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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