MODULE 2: THE PITUITARY GLAND Flashcards by Danica Mae Araza

The Greek origin of the word pituitary is ________, meaning to spit?

ptuo

How well did you know this?

Not at all

Perfectly

Latin origin of the word pituitary
is _________, meaning mucus.

pituita

How well did you know this?

Not at all

Perfectly

The pituitary gland once was considered the what?

“Master gland of the body”

How well did you know this?

Not at all

Perfectly

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”

How well did you know this?

Not at all

Perfectly

is now known to be controlled by chemical and electrochemical messengers emanating from the brain and other organs and glands

pituitary gland

How well did you know this?

Not at all

Perfectly

is a major controlling participant in the endocrine system

pituitary gland

How well did you know this?

Not at all

Perfectly

produces only closely related steroids

adrenal cortex

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

The pituitary gland is also called

hypophysis

How well did you know this?

Not at all

Perfectly

pituitary gland = hypophysis
Greek: ?
meaning: ?

hypo = under
physis = growth

How well did you know this?

Not at all

Perfectly

It is found ventral to the brain in a dorsal concavity of the sphenoid bone called the
sella turcica or hypophyseal fossa.

pituitary gland

How well did you know this?

Not at all

Perfectly

dorsal concavity of the sphenoid bone called

sella turcica or hypophyseal fossa.

How well did you know this?

Not at all

Perfectly

surrounds the pituitary gland bilaterally and ventrally

sphenoid bone

How well did you know this?

Not at all

Perfectly

It is covered by the dura
mater

sphenoid bone

How well did you know this?

Not at all

Perfectly

a tough fibrous membrane lining the sella turcica and forming the outer layer of the brain

dura mater

How well did you know this?

Not at all

Perfectly

rises dorsally from the pituitary to connect with the hypothalamus

pituitary stalk or infundibulum

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

Anatomical subdivisions of the pituitary gland:

Adenohypophysis (anterior pituitary)
Neurohypophysis (posterior pituitary)

How well did you know this?

Not at all

Perfectly

posterior pituitary also known as

Neurohypophysis

How well did you know this?

Not at all

Perfectly

anterior pituitary also known as

Adenohypophysis

How well did you know this?

Not at all

Perfectly

Three parts of the adenohypophysis:

the pars distalis
the pars tuberalis
the pars intermedia

How well did you know this?

Not at all

Perfectly

part of the anterior pituitary which is the largest part of the adenohypophysis and contains five
populations of cells

pars distalis

How well did you know this?

Not at all

Perfectly

five populations of cells of Pars Distalis

(i) thyrotropes
(ii) gonadotropes
(iii) lactotropes
(iv) corticotropes
(v) somatotropes

How well did you know this?

Not at all

Perfectly

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

1. thyrotropin or thyroid-stimulating hormone (TSH) 2. luteinizing hormone (LH) 3. follicle-stimulating hormone (FSH) 4. prolactin, adrenocorticotropin (ACTH) 5. 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):

1. infundibulum or pituitary stalk 2. 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

1. Adrenocorticotropin 2. Prolactin 3. 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

1. Thyrotropin 2. 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

thyroxine

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:

1. distention of the reproductive tract, particularly in the pregnant female 2. stimulation of the mammary gland by the young 3. 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

1. inducing parturition in some species, or to increase uterine contraction at parturition 2. 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

1. Placental Lactogen 2. 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

1. Diabetogenic Effects 2. Growth Effects 3. Glucose-Sparing Effects

Increases glycogenic breakdown to increase blood glucose

Diabetogenic Effects

Growth hormone travels to target tissues throughout the body. ENUMERATE

1. Liver 2. Bones

Growth hormone travels to target tissues throughout the body. ENUMERATE

1. Liver 2. 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

MODULE 2: THE PITUITARY GLAND Flashcards

(305 cards)