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Pituitary Gland
Hormones and their physiological effects
pituitary gland (hypophysis)
 Often
called the "Master Gland," the
pituitary gland lies in the sella turcica at
the base of the skull. It is a small endocrine
organ that is controlled by the
hypothalamus, and directs other organs and
endocrine glands to suppress or induce
hormone production.
Structure of the pituitary gland
 The
anterior lobe (or adenohypophysis)
 The
intermediate / middle lobe
 The
posterior lobe (or neurohypophysis)
Intermediate Lobe
anterior pituitary
 Human
growth hormone (HGH)
 Thyroid-stimulating
hormone (TSH)
 Adrenocorticotropic
hormone (ACTH)
 Prolactin
(PRL)
 Luteinizing
hormone (LH)
 Follicle-stimulating
hormone (FSH)
Intermediate pituitary
 Melanocyte
stimulating Hormone (MSH)
posterior pituitary
 Antidiuretic
 Oxytocin
hormone (ADH)
Anterior Pituitary
Hormones
Growth Hormone (GH):

GH stimulates overall protein synthesis with an associated
retention of phosphorous probably by increasing tubular
reabsorption.

GH increases DNA & RNA synthesis

It increases the synthesis of collagen

GH brings about “Lipolysis” in a mild way by mobilizing
fatty acids from adipose tissue by activating the hormone
sensitive “triacylglycerol lipase”.

Hypersecretion of GH can result in hyperglycemia, poor
sugar tolerance and glycosuria.
Abnormalities of GH

Panhypopitutarism: It is due to decreased secretion of all
the anterior pituitary gland hormones. It may be
congenital (or) ii may occur suddenly during the life of the
individual.

Dwarfism: It is due to deficiency of anterior pituitary
gland secretion during childhood.

Levi-lorain dwarfism: It is due to hereditary inability to
form somatomedin C, but the rate of GH secretion.

Acromegalay: It is due to increased secretion of GH.
AdrenoCorticoTrophic hormone (ACTH):

ACTH increases the synthesis of corticosteroids by the adrenal
cortex and also stimulates their release from the gland.

ACTH is found to increase the transfer of cholesterol from
plasma lipoproteins into the fasciculata cells.

The ACTH induces rise in cAMP, brings about phosphoryl and
activation of “Choleseryl esterase”

the enzyme action ultimately makes a large pool of free
cholesterol.

It activates the rate-limiting enzyme for conversion of
cholesterol to pregnenolone (Cholesterol desmolase) .

It activates dehydrogenases of HMP to increase the
concentration of NADPH required for hydroxylation.

It activates “Hormone-sensitive lipase”, which is involved in
lipolysis which increases the level of free fatty acids.
Abnormalities of ACTH

Cushing’s disease: Over secretion of ACTH leads to
cushing’s disease, because of tumor (or) hyperplasia of βcells of the anterior pituitary gland lobe. This leads to
hypersecretion of corticosteroids specially
glucocortucoids. This produces symptoms like
hyperglycemia, glycosuria, muscle wasting, atrophy of
skin, high urinary negative nitrogen balance. Abnormal
retention of fats giving moon shape face appearance,
retention of Na + and water and hypertension.
Leutinizing Hormone:

In females:

It causes the final maturation of graffian follicles and
stimulates ovulation.

Stimulates secretion of estrogen by the THECA and
Grannulosa cells.

It helps in the formation and development of corpus lutem
for leutinization of cells.

In the ovary it can stimulate the non-germinal elements,
which contain the interstitial cells to produce the
androgenes, androstenedione, DHEA and testosterone.
Follicle Stimulating Hormone (FSH):

It brings about its action by specific receptor binding and
cAMP
In Females:

It promotes follicular growth

Prepares the graffian follicle for the action of LH.

Enhances the elease of estrogen induces by LH.

In Males:

It stimulates seminal tubular and testicular growth.

Plays an important role in maturation of spermatozoa.
Thyroid Stimulating Hormone (TSH):

It stimulates the activity of thyroid gland and
enhances the rate of certain reactions, such as,

Removal of iodine form blood by thyroid.

Conversion of iodide to thyroid hormones.

Release of hormonal iodide from thyroid.
Intermediate pituitary
Hormones
Melanocyte stimulating Hormone (MSH):
 MSH
darkens the skin and is involved in skin
pigmentation by deposition of mammalian
by melanocytes.
 Abnormality:
Addison’s disease: MSH is in
excess, which increases the synthesis of
melanin resulting in brown pigmentation of
skin. Such a condition occurs in this
disease.
Posterior Pituitary Hormones

Antidiuresis:
Vasopressin causes “Antidiuresis”. It increases the
permeability of the collecting ducts and tubules to water
and allows most of the water to be reabsorbed as the
tubular fluid passes through these ducts, there by
conserving water in the body and producing very
concentrated urine.

Urea-retention effect:

Permeability of meduallry collecting dusts to urea is
increases by vasopressin. This leads to retention of urea
and subsequently contributes to hypertonicity of the
medullary intersitium.

Pressor effect: It stimulates the contraction of smooth
muscles and thus causes vasoconstiction by increasing
cytosolic Ca +2 concentration.

Glycogenolytic effect: By increasing intracellular Ca +2
concentration, it causes glycogenolysis.

Abnormality:
Deficiency of ADH leads to “Diabetes insipidus”, it
is characterized by excretion of large volumes of
dilute urine. Excess secretion of ADH often results
from ectopic production of ADH by malignant
tumors, referred to as the “Syndrome of
Inappropriate secretion of ADH” (SIADH). There is
hypotonic expansion of extracellular volume, with
hyponatremia.
Oxytocin:
 Function:
Oxytocin mainly causes smooth
muscle contraction.
 a)
Effect on the uterus and on birth:
Oxytocin causes the contraction of the
pregnant uterus especially toward the end
of gestation and is partially responsible for
effecting birth.
 b)
Effect of oxytocin on milk ejection:
Oxytocin has an effect on the mammary
gland. Suckling generates a neurogenic
reflex, which stimulates the production of
oxytocin of oxytocin. It causes contraction
of the myoepithelial called expelling the
milk into milk ducts from the acinii.
THE END