Pituitary Gland and its Control by the Hypothalamus. Dr Faghihi Professor of physiology

Transcription

1 Pituitary Gland and its Control by the Hypothalamus Dr Faghihi Professor of physiology

2 Objectives After studying this chapter, you should be able to describe: Structure of the pituitary gland Connections between hypothalamus and pituitary gland Hypophysiotropic hormones, and their effects on anterior pituitary function. Synthesis, processing, storage, and secretion of posterior pituitary hormones. Effects of ADH, it s receptors and how its secretion is regulated. Effects of oxytocin, it s receptors and how its secretion is regulated.

3 توجه نماييد تا آخر جلسه به اين سوال پاسخ دهيد: خانم 25 ساله اي با پرنوش ي و پر ادراري مراجعه كرده است. حجم ادرار 24 ساعته 12 ليتر و اسموالليته ادرار 220 مي باشد. شش ساعت بعد از تست water depriviation و از دست دادن 4 در صد وزن بدن اسموالليته ادرار 230 ميباشد. پس از تزريق DDAVP اسموالليته ادرار به 480 رسيده است. محتمل ترين علت چيست

4

5 small gland-about 1 centimeter in diameter

6 Embryologically, the two portions of the pituitary originate from different sources the posterior pituitary from a neural tissue the anterior pituitary from Rathke's pouch Downloaded from: StudentConsult (on 27 May :16 PM) 2005 Elsevier

7

8 Pituitary Gland It is often referred to as the master gland as it produces at least 10 hormones which influence the other endocrine glands. Anterior pituitary form a true endocrine gland and called adenohypophysis. posterior pituitary, also called neurohypophysis, is composed mainly of glial-like cells and terminal nerve endings.

9 The normal gross appearance of the pituitary gland The normal gross appearance of the pituitary gland removed from the sella turcica is shown here. The larger portion, the anterior pituitary (adenohypophysis), is toward the top. The image at the left shows the superior aspect of the pituitary with the stalk coming from the hypothalamus entering it. The inferior aspect of the pituitary is shown at the right. The.posterior pituitary (neurohypophysis) is the smaller portion at the bottom

10 Pituitary hormones

11 Hypothalamus Controls Pituitary Secretion

12 Specific Areas in the Hypothalamus Control Secretion of Specific Hypothalamic Releasing and Inhibitory Hormones

13 Hypothalamus

14 Magnocellular & Parvocellular neurons in the Hypothalamus

15 Hypothalamic-Hypophysial Portal Blood Vessels of the Anterior Pituitary Gland Figure 15.5

16 Hypothalamic Releasing and Inhibitory Hormones Are Secreted into the Median Eminence They Control Anterior Pituitary Secretion Thyrotropin-releasing hormone (TRH), which causes release of thyroidstimulating hormone (TSH) Corticotropin-releasing hormone (CRH), which causes release of adrenocorticotropin (ACTH) Growth hormone-releasing hormone (GHRH), which causes release of growth hormone (GH), and growth hormone inhibitory hormone (GHIH), also called somatostatin, which inhibits release of growth hormone (GH) Gonadotropin-releasing hormone (GnRH), which causes release of the two gonadotropic hormones, luteinizing hormone (LH) and folliclestimulating hormone (FSH) Prolactin inhibitory hormone (PIH), which causes inhibition of prolactin secretion

17 Specific Areas in the Hypothalamus Control Secretion of Specific Hypothalamic Releasing and Inhibitory Hormones

18

19 Posterior Pituitary Gland and Its Relation to the Hypothalamus Magnocellular neurons, located in the supraoptic and paraventricular nuclei of the hypothalamus Downloaded from: StudentConsult (on 27 May :16 PM) 2005 Elsevier

20 Posterior Pituitary Hormones Are Synthesized by Cell Bodies in the Hypothalamus

21 PreProADH PreProoxytocin ADH

22 Chemical Structures of Antidiuretic Hormone and Oxytocin (ADH)

23

24 Physiological Functions of Antidiuretic Hormone

25

26 In the presence of ADH, the permeability of the collecting ducts and tubules to water increases greatly and allows most of the water to be reabsorbed ADH (V 2, camp)

27 The osmolality establishes the driving force for osmotic reabsorption of water

28 Aquaporins (AQPs) in the principal cell of distal tubule

29 ADH Increases Water Reabsorption by AQP2

30

31 ADH (Vasopressin) Vasopressin (V 1, PLC)

32 Regulation of Antidiuretic Hormone Production Hyperosmolarity (1-2%) Hypophysis Decreased artrial volum ( 10-15%) (15-25%) Decreased arterial pressure (5-10%) (15%) Sympathetic stimulation Angiotensin II ADH Vasoconstriction Renal Fluid Reabsorption Increased Arterial Pressure Increased Blood Volum

33 Quantitative Importance of Osmolarity and Cardiovascular Reflexes in Stimulating ADH Secretion

34 Stimulation of ADH Release by Decreased Arterial Pressure and/or Decreased Blood Volume and/or Increased Extracellular Fluid Osmolarity

35

36 Estrogen Progesterone Sleep ANP body temperature

37 o Diabetes insipidus - Failure to Produce ADH: Central Diabetes Insipidus - Inability of the Kidneys to Respond to ADH: Nephrogenic Diabetes Insipidus o Syndrome of inappropriate ADH secretion (SIADH)

38 Oxytocic Hormone Oxytocin Causes Contraction of the Pregnant Uterus Oxytocin Aids in Milk Ejection by the Breasts

39 Possitive feedback effects of Oxytocin

40 Oxytocin causes contraction of myoepithelial cells in the alveoli of the mammary glands.

41

42

43 Oxytocin powerfully stimulates contraction of the pregnant uterus, especially toward the end of gestation Uterine contraction Di Stretching of cervix and vagina

44 Oxytocin What s the role of oxytocin in men?

45

46 با توجه به مطالب مطرح شده به اين سوال پاسخ دهيد: خانم 25 ساله اي با پرنوش ي و پر ادراري مراجعه كرده است. حجم ادرار 24 ساعته 12 ليتر و اسموالليته ادرار 220 مي باشد. شش ساعت بعد از تست water depriviation و از دست دادن 4 در صد وزن بدن اسموالليته ادرار 230 ميباشد. پس از تزريق DDAVP اسموالليته ادرار به 480 رسيده است. محتمل ترين علت چيست

47

48 Anterior Pituitary Gland

49 Objectives After studying this chapter, you should be able to describe: Cell types present in the anterior pituitary Hormones derived from the anterior pituitary Effects of growth hormone in growth and metabolic function, and how insulin-like growth factor I (IGF-I) may mediate some of its actions Regulation of Growth Hormone Secretion Basis of pituitary function abnormality and how they can be treated

50 سعي كنيد پس از اتمام جلسه درس به اين سوال پاسخ دهيد: خانم 44 ساله با آمنوره ثانويه گاالكتوره سردرد و اختالالت بينايي و هيپرپروالكتينميا به درمانگاه مراجعه نموده است. تست بارداري منفي و پروالكتين سرم او افزايش يافته است. پيش بيني شما چيست 50

51 Anterior Pituitary Gland and Its Relation to the Hypothalamus

52 Anterior Pituitary Gland Contains Several Different Cell Types That Synthesize and Secrete Hormones

53 Cell Types of Adenohypophysis

54

55 Hypothalamic Releasing and Inhibitory Hormones Control Anterior Pituitary Cells SS GHRH GnRH SS TRH DP CRH Somatotroph Gonadotroph Thyrotroph Lactotroph Corticotroph GH LH & FSH TSH PRL ACTH, β-lph, γ-lph and β-endorphin Somatostatin or GHIH Dopamine or PIH

56

57

58 Glycoprotein family

59 Pre pro opiomelanocortin POMC family

60

61

62 Biosynthesis of GH in the Somatotrope Cell hgh 191 AA t 1/2 < 20 min

63 Comparison of weight gain of a rat injected daily with growth hormone with that of a normal littermate Downloaded from: StudentConsult (on 27 May :16 PM) 2005 Elsevier

64 Lifetime pattern of GH secretion. GH levels are higher in children than in adults, with a peak period during puberty. GH secretion declines with aging

65 hch in Blood Circadian Rhythm of GH Sleep

66 Typical variations in GH secretion throughout the day, demonstrating the especially powerful effect of strenuous exercise

67 Some of the principal signaling pathways activated by the dimerized growth hormone receptor (GHR)

68 Growth Hormone Has Several Metabolic Effects (1) increased protein synthesis (2) increased use of fatty acids for energy (3) decreased glucose utilization

69 Growth Hormone Metabolic effects Proteins lipids Carbohydrates Growth effects Necessity of Insulin for the Growth-Promoting Action of GH

70 Effect of growth hormone, insulin, and growth hormone plus insulin on growth in a depancreatized and hypophysectomized rat

71 Factors that stimulate secretion of GH Decreased blood glucose Decreased blood free fatty acids Increased blood amino acids (arginine) Starvation or fasting, protein deficiency Trauma, stress, excitement Exercise Testosterone, estrogen Deep sleep (stages III and IV) Growth hormone-releasing hormone Ghrelin

72 Effects of fasting on GH secretion

73 Effect of protein deficiency on plasma GH and failure of carbohydrate treatment but the effectiveness of protein treatment in lowering GH concentration

74 Factors that inhibit secretion of GH Increased blood glucose Increased blood free fatty acids Aging Obesity Growth hormone inhibitory hormone (somatostatin) Growth hormone (exogenous) Somatomedin C (insulin-like growth factors-1, IGF-1)

75 Growth Hormone Exerts Much of Its Effect Through Intermediate Substances Called Somatomedins (Also Called Insulin-Like Growth Factors ) GH stimulates liver, cartilage, skeletal muscle and bone to produce Somatomedin (Somatomedin C or IGF-1) Most effects of GH are mediated indirectly by somatomedin C Direct action of GH promotes lipolysis and inhibits glucose uptake

76 Direct & Indirect Actions of GH Figure 15.6

77 Effects of GH & IGF-1

78 Complementary regulation of GH and insulin secretion coordinates availability of nutrients with anabolism and either caloric storage or mobilization

79 Short Duration of GH Action but Prolonged Action of IGF-1

80 Possible Role of Decreased Growth Hormone Secretion in Causing Changes Associated with Aging the average plasma concentration of GH 5 to 20 years 6 ng/ml 20 to 40 years 3 40 to 70 years 1.6 treatment of elderly patients with GH: insulin resistance and diabetes, edema, and joint pain. Therefore, GH therapy is generally not recommended for use in healthy elderly patients with normal endocrine function.

81 Hypothalamic signals depicting emotions, stress, and trauma can all affect hypothalamic control of growth hormone secretion

82 GH Stimulates Cartilage and Bone Growth (1) increased deposition of protein by the chondrocytic and osteogenic cells (2) increased rate of reproduction of these cells (3) a specific effect of converting chondrocytes into osteogenic cells thus causing deposition of new bone.

83 Effects of GH & IGF-1 on linear growth of long bone GH strongly stimulates osteoblasts

84 IGF-1 acts via autocrine & paracrine mechanisms to stimulate cell division

85 Relative importance of hormones in human growth at various ages

86

87 Abnormalities of Growth Hormone Secretion Dwarfism Decrease in GH Treatment with Human Growth Hormone Panhypopituitarism Levi-Lorain Panhypopituitarism in the adult Gigantism Acromegaly

88 Gigantism

89 Gigantism & Dwarfism

90 Acromegaly Downloaded from: StudentConsult (on 27 May :16 PM) 2005 Elsevier

91 Acromegaly

92 Charles Sherwood Stratton and Lavinia Warren Stratton Tom Thumb

93 با توجه به مطالب مطرح شده به اين سوال پاسخ دهيد: خانم 44 ساله با آمنوره ثانويه گاالكتوره سردرد و اختالالت بينايي و هيپرپروالكتينميا به درمانگاه مراجعه نموده است. تست بارداري منفي و پروالكتين سرم او افزايش يافته است. پيش بيني شما چيست 93

94