hormones but, rather, stores hormones produced elsewhere. • 5-The hypothalamus produces a releasing hormone that stimulates the pituitary to secrete GH. • 6-FSH (follicle-stimulating hormone) and LH (luteinizing hormone) are trophic hormones that are also known as gonadotropins.

50. The mammary glands of a pregnant female will begin to produce milk in response to changes in the level of prolactin  • High levels of T3 and T4 inhibit the secretion of TRH and TSH. • Pituitary dwarfism disorder is caused by hyposecretion of growth hormone. • When Ca2+ levels fall, PTH stimulates bone cells to decompose the matrix of bone and stimulates reabsorption of Ca2+ in the renal tubules. • Every time you eat a cookie or candy bar, your blood sugar increases. This triggers an increase in the hormone insulin