Hypophysis (Pituitary Gland)

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Hypophysis (Pituitary Gland)

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  • The pituitary gland, also called hyphophysis is a small gland that lies in the salla turcica, a bony cavity at the base of the brain. The pituitary gland or hypophysis is derived from two embryologically-distinct tissues. As such, it is composed of both neural and glandular tissue. Both tissues produce hormones that affect a large number of physiological processes.
  • As suggested by its Greek derivation, the hypothalamus (hypo = below, thalamus = bed) is that portion of the diencephalon in all vertebrates that lies inferior to the thalamus.
  • The hypothalamus lies directly above the pituitary gland and occupies approximately 2 per cent of the brain volume. The external surface of the hypothalamic floor gives rise to a median protuberance called the tuber cinereum (or gray swelling due to the pale bluish color of the blood vessels seen in the postmortem human brain), whose central part extends anteriorly and downward into a funnel-like process, the infundibulum or median eminence. The infundibulum is in direct continuity with the infudibular stem of the posterior pituitary gland, and together with the pars tuberalis of the anterior pituitary, forms the pituitary stalk. The dura mater completely lines the sella turcica and nearly surrounds the gland.
  • Note the high intensity or "bright spot" of the posterior pituitary by MRI in (A), sharply defining the boundary between the anterior pituitary gland. III = third ventricle
  • The cavernous sinus contains the internal carotid artery and cranial nerves III, IV, V1, V2, and VI. The optic chiasm resides immediately above the pituitary gland and is separated from it by a cerebrospinal fluid-filled cistern.
  • The hypothalamus is a region of the brain that controls an immense number of bodily functions. It is located in the middle of the base of the brain, and encapsulates the ventral portion of the third ventricle. The pituitary gland, also known as the hypophysis, is a roundish organ that lies immediately beneath the hypothalamus, resting in a depression of the base of the skull called the sella turcica ("Turkish saddle"). In an adult human or sheep, the pituitary is roughly the size and shape of a garbonzo bean.
  • Careful examination of the pituitary gland reveals that it composed of two distinctive parts: - =The posterior pituitary (neurohypophysis) is not really an organ, but an extension of the hypothalamus. It is composed largely of the axons of hypothalamic neurons which extend downward as a large bundle behind the anterior pituitary. =It also forms the so-called pituitary stalk , which appears to suspend the anterior gland from the hypothalamus.
  • The anterior lobe of the oituitary gland, the adenohypophysis, is derived from the primitive gut by upward extension of the epithelium of the primitive mouth cavity (stomodeum). -
  • - The adenohypophysis is derivative of buccal ectoderm. - The neutal lobe, the neurohypophysis, develops as a downward evagination of the neural tube at the base of the hypothalamus (infundibulum) and, therefore, represent a true extension of the brain. The neurohypophysis is a derivative of neural actoderm.
  • The pituitary gland or hypophysis is derived from two embryologically-distinct tissues. Microscopically, the anterior pituitary is composed of nests or cords of cuboidal cells organized near venous sinusoids lined with a fenestrated epithelium into which secretory products from the anterior pituitary are collected. Classically, five cell types and six secretory products of the anterior pituitary gland can be identified immunocytochemically including the somatotrophs (growth hormone), lactotrophs (prolactin), corticotrophs (adrenocorticotropic hormone), thyrotropes (thyroid-stimulating hormone), and gonadotrophs (luteinizing hormone and follicle-stimulating hormone). It is now recognized, however, that the anterior pituitary is vastly more complicated. In addition to morphological and physiological evidence for heterogenity among the classical anterior pituitary cell types and the presence of clusters of a unique cell type, the folliculostellate cell, the anterior pituitary can also synthesize numerous other nonclassical peptides, growth factors, cytokines, binding proteins and neurotransmitters listed in Table 2 that are important for paracrine and/or autocrine control of anterior pituitary secretion and/or cell proliferation under defined physiological conditions.
  • The bulk of the adenohypophysis is pars distalis. That tissue is composed of winding cords of epithelial cells flanked by vascular sinusoids. In sections stained with dyes such as hematoxylin and eosin, three distinct cell types are seen among epithelial cells: Acidophils have cytoplasm that stains red or orange Basophils have cytoplasm that stains a bluish color Chromophobes have cytoplasm that stains very poorly The figure below shows pars distalis from a cat at two magnifications
  • Acidophils Cells that contain the glycoprotein hormones: Somatotropes which produce growth hormone Lactotropes which produce prolactin Basophils Cells that contain the glycoprotein hormones: Thyrotropes which produce thyroid stimulating hormone Gonadotropes which produce luteinizing hormone or follicle-stimulating hormone Corticotropes which produce adrenocorticotrophic hormone Chromophobes These are cells that have minimal or no hormonal content.
  • Dominant featurec of the posterior lobe are the neurosecretory neurons that form the magnocellular neurosecretory system. These unmyelinated nerve tract arise from the supraoptic and paraventricular nuclei within the ventral diencephalon and descend through the infiundibulum snd neural stalk to terminate in the posterior lobe. The posterior lobe and median eminence are storage and secretory sites for hormones and, therefore, the posterior lobe is not corectly termed an endocrine gland.
  • The bulk of the neurohypophysis is composed on largely unmyelinated axons from hypothalamic neurosecretory neurons. These axons have their cell bodies in the paraventricular and supraoptic nuclei of the hypothalamus. These neurons secrete antidiuretic hormone or oxytocin .
  • The pars intermedia is closely associated with pars nervosa and separated from the pars distalis by the hypophyseal cleft. This lobe of the pituitary shows considerable variation in size among species.
  • The pars distalis of the anterior pituitary gland receives little or no arterial blood supply from branches of the internal carotid artery, while the posterior pituitary is fed by an anastomotic arterial circle derived from each of the inferior hypophysial arteries as they pierce the cavernous sinus. Rather, the pars distalis is supplied by venous blood delivered through the long portal veins that descend along the ventral surface of the pituitary stalk and interconnect capillary beds in the pars distalis with specialized capillary beds of the portal capillary system in the base of the hypothalamus called the median eminence. In turn, the portal capillary plexus in the median eminence receives arterial blood from a separate branch of the internal carotid artery, the superior hypophysial artery, after the internal carotid artery ascends from the cavernous sinus. In addition to venous blood draining from the hypothalamus, the pars distalis also receives venous blood draining from the posterior pituitary through the short portal vessels, giving rise to approximately 30 per cent of the total blood supply to the anterior pituitary. Venous drainage from the anterior pituitary to the systemic circulation is through adenohypophyseal veins located at a sulcus separating the anterior pituitary from the posterior pituitary. Other than the short portal vessels, venous drainage from the posterior pituitary collects into neurohypophyseal veins, which together with adenohypophyseal veins, extend as common vessels (confluent pituitary veins) to the cavernous sinus.
  • Gigantisms is characterized by excesive growth of the long bones. Patients maz growth to heights of as much as 260 cm.
  • Disease States The most common disease of man and animals related to antidiuretic hormone is diabetes insipidus . This condition can arise from either of two situations: Hypothalamic ("central") diabetes insipidus results from a deficiency in secretion of antidiuretic hormone from the posterior pituitary. Causes of this disease include head trauma, and infections or tumors involving the hypothalamus. Nephrogenic diabetes insipidus occurs when the kidney is unable to respond to antidiuretic hormone. Most commonly, this results from some type of renal disease, but mutations in the ADH receptor gene or in the gene encoding aquaporin-2 have also been demonstrated in affected humans. The major sign of either type of diabetes insipidus is excessive urine production. Some human patients produce as much as 16 liters of urine per day! If adequate water is available for consumption, the disease is rarely life-threatening, but withholding water can be very dangerous. Hypothalamic diabetes insipidus can be treated with exogenous antidiuretic hormone.
  • In years past, oxytocin had the reputation of being an "uncomplicated" hormone , with only a few well-defined activities related to birth and lactation. As has been the case with so many hormones, further research has demonstrated many subtle but profound influences of this little peptide. Nevertheless, it has been best studied in females where it clearly mediates three major effects:
  • As has been the case with so many hormones, further research has demonstrated many subtle but profound influences of this little peptide. Nevertheless, it has been best studied in females where it clearly mediates three major effects: Stimulation of uterine smooth muscle contraction at birth: At the end of gestation, the uterus must contract vigorously and for a prolonged period of time in order to deliver the fetus. During the later stages of gestation, there is an increase in abundance of oxytocin receptors on uterine smooth muscle cells, which is associated with increased "irritability" of the uterus (and sometimes the mother as well). In cases where uterine contractions are not sufficient to complete delivery, physicians and veterinarians sometimes administer oxytocin ("pitocin") to further stimulate uterine contractions - great care must be exercised in such situations to assure that the fetus can indeed be delivered and to avoid rupture of the uterus.
  • Stimulation of milk ejection (milk letdown): Milk is initially secreted into small sacs within the mammary gland called alveoli, from which it must be ejected for consumption or harvesting. Mammary alveoli are surrounded by smooth muscle (myoepithelial) cells which are a prominant target cell for oxytocin. Oxytocin stimulates contraction of myoepithelial cells, causing milk to be ejected into the ducts and cisterns. Establishment of maternal behavior: Successful reproduction in mammals demands that mothers become attached to and nourish their offspring immediately after birth. It is also important that non-lactating females do not manifest such nurturing behavior. The same events that affect the uterus and mammary gland at the time of birth also affect the brain. During parturition, there is an increase in concentration of oxytocin in cerebrospinal fluid, and oxytocin acting within the brain plays a major role in establishing maternal behavior.
  • Hypophysis (Pituitary Gland)

    1. 1. Taradi 1interactive physiology hypophysis PITUITARY GLANDPITUITARY GLAND (HYPOPHYSIS)(HYPOPHYSIS) Prof. Milan Taradi, MD, PhD Department of Physiology and Immunology Medical Faculty, Zagreb
    2. 2. Taradi 2interactive physiology hypophysis Pituitary Hormones and Their TargetsPituitary Hormones and Their Targets o At the size of a pea, the pituitary gland rules as the bandmaster in orchestra of all glands. o The hypothalamus is the true “master gland”.
    3. 3. Taradi 3interactive physiology hypophysis Three Levels of Endocrine ControlThree Levels of Endocrine Control IntegrationIntegration o Hormones of the hypothalamic- anterior pituitary pathway. o Hypothalamus pituitary trophic hormone pathways coordinate endocrine regulation.
    4. 4. Taradi 4interactive physiology hypophysis Gross anatomyGross anatomy o The pituitary gland is a small gland about o 1 centimeter in diameter and o 0.5 to 1 gram in weight.
    5. 5. Taradi 5interactive physiology hypophysis MidsaggitalMidsaggital SSection of theection of the HHumanuman BBrainrain o Midsaggital section of the human brain (from the XIX century wax collection of human brains at the Museum of the Department of Human Anatomy of the Unversity of Bologna, Italy). o The hypothalamus (asterisk) lies above the pituitary gland (cross).
    6. 6. Taradi 6interactive physiology hypophysis Magnetic Resonance ImageMagnetic Resonance Image o MRI (A) and corresponding schematic illustration (B) of the human hypothalamus (H) and pituitary gland seen in saggital orientation.
    7. 7. Taradi 7interactive physiology hypophysis Magnetic Resonance ImageMagnetic Resonance Image o MRI (A) and schematic image (B) of the pituitary fossa and its anatomic relationships seen in coronal orientation.
    8. 8. Taradi 8interactive physiology hypophysis Anatomy of theAnatomy of the PPituitaryituitary GGlandland o The pituitary gland is a roundish organ that lies immediately beneath the hypothalamus, resting in a depression of the base of the skull called the sella turcica ("Turkish saddle"). o In an adult human the pituitary is roughly the size and shape of a pea.
    9. 9. Taradi 9interactive physiology hypophysis Gross AnatomyGross Anatomy o The anterior pituitary (adenohypophysis) is a classical gland composed predominantly of cells that secrete protein hormones. o The posterior pituitary (neurohypophysis) is an extension of the hypothalamus and it is composed largely of the axons of hypothalamic neurons which extend downward as a large bundle behind the anterior pituitary. o It also forms the so-called pituitary stalk, which appears to suspend the anterior gland from the hypothalamus.
    10. 10. Taradi 10interactive physiology hypophysis Pituitary DevelopmentPituitary Development o The boundary epitheilal ectoderm in the roof of the pharynx forms a pocket (Rathke's pouch) that comes into contact with the ectoderm of developing brain.
    11. 11. Taradi 11interactive physiology hypophysis Pituitary DevelopmentPituitary Development o The anterior pituitary originates from the epitheilal ectoderm. o The posterior pituitary originates from the brain neuroectoderm.
    12. 12. Taradi 12interactive physiology hypophysis Microscopic AnatomyMicroscopic Anatomy o The pituitary gland or hypophysis is derived from two embryologically- distinct tissues: o the anterior lobe o the intermediate lobe o the posterior lobe
    13. 13. Taradi 13interactive physiology hypophysis Histology of theHistology of the AdenohypophysisAdenohypophysis o Three distinct cell types are seen among epithelial cells: o Acidophils have cytoplasm that stains red or orange. o Basophils have cytoplasm that stains a bluish color. o Chromophobes have cytoplasm that stains very poorly.
    14. 14. Taradi 14interactive physiology hypophysis The Adenohypophyse ContainsThe Adenohypophyse Contains Several Different Cell TypeSeveral Different Cell Type o Acidophils o Somatotropes which produce growth hormone o Lactotropes which produce prolactin o Basophils o Thyrotropes which produce thyroid stimulating hormone o Gonadotropes which produce luteinizing hormone or follicle-stimulating hormone o Corticotropes which produce adrenocorticotrophic hormone o Chromophobes o These are cells that have minimal or no hormonal content.
    15. 15. Taradi 15interactive physiology hypophysis Histology of theHistology of the NeurohypophysisNeurohypophysis o The large numbers of axons are observed, sprinkled with glial cells and capillaries.
    16. 16. Taradi 16interactive physiology hypophysis Posterior Pituitary Hormons are SynthesizedPosterior Pituitary Hormons are Synthesized by Cell Bodies in the Hypothalamusby Cell Bodies in the Hypothalamus o The bulk of the neurohypophysis is composed on largely unmyelinated axons from hypothalamic neurosecretory neurons. o These axons have their cell bodies in the paraventricular and supraoptic nuclei of the hypothalamus. o These neurons secrete: o antidiuretic hormone o oxytocin.
    17. 17. Taradi 17interactive physiology hypophysis Histology of the ParsHistology of the Pars IntermediaIntermedia o The pars intermedia contains large pale cells that often surround follicles filled with ill-defined "colloid". o It is small in man, but much larger in species such as amphibians. o Melanocyte- stimulating hormone is the predominant hormone secreted by the pars intermedia.
    18. 18. Taradi 18interactive physiology hypophysis The Hipothalamus Controls PituitaryThe Hipothalamus Controls Pituitary SecretionSecretion o Secretion by the anterior pituitary is controled by hypothalamic releasing (RH) and inhibitory hormones (IH). o RH ang IH are conducted to the anterior pytuitary through minute blood vesels called hypothalamic- hypophysial portal vessels. o Secretion from the posterior pituitary is controlled by nerve signals that originate in the hypothalamus.
    19. 19. Taradi 19interactive physiology hypophysis Hypothalamic RH and IH ControlHypothalamic RH and IH Control Anterior Pituitary SecretionAnterior Pituitary Secretion o Growth hormon releasing hormone (GHRH) o Thyreotropin-releasing hormone (TRH) o Corticotropin-releasing hormone (CRH) o Gonadotropin-releasing hormone (GnRH) o Prolactin inhibitory hormone (PIH) There are many additional hypothalamic hormones. The specific loci of the neuronal cell body that form the different RH and IH are still poorly known.
    20. 20. Taradi 20interactive physiology hypophysis PituitaryPituitary HormonesHormones and Theirand Their TargetsTargets o ACTH o TSH o GH o PRL o FSH o LH o MSH o ADH o Oxitocin
    21. 21. Taradi 21interactive physiology hypophysis Function of theFunction of the PPituitaryituitary GGlandland o Each lobe of the pituitary gland produces certain hormones. o anterior lobe: o growth hormone (somatotropin) o prolactin - to stimulate milk production after giving birth o ACTH (adrenocorticotropic hormone) - to stimulate the adrenal glands o TSH (thyroid-stimulating hormone) - to stimulate the thyroid gland o FSH (follicle-stimulating hormone) - to stimulate the ovaries and testes o LH (luteinizing hormone) - to stimulate the ovaries or testes o intermediate lobe: o melanocyte-stimulating hormone - to control skin pigmentation o posterior lobe: o ADH (antidiuretic hormone) - to increase absorption of water into the blood by the kidneys o oxytocin - to contract the uterus during childbirth and stimulate milk production
    22. 22. Taradi 22interactive physiology hypophysis PatientPatient o Patient o Continued
    23. 23. Taradi 23interactive physiology hypophysis Growth Hormone (Somatotropic Hormone)Growth Hormone (Somatotropic Hormone) o GH causes growth of almost all tissues. o GH stimulates cartlage and bone growth. o GH has multiple metabolic effect: o increased rate of protein synthesis in most cells and decrease catabolism o increased mobilization of fatty acids from adipose tissue o increased use of the fatty acids for energy o decreased rate of glucose utilization o GH is secreted in pulsatile pattern during whole life.
    24. 24. Taradi 24interactive physiology hypophysis The 2-D Structure of Human GHThe 2-D Structure of Human GH o Growth hormone, also known as somatotropin, is a protein hormone of about 190 amino acids that is synthesized and secreted by cells called somatotrophs in the anterior pituitary.
    25. 25. Taradi 25interactive physiology hypophysis GH binding to the MembraneGH binding to the Membrane o GH circulates in blood bound to a specific binding protein, termed GHBP. o Signaling and transduction only occur when adjacent receptors bind the two specific binding sites on the growth hormone moiety to form a dimmer.
    26. 26. Taradi 26interactive physiology hypophysis Somatomedin (GH/IGF-I) AxisSomatomedin (GH/IGF-I) Axis o GH causes the liver to form several small proteins called sopmatomedins. o The most important is somatomedin C (insulin- like growth factor-I) o The growth hormone/ insulin-like growth factor-I axis o Short duration of action of GH o Prolongated action of IGF-I
    27. 27. Taradi 27interactive physiology hypophysis GH Stimulates GrowthGH Stimulates Growth o Increased deposit of proteins in almost all tissue. o Increased deposit of proteins by chondrocytic and osteogenic cells. o GH converts chondrocytes into osteoblasts. o GH strongly stimulates the osteoblasts. o The thicknes of the epiphyseal cartilages and the bone increases.
    28. 28. Taradi 28interactive physiology hypophysis Metabolic Effects of GHMetabolic Effects of GH o PROTEINS o increased rate of protein synthesis in most cells o enhancement of amino acid transport into cells o enhancemant of RNA translation o stimulation of transcription of DNA o decreased catabolism of protein and amino acids o FAT o increased mobilization of fatty acids from adipose tissue o increased use of the fatty acids for energy o ketogenic effect o CARBOHYDRATE o decreased rate of glucoce utilization o increased glucose production by the liver o increased insulin secretion o diabetogenic effects
    29. 29. Taradi 29interactive physiology hypophysis Factors thatFactors that SStimulate andtimulate and SSuppressuppress GHGH SSecretionecretion o Two hypothalamic hormones regulate GH secretion: o Growth Hormone Releasing Hormone (GHRH) with a stimulatory action at the level of gene transcription o Somatostatin (SST) with an inhibitory effect on the GH secretion from the pituitary gland.
    30. 30. Taradi 30interactive physiology hypophysis Regulation of GH SecretionRegulation of GH Secretion o Stimulators o GHRH o starvations o hypoglycemia o exercise o stress o deep sleep o ghrelin o Inhibitors o somatostatin o obesity o aging o hyperglycemia o somatomedins
    31. 31. Taradi 31interactive physiology hypophysis Abnormalities of GH SecretionAbnormalities of GH Secretion o Hypersecretion o Gigantism (before adolescence) o Acromegaly (after adolescence) o Hyposecretion o Dwarfism (before adolescence) o Panhypopituitarism in the adults (after adolescence)
    32. 32. Taradi 32interactive physiology hypophysis GigantismGigantism o Overproduction of GH during adolescence result in gigantism.
    33. 33. Taradi 33interactive physiology hypophysis Acromegalic PatientAcromegalic Patient o The disease occurs as a result of excessive secretion of GH after adolescence. o In more than 99% of cases this is due to a benign pituitary GH secreting adenoma.
    34. 34. Taradi 34interactive physiology hypophysis Posterior PituitaryPosterior Pituitary o Magnocellular neurons of the hypothalamus secrete neurohormones o ADH (vasopressin) o Oxytocin o These peptide hormones are released into the blood in the posterior pituitary.
    35. 35. Taradi 35interactive physiology hypophysis Hypothalamic Control of PosteriorHypothalamic Control of Posterior PituitaryPituitary o Hypothalamus neuron cell bodies produce: o ADH: supraoptic nuclei. o Oxytocin: paraventricular nuclei. o Transported along the hypothalamo- hypophyseal tract. o Stored in posterior pituitary. o Release controlled by neuroendocrine reflexes.
    36. 36. Taradi 36interactive physiology hypophysis Antidiuretic Hormone (Vasopressin)Antidiuretic Hormone (Vasopressin) o The single most important effect of ADH is to conserve body water by reducing the output of urine.
    37. 37. Taradi 37interactive physiology hypophysis Chemical StructureChemical Structure o Antidiuretic hormone, also known as vasopressin, is a nine amino acid peptide secreted from the posterior pituitary.
    38. 38. Taradi 38interactive physiology hypophysis Physiological Functions of ADHPhysiological Functions of ADH o ADH stimulates water reabsorbtion by stimulating insertion of "water channels" or aquaporins into the membranes of kidney tubules. o These channels transport solute-free water through tubular cells and back into blood, leading to a decrease in plasma osmolarity and an increase osmolarity of urine.
    39. 39. Taradi 39interactive physiology hypophysis Effects on the Vascular SystemEffects on the Vascular System o High concentrations of ADH cause widespread constriction of arterioles, which leads to increased arterial pressure. o In healthy humans, ADH has minimal pressor effects.
    40. 40. Taradi 40interactive physiology hypophysis Affect and regulation of ADHAffect and regulation of ADH o Reduced urine volumen o Water retention o Increased blood pressure
    41. 41. Taradi 41interactive physiology hypophysis Regulation of ADH ProductionRegulation of ADH Production o The most important variable regulating ADH secretion is plasma osmolarity, or the concentration of solutes in blood. o Osmolarity is sensed in the hypothalamus by neurons known as an osmoreceptors. o Those neurons, in turn, simulate secretion from the neurons that produce ADH.
    42. 42. Taradi 42interactive physiology hypophysis Diabetes InsipidusDiabetes Insipidus o The most common disease of man and animals related to ADH is diabetes insipidus: o Hypothalamic ("central") diabetes insipidus results from a deficiency in secretion of ADH. o Nephrogenic diabetes insipidus occurs when the kidney is unable to respond to ADH o The major sign of either type of diabetes insipidus is excessive urine production.
    43. 43. Taradi 43interactive physiology hypophysis OxytocinOxytocin o Oxytocin in a nine amino acid peptide that is synthesized in hypothalamic neurons and transported down axons of the posterior pituitary for secretion into blood.
    44. 44. Taradi 44interactive physiology hypophysis Physiologic Effects of OxytocinPhysiologic Effects of Oxytocin o Stimulation of uterine smooth muscle contraction at birth o Oxytocin is released during labor when the fetus stimulates the cervix, and it enhances contraction of uterine smooth muscle to facilitate parturition or birth.
    45. 45. Taradi 45interactive physiology hypophysis Physiologic Effects of OxytocinPhysiologic Effects of Oxytocin o Stimulation of milk letdown (milk ejection) o Establishment of maternal behavior o Facilitation of sperm transport within the male and female reproductive system
    46. 46. Taradi 46interactive physiology hypophysis Control of Oxytocin SecretionControl of Oxytocin Secretion o The most important stimulus for release of hypothalamic oxytocin is initiated by physical stimulation of the nipples or teats. o A number of factors can inhibit oxytocin release, among them acute stress.
    47. 47. Taradi 47interactive physiology hypophysis PatientPatient o SIGNS o 50-year-old man complaining of impotence o shoe size had increased o his friends have remarked on changes in appearance (the cranium, nose supraorbital ridges, lower jawbone, hunched back o the hands develop a size almost twice normal o his dental plate had to be altered three times in 5 years. o he was shaving less frequently
    48. 48. Taradi 48interactive physiology hypophysis PhysicalPhysical and laboratoryand laboratory examination:examination: o the hands and feet were enlarged o the liver, tongue, kidneys and other soft tissue were enlarged o visual fields showed a loss of both lateral (temporal) fields o the plasma level glucose was 10 mEq/L o magnetic resonance imaging showed a large pituitary mass protruded upward from sella turcica o increased growth hormone level
    49. 49. Taradi 49interactive physiology hypophysis Questions:Questions: o Why did physician measure the growth hormone? o The changes in patient’s appearance and shoe size strongly suggest an excess of GH.
    50. 50. Taradi 50interactive physiology hypophysis Questions:Questions: o What is the cause of hypersecretion of GH? o Usually a benign acidophilic tumor of pituitary somatotrophs.
    51. 51. Taradi 51interactive physiology hypophysis Questions:Questions: o What is the name of disease? o Acromegaly
    52. 52. Taradi 52interactive physiology hypophysis Questions:Questions: o What has caused the changes in patient’s feet, hands, liver and facial features? o GH via somatomedin stimulated proliferation of chondrocytes, osteoblasts and connective tissue. The visceral organs growth is also stimulated.
    53. 53. Taradi 53interactive physiology hypophysis Questions:Questions: o The concentration of what peptide is certainly elevated in patient’s plasma? o GH stimulates the synthesis of a peptide mediator called somatomedin in the liver.
    54. 54. Taradi 54interactive physiology hypophysis Questions:Questions: o Way is the fasting plasma glucose level elevated? o GH is an insulin antagonistic hormone that inhibits insulin-stimulated glucose uptake by muscle, fat and the liver. GH decrease carbohydrate utilization.
    55. 55. Taradi 55interactive physiology hypophysis Questions:Questions: o What changes in the plasma insulin level would you expect to find? o Plasma insulin levels will be elevated in response to high glucose levels. GH’s effects are called diabetogenic.
    56. 56. Taradi 56interactive physiology hypophysis Questions:Questions: o What changes do you expect in blood level of fatty acids? o GH increase the blood concentration of fatty acids because release from adipose tissue. GH enhances fat utilization for energy. Excessive amount of GH causes ketosis, fatty liver and atherosclerosis.
    57. 57. Taradi 57interactive physiology hypophysis Questions:Questions: o What is the most likely cause of patient’s impotence? o A low plasma testosterone level caused by o direct destruction of gonadotropin-producing cell by tumour pressure (decrease of LH and FSH), or o ablation of hypophyseal stalk (decrease of GnRH) o secretion of prolactin by tumours which inhibit GnRH release
    58. 58. Taradi 58interactive physiology hypophysis Questions:Questions: o What has caused the impairment of visual fields? o Pressure from tumor on optic nerves cross causes bitemporal hemyanopsia.
    59. 59. Taradi 59interactive physiology hypophysis Questions:Questions: o What is the best therapy? o microsurgical removal of tumour o local irradiation o therapy with somatostatin which can reduce the elevated GH by inhibiting receptors on tumors cells.
    60. 60. Taradi 60interactive physiology hypophysis Questions:Questions: o If the tmour mass were removed surgically, what physical changes would you expect? o The swelling of soft tissue would resolve promptly, but the bone changes would resolve very slowly. o Also removal the anterior pytuitary gland would cause permanent deficiencies in TSH, ACTH, FSH, LH and prolactin. Replacement therapy with thyroxine and cortisol would be necessary.
    61. 61. Taradi 61interactive physiology hypophysis Questions:Questions: o Would be aldosteron needed? o No o Would be prolactin needed? o No, there are no known consequences of prolactin deficiency in males.
    62. 62. Taradi 62interactive physiology hypophysis Questions:Questions: o How about sexual hormons? o If the patient wished only to restore sexual potency, he would require only testosterone replacement. o If he still whished to father of child the treatment with GnRH, or LH and FSH can be rarely effective.
    63. 63. Taradi 63interactive physiology hypophysis Questions:Questions: o Would be ADH needed? o Removal of posterior pituitary gland would not ordinarily cause ADH deficiency and diabetes insipidus. ADH is formed primarily in the supraoptic nuclei.
    64. 64. Taradi 64interactive physiology hypophysis QuestionsQuestions??

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