MODULE 2: THE PITUITARY GLAND Flashcards
The Greek origin of the word pituitary is ________, meaning to spit?
ptuo
Latin origin of the word pituitary
is _________, meaning mucus.
pituita
The pituitary gland once was considered the what?
“Master gland of the body”
This title was bestowed on it because the hormones it secreted affected almost all other endocrine glands of the body and because the pituitary gland seemed to be at the physical and functional apex of the endocrine system.
“Master gland of the body”
is now known to be controlled by chemical and electrochemical messengers emanating from the brain and other organs and glands
pituitary gland
is a major controlling participant in the endocrine system
pituitary gland
produces only closely related steroids
adrenal cortex
produces many polypeptide hormones ranging from small peptides to large full-fledged proteins, like luteinizing hormone (LH), follicle-stimulating hormone
(FSH), prolactin, and growth hormone, each consisting of approximately 200 amino acids.
pituitaary gland
large full-fledged proteins produced by the pituitary gland
Luteinizing hormone (LH),
Follicle-stimulating hormone
(FSH)
Prolactin
Growth hormone
each consisting of approximately 200 amino acids
The pituitary gland is also called
hypophysis
pituitary gland = hypophysis
Greek: ?
meaning: ?
hypo = under
physis = growth
It is found ventral to the brain in a dorsal concavity of the sphenoid bone called the
sella turcica or hypophyseal fossa.
pituitary gland
dorsal concavity of the sphenoid bone called
sella turcica or hypophyseal fossa.
surrounds the pituitary gland bilaterally and ventrally
sphenoid bone
It is covered by the dura
mater
sphenoid bone
a tough fibrous membrane lining the sella turcica and forming the outer layer of the brain
dura mater
rises dorsally from the pituitary to connect with the hypothalamus
pituitary stalk or infundibulum
forms the floor of the third ventricle of the brain and is the site where hypothalamic-releasing hormones enter the primary plexus of the hypophyseal portal system
hypothalamus
Anatomical subdivisions of the pituitary gland:
- Adenohypophysis (anterior pituitary)
- Neurohypophysis (posterior pituitary)
posterior pituitary also known as
Neurohypophysis
anterior pituitary also known as
Adenohypophysis
Three parts of the adenohypophysis:
- the pars distalis
- the pars tuberalis
- the pars intermedia
part of the anterior pituitary which is the largest part of the adenohypophysis and contains five
populations of cells
pars distalis
five populations of cells of Pars Distalis
(i) thyrotropes
(ii) gonadotropes
(iii) lactotropes
(iv) corticotropes
(v) somatotropes
which secrete the “tropic” hormones that regulate function of other endocrine glands
corticotropes
corticotropes, which secrete the “_______” hormones that regulate function of other endocrine glands
tropic hormones
which regulate other nonendocrine organs and tissues
somatotropes
Tropic Hormones
- thyrotropin or thyroid-stimulating hormone (TSH)
- luteinizing hormone (LH)
- follicle-stimulating hormone (FSH)
- prolactin, adrenocorticotropin (ACTH)
- growth hormone (GH) or somatotropin (STH)
Growth hormone (GH) also known as?
somatotropin (STH)
is an upward extension of the adenohypophysis and is attached to the infundibulum
pars tuberalis
forms the junction between the pars distalis and pars nervosa and is the source of melanocyte-stimulating hormone (MSH)
pars intermedia
pars intermedia forms the junction between these two parts of adenohypophysis or (anterior pituitary)
pars distalis and pars nervosa
pars intermedia is the source of this hormone
melanocyte-stimulating hormone (MSH)
particularly important in amphibians in regulating skin
pigmentation
elanocyte-stimulating hormone (MSH)
ACTH of these animals are produced by the pars intermedia
cattle, pigs, and rats
In cattle, pigs, and rats, ACTH produced by the _________ is cleaved into α- MSH and
corticotropin-like intermediate lobe peptide (CLIP)
pars intermedia
The pars intermedia of these animals is a significant source of ACTH, and tumors of the pars
intermedia can lead to spontaneous hyperadrenocorticism in these species.
dog and horse
tumors of the pars
intermedia can lead to _______in dog and horse
spontaneous hyperadrenocorticism
The ____________ of the dog and horse is a significant source of ACTH, and tumors of this part of Adenohypophysis (anterior pituitary) can lead to spontaneous hyperadrenocorticism in these species.
pars intermedia
Two parts of the neurohypophysis (posterior pituitary):
- infundibulum or pituitary stalk
- pars nervosa or posterior or neural lobe
Hormones produced in the hypothalamus and stored in and
released from the neurohypophysis
nonapeptides
Hormones produced in the hypothalamus and stored in and
released from the neurohypophysis are nonapeptides and include:
(OLAA)
Oxytocin
Lysine vasopressin
Arginine vasopressin
Arginine vasotocin
The pituitary gland receives
both of these type of blood.
arterial blood and venous blood
supplying blood to the anterior pituitary gland
Hypophyseal portal system
are two paired arteries originating from the internal carotid arteries
arterial sources
two paired arteries of arterial sources
Superior hypophyseal arteries Inferior hypophyseal arteries
it enters the adenohypophysis from two capillary beds
Venous blood
This unique circulatory architecture constitutes the ________ and forms the endocrine link of the hypothalamus, higher brain centers, and neurohypophysis with the adenohypophysis.
hypophyseal portal system (
High concentrations of hypothalamic hormones affecting adeno-hypophyseal function are
present in this type of blood.
portal blood
How much % of the blood supply for the adenohypophysis comes from the portal circulation emphasizes its functional significance.
80 to 90%
Blood for the neurohypophysis comes from?
inferior hypophyseal arteries
Venous blood leaves the pituitary gland through _________ to enter the internal jugular veins.
venous sinuses
receives no direct innervation, except for a few sympathetic fibers that enter along the blood vessels.
adenohypophysis
possesses a rich supply of nerves.
neurohypophysis
Fibers originating from the paraventricular, supraoptic, and other hypothalamic nuclei enter
the neurohypophysis via the
infundibulum
Fibers originating from the paraventricular, supraoptic, and other hypothalamic nuclei contain?
oxytocin, vasopressin, or vasotocin in nonmammalian species
Fibers originating from the paraventricular, supraoptic, and other hypothalamic nuclei also contain their respective carrier proteins called
neurophysins
it delivers blood to a capillary network in the upper infundibulum
superior Hypophyseal Artery
deliver blood containing regulatory hormones to the capillary network in the anterior lobe of the pituitary
Portal Vessels
it delivers blood to the posterior lobe of the pituitary gland
Inferior Hypophyseal Artery
carry blood containing the pituitary hormones to the cardiovascular system for delivery to the rest of the body
Hypophyseal Veins
secrete releasing hormones and inhibiting hormones
Hypothalamic Neurons
stimulate or inhibit the secretion of anterior pituitary hormones
Releasing hormones
develop from different embryologic structures
Adenohypophysis and Neurohypophysis
including the infundibulum and the neural lobe, is a specialized extension from the wall of the diencephalon of the developing brain
neurohypophysis
arises from an evagination of the ectodermal roof of the oropharynx (i.e., a mouth cavity) commonly
called Rathke’s pouch.
adenohypophysis
adenohypophysis commonly
called
Rathke’s pouch.
enlarges quickly, flattens against the infundibular extension from the brain, and encircles it
Rathke’s pouch
The anterior wall of Rathke’s pouch thickens to become what?
pars distalis
the back wall of Rathke’s pouch remains thin and becomes what?
pars intermedia
forms from the craniopharyngeal duct near the point that fuses with the pars nervosa
pars intermedia
pars intermedia forms from the _________ near the point that fuses with the pars
nervosa
craniopharyngeal duct
This embryonic development results in a total neurologic connection of the neurohypophysis with
the hypothalamus but in an almost total lack of innervation to the adenohypophysis.
pars intermedia
The adenohypophysis, consisting of the pars
distalis, pars intermedia (solid black), and pars tuberalis, arises from evagination of the ____________ commonly called Rathke’s pouch
ectodermal roof of the
oropharynx
Every hormone produced by the adenohypophysis is regulated by at least one hormone synthesized in
hypothalamic nuclei and released into the blood of the hypophyseal portal system to be transported to the pars distalis.
Hypothalamic hypophysiotropic substances that stimulate pituitary function originally were called ____________ after the initial designation of corticotropin-releasing factor (CRF).
releasing factors
corticotropin-releasing factor (CRF) and other
releasing factors are considered what?
true hormones
corticotropin-releasing factor (CRF) and other
releasing factors are considered true hormones, secreted for ___________.
hemocrine communication
All hypophysiotropic hormones except __________ are peptides.
dopamine
prolactin release-inhibiting hormone
dopamine
The synthetic stimulatory hypophysiotropic hormones are:
(i) Thyrotropin-releasing hormone (TRH)
(ii) Gonadotropin-releasing hormone (GnRH)
(iii) Corticotropin-releasing hormone (CRH)
(iv) Growth hormone-releasing hormone (GHRH)
cells in the supraoptic and paraventricular hypothalamic nuclei secrete what hormones?
vasopressin and oxytocin
it secrete vasopressin and
oxytocin
cells in the supraoptic and paraventricular hypothalamic nuclei
also is involved in the control of secretion of ACTH
Arginine vasopressin (AVP)
Arginine vasopressin (AVP) also is involved in the control of secretion of this hormone.
ACTH
Now, it is recognized that some pituitary hormones also are under control of inhibiting hormones
secreted by the hypothalamus.
are regulated by both releasing and inhibitory hormones
Prolactin
growth hormone
TSH
not only stimulates release of TSH, but it also induces the release of prolactin and growth hormone
TRH
TRH not only stimulates release of TSH, but it also induces the release of these hormone.
prolactin and growth
hormone
stimulates release of both LH and FSH
Gonadotropin-releasing hormone
Gonadotropin-releasing hormone stimulates release of both of these hormones.
LH and FSH
do more than stimulate release of pituitary hormones. They also regulate pituitary
cell differentiation, proliferation, and hormone synthesis.
Releasing hormones
is a 39-amino acid peptide derived from a much larger precursor called proopiomelanocortin (POMC
Adrenocorticotropin
Adrenocorticotropin is a 39-amino acid peptide derived from a much larger precursor called
proopiomelanocortin (POMC)
The first ____ amino acids of ACTH have the full biologic activity of the whole molecule
18 amino acids
first _____ amino acids are the same in all species of animal
24 amino acids
Other peptides with hormonal activity derived from POMC include:
β-endorphin
β-lipotropin
α-melanocyte-stimulating hormone (α-MSH)
may act to regulate prolactin
secretion
Beta-endorphin and β-lipotropin
Secretion of ACTH is regulated by hypothalamic _____________
corticotropin-releasing hormone (CRH)
Arginine vasopressin (AVP)
is a weak regulator of ACTH
Arginine vasopressin (AVP)
it acts synergistically with CRH to stimulate
secretion of ACTH
Arginine vasopressin (AVP)
second messenger
cyclic AMP
induces the immediate release of ACTH and transcription of the gene for POMC.
Cyclic AMP
from the adrenal cortex feeds back negatively to
regulate CRH and ACT secretion
cortisol or corticosterone
it regulates CRH secretion via short-loop feedback to the hypothalamus
ACTH
stimulates the release of ACTH in a pulsatile manner
CRH
a circadian rhythm with the highest pulse frequency of ACTH release in blood occurs just before and during the hour after awakening in the
morning.
even minor, is a potent stimulus for secretion of ACTH and cortisol.
Hemorrhage
internal and external stress stimuli increase ACTH and cortisol secretion in prenatal and postnatal domestic animals.
hypoxemia
hypotension
hypoglycemia
ambient temperature
surgery
trauma
pain
stimulates the cortex of the adrenal gland to secrete the steroid hormone cortisol
in most mammals or corticosterone in rodents and lagomorphs.
Adrenocorticotropin
Adrenocorticotropin stimulates the cortex of the adrenal gland to secrete the steroid hormone _______
in most mammals or _______ in rodents and lagomorphs.
cortisol
corticosterone
In birds, ACTH stimulates secretion of
androgens and mineralocorticoids
In mammals, the adrenal secretion of mineralocorticoids is not under the control of ACTH.
it acts on the two inner zones (zona fasciculata and reticularis) of the
adrenal cortex to increase cortisol or corticosterone secretion.
Adrenocorticotropin
two inner zones of the
adrenal cortex
zona fasciculata and reticularis
The adrenal cortex responds to ACTH _________, by hypertrophy of cells in the zonae fasciculata and reticularis
morphologically
The adrenal cortex responds to ACTH __________, by increased production of glucocorticoids.
functionally
Synthesis of adrenocortical steroids requires:
(a) cleavage of the side chain from cholesterol to form a steroid called pregnenolone.
(b) various hydroxylation of pregnenolone
(c) oxidation of the 3β-hydroxyl to a 3-ketone
(d) a shift of the double bond from carbons 5 and 6 to carbon 4 and 5.
cleavage of the side chain from cholesterol to form a steroid called
pregnenolone
is usually the rate-limiting step in steroidogenesis.
Side-chain cleavage of cholesterol
Four major sources of cholesterol are available to the cell to meet its metabolic needs:
(i) Hydrolysis of intracellular cholesterol ester
(ii) de novo cholesterol synthesis
(iii) direct delivery into the cell by passive diffusion of monomolecular cholesterol
(iv) uptake of cholesterol associated with plasma lipoproteins
Uptake of lipoproteins by adrenal cells, conversion of a cholesterol ester to cholesterol, and side-chain
cleavage of cholesterol are all stimulated by?
ACTH
PITUITARY PROTEIN HORMONES
- Adrenocorticotropin
- Prolactin
- Growth Hormone
is a single-chain polypeptide hormone
Prolactin
Its structure is similar in many species with only a
few amino acid substitutions.
Prolactin
Prolactin is produced by widely dispersed pituitary gland cells called
lactotropes or mammotropes
named because of the hormone’s indispensable role in lactation
lactotropes or mammotropes
is prevalent in all vertebrates from fish to humans.
Prolactin
It plays a major role in many reproductive and nonreproductive events including:
1. regulation of
metamorphosis in amphibians
2. osmoregulation in teleost fish
3. proliferative effects on male accessory organs
4. regulation of parental behavior in several species
5. stimulation of the blood patch in the sparrow
6. stimulation of crop milk formation in pigeons
Prolactin
In rodents, this hormone is important in maintaining structure and function of corpora lutea of the female.
prolactin
in some old and new literature, prolactin is called
luteotropic hormone (LTH)
In addition, prolactin
stimulates development of receptors for LH on Leydig cells. Hence, prolactin indirectly stimulates secretion of what hormone?
testosterone
is the most versatile pituitary hormone as to function and species distribution
prolactin
its role in differentiation and maintenance of the mammary gland and secretion of milk are of primary importance
prolactin
The stimulus for let-down of milk is provided by?
suckling
are carried to the brain and to secretory neurons in the hypothalamus that release
hypophysiotropic hormones.
Neurogenic impulses
Neurogenic impulses are carried to the brain and to secretory neurons in the hypothalamus that release
these hormones.
hypophysiotropic hormones
In the pituitary gland, prolactin secretion is stimulated or inhibited by these hormones.
hypophysiotropic hormones
is under inhibitory control by dopamine
prolactin
prolactin is under inhibitory control by
dopamine
prolactin is secreted by the
hypothalamus
Surgical disconnection of the pituitary gland
hypophysectomy
Surgical disconnection of the pituitary gland (hypophysectomy) from the hypothalamus causes severe
reduction in concentration of most pituitary hormones in blood because of removal of hypothalamic-releasing
hormones on the gland.
initiates a prolonged tonic increase in prolactin
secretion
pituitary stalk transection
produces a significant elevation in prolactin
concentrations in blood.
posterior lobectomy of male rats
Low basal metabolic rate due to Hormone Deficiency in
TSH then thyroxin
Lack of libido in male
Anestrus in female
Ovulation failure in female
Failure to develop ova
Lack of secondary sex characteristics
Failure of function of accessory sex organs
due to Hormone Deficiency in
Gonadotropins (FSH and LH); then gonadal hormones
(testosterone or estrogen)
Gonadotropins
FSH and LH
gonadal hormones
testosterone or estrogen
Steatogenesis and degeneration of seminiferous
tubules of cockerel similar to end of breeding season of wild birds due to Hormone Deficiency in
Gonadotropins; then testosterone
Atrophy of adrenal cortex due to Hormone Deficiency in
ACTH
Cessation of growth due to Hormone Deficiency in
Somatotropin (STH) plus others (TSH, ACTH)
Somatotropin
STH
General depression of metabolism of fat,
carbohydrates, and protein due to Hormone Deficiency in
Adrenal steroids, STH, TSH, ACTH, gonadotropins
Cessation of lactation due to Hormone Deficiency in
Prolactin and STH; others like ACTH and TSH to lesser
degree
prolactin is released in a what manner
pulsatile manner
require constant inhibition by dopamine to keep prolactin secretion under control
pituitary lactotropes
Other prolactin-inhibiting factors
γ-aminobutyric acid and GnRH-associated peptide
Naturally occurring compounds that release prolactin includes:
TRH
vasoactive intestinal peptide
(VIP)serotonin
β-endorphin
somatostatin
gastrin
GnRH
vasopressin
oxytocin
angiotensin II
so-called because it is produced by cells of the small intestine and the nervous system and because it is a potent vasodilator
vasoactive intestinal peptide
(VIP)
have gained considerable credit as prolactin-releasing
hormones.
Thyrotropin-releasing a and VIP
Both are directly secreted into the hypophyseal portal blood and directly stimulate prolactin release from the pituitary gland.
Thyrotropin-releasing a and VIP
VIP is synthesized by the ______ and is present in lactotropes.
adenohypophysis
is synthesized by the adenohypophysis and is present in lactotropes.
vasoactive intestinal peptide (VIP)
VIP is a ____________ regulator of prolactin secretion.
hemocrine and autocrine
Prolactin is synthesized, processed, packaged, stored, and released by
lactotropes
affect both synthesis and release of prolactin.
Dopamine, TRH, and VIP
second messenger
(CIP)
cyclic AMP
ionized calcium
phosphoinositides
The primary mechanism of dopamine action
inhibition of cyclic AMP production
Intracellular second messengers for prolactin include
(PIP)
Polyamines (derivatives of the amino acid arginine)
Ionized calcium
Prostaglandin
The main site of action of prolactin
mammary gland
During pregnancy, the following hormones play roles in the development of the milk secretory apparatus.
insulin
cortisol
triiodothyronine (T3) estrogen
progesterone
growth hormone
prolactin
inhibit lactation during pregnancy
Estrogen and progesterone
after parturition, estrogen and progesterone concentrations in blood decrease rapidly, allowing this hormone to initiate lactation
prolactin
milk proteins, such as
casein
Growth hormone also known as
somatotropin
is a single-chain, non-glycosylated protein secreted by the pituitary
gland
Growth hormone or somatotropin
Growth hormone or somatotropin pulsatile secretion is regulated by a hypothalamic what?
growth hormone-releasing hormone (GHRH)
growth hormone release-inhibiting factor (somatostatin or SRIF)
controls growth hormone synthesis and release by affecting transcription of mRNA
Growth hormone-releasing hormone
Growth hormone-releasing hormone intracellular second messenger
cyclic AMP
appears to reduce growth hormone secretion independently of GHRH and by blocking GHRH action.
Somatostatin
Secretion of GHRH
and SRIF are controlled by ____________ from higher brain centers.
neuropeptides and neurotransmitters
Growth hormone several major actions
metabolism, growth, and cellular differentiation
Growth hormone increases ________ in adipose cells, ________ and protein synthesis in liver and muscle
cells, and ________ in bone
lipolysis
glycogenolysis
chondrogenesis
It also interacts with membrane receptors of the liver to cause the release
of growth-stimulatory peptides called
somatomedins
are single-chain proteins that closely resemble proinsulin
Somatomedins
Other growth promoters are important participants in tissue growth and organ development.
IGF-1 and IGF-2
Insulin-like growth factor-1, previously known as
somatomedin C
is an important mediator of growth hormone action and is produced by many cells, particularly those of the liver.
Insulin-like growth factor-1 (somatomedin C)
Blood concentration of IGF-1 are low in growth-hormone
deficiency that causes this disease
dwarfism
Blood concentration of IGF-1 are high in growth hormone excess that causes this disease
acromegaly
this breed of dogs has six times the mean plasma concentration of IGF-1 as Toy Poodles
Standard Poodles
is secreted by cells of the central nervous system and is involved mainly with fetal tissue development
Insulin-like growth factor-2
Concentrations of growth hormone in blood are high during rapid growth in several species
including
cattle, swine, and poultry
Growth of the long bones continues as long as this part do not close
epiphyseal growth
plates
Prolonged administration of growth hormone to dogs and several other species can induce
permanent hyperglycemia
Prolonged administration of growth hormone to dogs and several other species can induce a permanent
hyperglycemia; therefore, growth hormone is consider as
diabetogenic
The high blood glucose concentrations stimulate
the _____ cells of the pancreatic islets to produce insulin until they are eventually exhausted and undergo degeneration.
β cells
Growth hormone injected into growing and lactating
animals leads to improved nutrient utilization.
PITUITARY GLYCOPROTEIN HORMONES
- Thyrotropin
- Gonadotropins
Thyrotropin also known as
thyroid-ahormone (TSH)
appears to have only one physiological function-stimulation of the thyroid gland
Thyrotropin or thyroid-ahormone (TSH)
Bovine TSH is a
glycoprotein
T4
thyroxine
T3
triiodothyronine
causes a rapid reduction in transcription of mRNA by a direct action on its
nuclear receptor in the promoter regions of the α and β subunit genes
Triiodothyronine (T3)
Secretion of gonadotropins is regulated by
gonadal steroids and one peptide
gonadal steroids
estrogens, androgens, progesterone
Secretion of gonadotropins is regulated by gonadal steroids (i.e., ___________)
and at least one peptide (i.e., _________)
estrogens, androgens, progesterone
inhibin
is a glycoprotein with two polypeptide subunits synthesized by Sertoli cells of the testis, granulosa cells of the ovary, the
placenta, pituitary gonadotropes, and the brain
Inhibin
feeds back negatively on the hypothalamus and pituitary gland to specifically reduce secretion of FSH
Inhibin
intracellular messengers include
ionized calcium
inositol triphosphate (IP3)
diacylglycerol (DAG)
Gonadotropes are ______: They synthesize both LH and FSH. Because of this, there must be some mechanism whereby the two gonadotropins can be secreted individually.
bihormonal
Although males do not have corpora lutea, the currently accepted terminology is
luteinizing hormone (LH)
LH in male animals referred to as
interstitial cell-stimulating
hormone (ICSH)
HORMONES OF THE NEUROHYPOPHYSIS
Arginine Vasopressin and Oxytocin
antidiuretic hormone or ADH
Arginine vasopressin
are both nonapeptides with
a sulfhydryl bond between two cysteine residues at positions 1 and 6
Oxytocin and AVP
Pigs and other members of the suborder Suina produce this hormone, which contains lysine instead of arginine in position 8
lysine vasopressin
Oxytocin and AVP are released into the capillary blood in the pars nervosa
Cells of the hypothalamic nuclei initially synthesize this hormones, the products of single genes.
prohormones
During transport, these prohormones are cleaved to yield AVP or oxytocin, and their binding proteins,
called
neurophysins
The binding proteins for oxytocin is designated _________, and that for AVP is
designated _________
neurophysin I
neurophysin II
Release of the hormone and neurophysin from neurosecretory granules is initiated by _________
from sensory receptors monitoring the osmolarity of extracellular fluid.
electrical signals
Hydration of the body or injection of saline solution
into the blood going to the hypothalamus inhibits
release of __________, leading to resorption of less water
from the glomerular filtrate. Excess water is excreted
from the body as diluted urine.
AVP
_______of the body or injection of _________ into the blood going to the hypothalamus inhibits release of AVP, leading to resorption of less water from the glomerular filtrate. Excess water is excreted from the body as diluted urine.
Hydration & saline solution
______ or injection of _______into the hypothalamus stimulates release of AVP, causing increased water resorption in the distal tubules and decreased glomerular filtration, resulting
in less urine being produced.
Dehydration
hypertonic electrolyte
solutions
_______ is transported by blood to the kidney, where it binds to specific receptors in the distal part of the nephron and collecting ducts
Vasopressin
The major effect of AVP
to increase resorption of water from the glomerular filtrate
Like AVP, ______ is stored as
neurosecretory granules and is released from axonal terminals by calcium-dependent exocytosis.
oxytocin
The primary stimuli for
oxytocin release from storage sites in
the neurohypophysis are:
- distention of the reproductive tract,
particularly in the pregnant female - stimulation of the mammary gland by
the young - audiovisual contact with the offspring.
has specific effects on contraction of smooth muscle of the uterus and cells of the mammary
gland.
Oxytocin
oxytocin is used for
- inducing parturition in some species, or to increase uterine contraction at parturition
- for the treatment of retained placenta, metritis, and in some cases agalactia
absence of milk from the udder
agalactia
The mammalian anterior pituitary secretes six major hormones
prolactin
growth hormone
ACTH
LH
FSH
TSH
The mammalian anterior pituitary secretes six major hormones—prolactin, growth hormone, ACTH,
LH, FSH, and TSH. A deficiency of any of these can occur, such as
secondary hypothyroidism or secondary hypoadrenocorticism
secretion of all hormones from the anterior pituitary is
abnormally low or absent
panhypopituitarism
In young dogs, most of the clinical manifestations are associated with diminished
growth hormone secretion and dwarfism
panhypopituitarism
occurs most frequently in
German Shepherd dogs, but it also has been reported in a few breeds.
Juvenile panhypopituitarism
Juvenile panhypopituitarism occurs most frequently in
this breed of dogs, but it also has been reported in a few breeds.
German Shepherd
in German Shepherd usually is caused by a failure of Rathke’s pouch to differentiate into the hormone-secreting cells of the pars distalis
Pituitary dwarfism
Pituitary dwarfism in German Shepherd usually is caused by a failure of _______ to differentiate into the hormone-secreting cells of the pars distalis.
Rathke’s pouch
an α-adrenergic antagonist
clonidine
Basal growth hormone and IGF-1 concentration in plasma of dwarf dogs are greatly reduced, and
growth hormone concentration do not increase after injection of clonidine (an α-adrenergic antagonist), a standard dynamic test for growth hormone secretory capacity
Subsequently, slower growth rate relative to their littermates, the retention of puppy hair coats, and a lack of primary guard hairs (coarse hair covering the underfur) are indicative of this condition
dwarfism
develops gradually and
often progresses to complete alopecia except for the head and tufts
of hair on the legs. There is progressive hyperpigmentation of the
skin until it is uniformly brown-black over most of the body
bilaterally symmetrical alopecia
Clinical manifestations of growth hormone deficiency are worsened by concomitant secondary hypoadrenocorticism, hypothyroidism, and hypogonadism.
is a disease caused by excess growth hormone secretion
Acromegaly
Its clinical manifestations
include an overgrowth of connective tissue, increased growth of bone, coursing of facial features, and
enlargement of viscera
Acromegaly
The most common cause of Acromegaly in cats appears to be
growth hormone-secreting tumors of somatotropes
In dogs, the most common type of acromegaly is due to
________ induced by progesterone and progestogens
somatotropic hyperplasia
These neoplasms are
encountered most frequently in dogs and horses.
hyperadrenocorticism or excess cortisol secretion
They develop in adult to geriatric dogs and have been
reported in several breeds, but Boxers, Boston Terriers, and Dachshunds appear to have the highest incidence
derived from cells of the
pars distalis are the most common type of ACTH-secreting pituitary tumor in horses, ponies, and donkeys.
Adenomas
These tumors develop in older animals, with females
affected more frequently than males.
Adenomas
Affected animals often
develop a strikingly excessive growth of hair (hirsutism) because
of a failure of seasonal shedding of hair (
Adenomas
strikingly excessive growth of hair because of a failure of seasonal shedding of hair
hirsutism
Other clinical manifestations and sequelae associated with tumors of
the pars distalis are polyuria, polydipsia, hyperphagia, muscle weakness, laminitis, diabetes mellitus, dullness, intermittent fever, and excessive sweating.
is a disorder characterized by chronic excretion of large volumes of diluted urine
that is accompanied by extreme thirst caused by hyperosmolarity of body fluids and dehydration.
Diabetes insipidus
is caused by inadequate production of AVP by the posterior pituitary gland.
Central diabetes insipidus
is produced by several disorders that interfere with the interaction between AVP and its receptors in target cells of the kidney
Nephrogenic diabetes insipidus
results mainly from destruction of the supraoptic and paraventricular nuclei
of the hypothalamus, where AVP is produced, or by destruction of the axons carrying AVP to axonal terminal in the pars nervosa
Central diabetes insipidus
PITUITARY-LIKE HORMONES OF THE PLACENTA
- Placental Lactogen
- Gonadotropins
is a protein hormone so-named because it has lactogenic properties in bioassays and
prolactin-like activity in radioreceptor assays
Placental lactogen
a protein has an amino acid
composition similar to ovine prolactin and ovine growth hormone.
Ovine placental lactogen (oPL)
Ovine PL concentrations in blood also are influenced by metabolic state, e.g., fasting
appear to plays roles in regulating mammary gland function, fetal growth, maternal intermediary metabolism, and
ovarian steroidogenesis.
Placental lactogens
are used commonly in veterinary medicine to duplicate the biological effects of LH and FSH
Chorionic gonadotropins
for medical use is obtained from the urine of pregnant women
Human chorionic gonadotropin (hCG)
It closely mimics the effects of LH and has some FSH activity.
Human chorionic gonadotropin (hCG)
In female animals, injected hCG promotes maturation of ovarian follicles, ovulation, and formation of
corpora lutea.
In males, injected hCG stimulates testicular interstitial cells to produce testosterone
It is used clinically to treat ovarian follicular cysts, nymphomania (constant or frequent heat),
cryptorchidism, and male infertility, and to induce or hasten ovulation.
Human chorionic gonadotropin (hCG)
It is used also in dynamic diagnostic tests to determine if remnant testicular tissue is present in castrated male dogs and cats and if remnant ovarian tissue is present in ovariohysterectomized females
Human chorionic gonadotropin (hCG)
glycoproteins
TSH, LH, and FSH, hCG
is a glycoprotein consisting of two nonidentical α and β subunits
hCG
is a single chain of 92 amino acids
α subunit hCG
consists of 145 amino acids
β subunit hCG
The placenta of the mare also produces a gonadotropin called
equine chorionic gonadotropin (eCG) or
pregnant mare serum gonadotropin (PMSG)
is synthesized by the endometrial cups of the
uterus, which in mares begin to develop about
day 36 of pregnancy.
Equine Chorionic Gonadotropin (eCG)
are formed when trophoblastic cells from the
chorion attach to the endometrial epithelium and
migrate into the endometrium
endometrial cups
The cups begin to degenerate by day 60 of gestation but persist
until about day 120 of pregnancy
endometrial cups
In horse mares, eCG appears in maternal blood on about day _____ of pregnancy
day 40
has high FSH-like activity and is administered to cows to induce superovulation for embryo transfer
Equine CG
Beside lactogens and gonadotropins, the _______ also produces peptides with GnRH-, TRH-, GHRH-,
CRH-, and ACTH-like activities.
placenta
Hypothalamus secretes
Growth Hormone-Releasing Hormone (GHRH)
GHRH stimulates anterior Pituitary Somatotropes to release
Growth Hormone
Growth hormone travels to target tissues throughout the body and causes the following affects
- Diabetogenic Effects
- Growth Effects
- Glucose-Sparing Effects
Increases glycogenic breakdown to increase blood glucose
Diabetogenic Effects
Growth hormone travels to target tissues throughout the body. ENUMERATE
- Liver
- Bones
Growth hormone travels to target tissues throughout the body. ENUMERATE
- Liver
- Bones
Liver releases
IGF-1
Anti-Diuretic Hormone
ADH & Vasopressin
Target Organ of Anti-Diuretic Hormone
Kidney
Target Organ of Oxytocin
Breast & Uterus
Target Organ of Growth Hormone
Bone & Soft tissues
Target Organ of ACTH
Adrenal Gland
Hormones produces by Adrenal Gland
Adrenocorticosteroids
Target Organ of TSH
Thyroid Gland
Hormones produced by Thyroid gland
Thyroid Hormones
Target Organ of FSH & LH (ICSH)
Testes
Target Organ of FSH & LH
Ovary & Corpus luteum
Hormones produced by the ovary
Estrogen
Hormones produced by testes
Testosterone
Target Organ of Prolactin
Breast
