PITUITARY GLAND

ANTERIOR PITUITARY HORMONES

POSTERIOR PITUITARY HORMONES

GLYCOPROTEIN FAMILY

  • thyroid stimulating hormone
  • luteinizing hormone
  • follicular stimulating hormone

GROWTH HORMONE FAMILY

  • growth hormone (GH)
  • prolactin (PRL)

PRO-OPIOMELANOCORTIN PEPTIDES

  • adrenocorticotrophic hormone ACTH
  • melanocyte stimulating hormone MSH
  • beta - lipotropin BLPH
  • beta - endorphin

antidiuretic hormone ADH

oxytocin

ACTIONS OF GROWTH HORMONE

METABOLIC ACTIONS

GROWTH PROMOTING ACTIONS - GH promotes linear growth of an individual by its effects on the bone, cartilage and other connective tissues

EFFECT ON LACTATION - GH enhances milk production in lactating animals. Gh acts like prolactin - prolactin like effect of growth hormone

effect on cartilage - GH stimulates proliferation of chondrocytes present in epiphyseal end plates of long bones

effect on bone

  • GH stimulates osteoblastic activity - converts cartilage into bone.
  • this process continues up to adolescence till there is fusion of epiphyseal plate with shaft of bone.
  • the bone mas also increases in this period

effect on fat metabolism - GH promotes lipolysis in adipose tissue and then increases fat utilization for energy

effect on protein metabolism- GH has anabolic effects on protein metabolism. it promotes protein deposition in tissue by following effects

effect on carbohydrate metabolism - antagonist to insulin and produces hyperglycemia by following effects on carb metabolism

effect on mineral metabolism - promotes bone mineralization in growing children. this effect is mediated through IGF-1 - causes +ve Ca, P, Mg balance

increase the rate of amino acid uptake into cells

increase protein synthesis in ribosomes

stimulates transcription

overall effect is positive nitrogen balance that leads to increase in body weight.

GH also decreases protein catabolism as well as rate of amino acid degradation

increase gluconeogenesis i.e., increases hepatic glucose output

decreases uptake as well as utilization of glucose by the tissues for energy production

inhibits glycolysis and thus glycogen stores tend to increase

promotes renal absorption of Ca, P, Na and retention of Na, K, Cl in body

ACROMEGALY

INTRODUCTION

  • means enlargement of acral (peripheral) parts of the body
  • due to hypersecretion of GH after fusion of epiphysis

ETIOLOGY

  • due to tumor of somatotrophs of anterior pituitary
  • tumor of somatotrophs is associated with proliferation of lactotrophs so PRL secretion is also increased

also occurs due to extra pituitary causes like inc. hypothalamic secretion of GRH

FEATURES

  • enlargement of acral parts of the body esp. hands and feet
  • prognathism (lower jaw protrusion)
  • acromegalic face (overgrowth of malar, frontal and facial bones,)
  • inc in amount of body hair
  • osteoarthritis - due to skeletal changes
  • glucose intolerance
  • hirsutism
  • gynecomastia & lactation
  • visual field changes (bitemporal hemianopia)
  • kyphosis due to improper vertebral growth
  • inc sympathetic activity causes hypertension asd sweating

MANAGEMENT - diagnosis by typical clinical presentation, demonstration of pituitary tumor by CT scan or MRI, demonstration of high plasma GH level. surgical removal of tumor is the best option to cure the disease

bones enlarge in width cannot grow in length as epiphyses are fused

visual defects - pituitary tumor enlarges sella turcica and compresses on optic chiasma. This also causes headache

visceromegaly- inc size and function of viscera

FUNCTIONS OF OXYTOCIN

APPLIED PHYSIOLOGY

milk ejection reflex (example of neurohormonal reflex)

parturition reflex also neurohormonal

prevent excessive post partum haemorrhage

suckling of nipple by the baby

nipple stimulated

afferent neural impulses - nipple to spinal cord to spinothalamic tract to brainstem

paraventricular nucleus of hypothalamus

fibres stimulate oxytocin secreting magnocellular neurons of hypothalamus

hypothalamo-pituitary axis

oxytocin released from post pit.

enters circulation

causes contraction of myoepithelial cells of milk laden alveoli of mammary glands

causes contraction of non preg uterus to facilitate sperm motility

secretion inc in males during orgasm

degeneration of corpus luteum at end of menst cycle

toward term

oxytocin secretion gradually increases

reaches peak just before parturition

uterus contracts vigorously leading to expulsion of fetus

in uterine muscle

inc in no. of oxytocin receptors

induce labor

FUNCTIONS OF ADH

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