Pituitary and Growth Flashcards
Match system with correct description
(Nervous/Endocrine)
- slower responding system, influences all cells through hormones
- faster responding system, regulates muscle/secretory cell activities via nerve impulses and NTs
- Endocrine
2. Nervous
What is another word for pituitary?
hypophysis
The pituitary gland lies in a pocket of bone called _______ at the base of the brain, just below the _______. It is connected by a stalk containing vessels and nerves.
sella turcica
hypothalamus
The posterior pituitary lobe aka ______ secretes two hormones ____ and ______. They are actually made in the _____ but stored in the _______.
neurohypophysis
oxytocin (OCT) and ADH
hypothalamus
posterior pituitary
The anterior pituitary lobe aka _____ secretes ____ (#) hormones: name them all.
adenohypophysis
6
GH Prolactin ACTH (POMC) Beta-LPH (POMC) FSH LH TSH
The pituitary gland develops embryonically from 2 different _____ regions, the floor of the ___ and the roof of the _____.
The floor of the “” in the hypothalamus develops into the ______ which then extends towards the brain from pituitary, ____, _____, _____, then brain. The roof of the “” loses its connection with the ____ and becomes the ________.
ectodermal
brain
mouth
neurohypophysis
pars nervosa –> infundibulum –> median eminance
mouth
adenohypophysis
in the neurohypophysis, cell bodies in hypothalamic axons terminate at the capillary plexus supplied by what artery?
inferior hypophyseal artery
in the neurohypophysis, peptide hormones in cell bodies of hypothalamus travel as what? to nerve terminals in posterior pituitary
neurosecretory granules
How do neurosecretory granules enter peripheral circulation in posterior pituitary?
through the capillary plexus
T/F: the neurohypophysis has no direct artery supply
FALSE - inferior hypophyseal artery
In the adenohypophysis, stimuli are blood-borne and stimulating/inhibiting hormones travel and are stored where? near a capillary plexus supplied by what?
median eminance
superior hypophyseal artery
in the adenohypophysis, hormones enter capillary plexus and travel down what circulation?
after exiting the second capillary plexus, they reach specific endocrine targets that secrete what?
portal veins
tropic hormones
T/F: OCT and ADH are formed and secreted from endocrine cells
FALSO - nerve cells in hypothalamus –> stored in neurohypophysis
OCT and ADH are synthesized as apart of pre-pro-hormones which include a characteristic _____ (function unknown)
neurophysin
T/F: adenohypophysis has no direct arterial supply but receives blood from veins
TRUE
T/F: adenohypophysis supplied by veins that first drain neural tissue in the median eminance
TRUE
what is the primary function/goal of ADH?
what are the target cells of ADH?
water reabsorption/retention
renal collecting ducts
lack of ADH leads to ______
diabetes insipidus (hypermicturition)
drinking 5 gallons of water will (increase/decrease) ADH secretion in the body and (increase/decrease) water clearance
decrease
increase
what is the primary function/goal of OCT?
Major stimulus?
how is it used clinically?
describe change in OCT levels during labor?
smooth muscle contraction of uterus during parturition (labor)
cervix dilation during labor (positive feedback)
induce labor/control postpartum hemorrhage
OCT low in beginning and increase as labor progresses
T/F: OCT initiates labor by contracting uterine smooth muscle walls
FALSE - OCT not responsible for initiating labor
stimulated by cervix dilation during labor (already started)
what hormone is most abundant of the pituitary hormones?
growth hormone (adenohypophysis)
somatotropes account for ____% of total # of pituitary cells
40-50%
GH induces the secretion of ____ and ______ which circulate bound to a protein complex
IGF-1 and somatomedins
describe the GH short term and long term effects on the body
short term - insulinlike effect, growth promoting on muscle and skeleton
long term - inhibits lipid, aa, carbohydrate metabolism
what 2 hormones may stimulate somatomedin secretion in liver?
insulin and prolactin
T/F: GH regulates secondary endocrine organ
FALSE - GH and prolactin do not regulate secondary endocrine organs
T/F: GH receptors exist in adrenal cortex
TRUE
prolactin is a ____ polypeptide and secretion is under tonic inhibitory control by _____.
single chain
dopamine
what stimuli high levels are associated with increased prolactin?
stress exercise estrogen (prolactin inhibits GnRH so decrease FSH/LH sex hormones) suckling pregnancy
prolactin levels increase with sleep but there is no ______.
circadian rhythm
prolactin in normal levels, induces synthesis of ___ and ____ in mammary glands and _____ with the help of estrogen. However, excess prolactin secretion may lead to ______ (milk discharge from nipple), _______, and ______. prolactin deficiency leads to _______
casein
lactalbumin
breast development
galactorrhea
ovulation
inhibtion of GnRH
failure to lactate
POMC is a prohormone that produces ____ and _____ after proteolytic cleavage.
ACTH and Beta- lipotropin (B-LPH)
what does the carboxyl and amino terminal of POMC become after proteolytic cleavage?
carboxyl - becomes B-LPH
amino - no known function but contains y-MSH which may modulate adrenal cortical synthesis of mineralcorticoids
T/F: ACTH had a circadian rhythm
TRUE
T/F: prolactin and ACTH have circadian rhythms
FALSE - prolactin does NOT, only ACTH does
T/F: CRH (corticotropin releasing hormone) stimulates ACTH secretion
TRUE
what are 4 things that stimulate ACTH release?
hypoglycemia
stress
pyrogens (bacteria causing illness, decrease immunity)
low glucocorticoid levels
what is the most important human pigmentary hormone?
ACTH
T/F: both ACTH and B-LPH induce pigmentation
TRUE
what hormone has activity indistinguishable from LH?
hCG (human chorionic gonadotropin)
hCG is a ______ glycoprotein hormone
placental
FSH, LH, TSH are glycoprotein hormones with common ____ structure but dissimilar subunits, alpha and beta. the alpha subunits have essentially the same _____ but differ in their degrees of _____. the beta subunits are responsible for biologic and immunologic ____ of hormones. the plasma half life is ______.
quaternary amino acid sequence glycosylation specificities 30min-2hr
what are the different half lives of FSH/LH/TSH glycoprotein hormones, hCG, and alpha/beta subunits alone
FSH/LH/TSH: 30min-2hr
hCG: 24-30hrs
subunits: 10-30min
T/F: glycoprotein hormone subunits alpha and beta ALONE have intrinsic biological activity
FALSE - their half life is too short (10-30min)
what causes atrophy of all target endocrine organs?
hypophysectomy
What higher center controls the pituitary gland?
CNS
hypothalamic neurons terminate in the ______ and neural stalk
median eminance
the hypothalamus influences the pituitary through blood-borne factors called _______.
are they inhibitory/stimulatory/both?
if hormones are affected by more than one of these, the pituitary response depends upon what?
hypothalamic releasing hormones/factors
both
relative amount of opposing hormones
what are the 6 hypothalamic releasing hormones?
give their function
ex. x +/- y –> z
GnRH + FSHLH –> sex hormone secretion (both genders)
GHRH + GH –> tissue growth
Somatostatin (SS) - GH –> no tissue growth
TRH + TSH –> thyroid/metabolism
DA (PIF) - prolactin –> no breast development/lactation
CRH + ACTH –> cortisol secretion from adrenal cortex
GnRH is a __-peptide. It is concentrated in the ______. it stimulates pituitary synthesis and secretion of ___ and ____. response to GnRH is modulated by _____. high levels of GnRH block ________. GnRH binds to specific plasma membrane receptors and activates _____.
decapeptide medial basal hypothalamic nuclei FSH and LH sex steroids gonadal steroidogenesis phospholipase C
GHRH is a large peptide that stimulates ____ release from pituitary directly and was initially isolated from a ______
GH
human pancreatic tumor
SS is a ______-peptide which inhibits the release of _____ from normal pituitary and from x-secreting tumors. It is also released from ______
tetra-deca-peptide
GH
D cells of Langerhans Islets
TRH is a ___-peptide that stimulates pituitary synthesis and secretion of ___ and ____. the response decreases with age in (men/women). TRH binds specific plasma membrane receptors in pituitary thryotropes and activates _____.
tripeptide
TSH and prolactin
men
phospholipase C
what two hypothalamic releasing hormones binds to specific plasma membrane receptors and activates phospholipase C?
GnRH and TRH
where is TRH concentration the greatest?
in the hypothalamus
PIF aka ____ tonically inhibits the secretion of _____.
why is prolactin unique in terms of severing the vascular connection b/w hypothalamus and pituitary?
dopamine
prolactin
if the vascular connection between pituitary and hypothalamus is interrupted, prolactin secretions are INCREASED
T/F: obstructing the portal vasculature to pituitary leads to decreased prolactin secretions
FALSE - prolactin secretion is increased if vascular connection is severed
CRH is a large polypeptide that stimulates _____. There may be more than one hypothalamic factor that stimulates ACTH release. _____ may stimulate ACTH via CRH
ACTH
vasopressin
what two types of controls regulate hypothalamic releasing neurons?
hormonal and neuronal
what is long-loop negative feedback? give an example
hormone 3 influences hypothalamus and pituitary directly to inhibit hormone 1’s release and the hypothalamus hormone 1 production
ex. in high levels of cortisol (hormone 3), inhibits hypothalamus secretion of CRH (hormone 1) and pituitary secretion of ACTH (hormone 2) –> reduces cortisol in negative feedback
what is short-loop feedback? give an example
no hormone 3 produced so hormone two negative feedbacks on itself to suppress its own production
ex. prolactin and GH have no secondary endocrine organ, so they negative feedback and suppress their own production
what are the 3 sites of hormone production?
what do these sites need for hormone responses on the target tissues?
hypothalamus
pituitary gland
endocrine/target gland
hormone-specific receptors
what are the 3 main categories of endocrine disorders?
hyposecretion
hypersecretion
hyporesponsiveness of target cells
difference between primary and secondary hyposecretion?
primary - endocrine target gland secretes too little hormone, not functioning normally
ex. decreased cortisol secretion by adrenal gland due to decreased thyroid hormone secretion
ex. decreased secretion of thyroid hormones by thyroid gland due to lack of iodine
secondary - endocrine target gland may be fine but the tropic hormone (pituitary) is too low
ex. decreased TH secretion low so TSH secretion by pituitary is low
difference between primary and secondary hypersecretion?
primary - dysfunctional gland secreting too much hormone, mostly likely due to a tumor
ex. hypersecretion of TH due to thyroid gland tumor
secondary - hyper stimulation by tropic hormone
ex. in cushing’s disease, hypersecretion of ACTH due to a tumor of corticotropes
what is hyporesponsiveness and what are the 3 major causes?
target cells don’t respond to hormone
- lack or deficiency of hormone receptors
ex. type 2 diabetes: deficiency in insulin receptors - post-receptor defect in target cells
ex. normal receptor activity but inability to activate secondary messengers like cAMP or open ion channel - lack of metabolic activation of hormone
ex. enzyme that converts inactive hormone –> active hormone is missing so hormone secreted stays inactive = no response to hormone
T/F: in hyporesponsiveness, plasma hormone concentration if normal/elevated but response to administered hormone is low
TRUE
T/F: in hyporesponsiveness, plasma hormone concentration if depressed but response to administered hormone is high
FALSE - opposite
high plasma hormone concentration because can’t uptake with defective receptors or what not, response will be low
T/F: hypophysectomy in animals was proven fatal
FALSE - not deadly
what is the most dramatic effect of hypophysectomy?
inhibited growth of experimented subject
Match the hypothalamic hormone with the proteins/cells producing pituitary hormones with adenohypophysis hormones
GHRH Dopamine GnRH CRH TRH SS
thyrotropes lactotropes somatotropes corticotropes gonadotropes
ACTH TSH GH prolactin FSH/LH
GnRH - gonadotropes - FSH/LH
GHRH - somatotropes - GH
SS - somatotropes - GH
CRH - corticotropes - ACTh
Dopamine (PIF) - lactotropes - prolactin
TRH - thyrotropes - TSH
what is the single most important hormone for postnatal growth?
GH
what are the 4 functions/effects of GH?
promotes bone lengthening - stimulates maturation/mitosis of chondrocytes
promotes protein synthesis - increases aa uptake, tissue enlargement
stimulates gluconeogenesis - increases hepatic glucose output and inhibits glucose uptake (anti-insulin)
stimulates lipolysis - increases fat metabolism
GH secretes 2 chemical messengers ____ and _____
IFG1/2 and somatomedin C
out of IGFI and IGFII, _____ appears to be the most important mediator of GH actions. _____ may be involved during fetal development. GH acts on liver and secretes ____ into blood and locally.
plasma concentrations of _____ reflect GH availability/rate of growth. Children/adults with GH receptor defect will have (high/low) plasma concentrations of IGFI despite (high/low) concentrations of GH. However, after IGF1 administration, growth is (restored/increased but not restored)
IGF I
IGF II
IGF I
IGF I
low
high
restored
The IGF receptor have _____ activity
tyrosine kinase
T/F: IGF-I in circulation stimulates cell division and bone growth
FALSE - IGF I acts locally in a paracrine/autocrine manner to stimulate cell division and bone growth and IGF in circulation plays only a minor role, if any, in stimulating growth
Where is the main source of IGF I in blood?
liver
both IGF I and II are present in blood at relatively ___ concentrations throughout life and circulate via _______. They do not escape from vasculature and half lives in blood is around ____ hours
high
binding proteins
15 hours
T/F: GH is secreted constantly throughout the day
FALSE - in episodic bursts
GH secretion is largest when associated with ___. males will secrete most of their GH during _____ in a process called _____ whereas females secrete more GH during the ____. GH secretion is most active during _____ (in the lifetime) but persists throughout life. changes in GH secretion with age reflect changes in ____ of secretory pulses.
early hours of sleep
sleep (night)
deep slow wave sleep
day
adolescent growth spurt
magnitude
how does quality of sleep in elderly affect their decreasing lean body mass?
decreasing quality of sleep in elderly –> decrease GH secretions –> loss of bone/muscle growth –> leaner body mass
What hormone provides the primary drive for GH synthesis?
GHRH
T/F: SS inhibits GH secretion by blocking GH synthesis
FALSE - SS reduces or blocks GH secretion in response to GHRH but has little influence on GH synthesis
What 2 types of mechanisms regulate GH secretion?
classical long loop and short loop negative feedback
____ appears to be the result of intermittent secretion of both GHRH and SS.
pulsatility
how does IGF-I inhibit GH secretion?
by inhibiting GHRH –> no GH synthesis
receptors for GHRH, SS, IGF-I are all present on the surface of _____ and control the level of ____ which mediates GH synthesis and secretion
somatotropes
cAMP
what happens to children with a deficiency in thyroid hormones?
linear growth is stunted
what is the results of treating hypothyroid children with thyroid hormone?
How does the results change if there is no GH?
rapid growth and maturation of bone
very little linear growth-promoting effect
T/F: failure to grow in thyroid deficient people is due to decrease in GH receptors# on somatotropes and synthesis
TRUE
During fetal growth, (hormone) _____ serves as the growth-promoting hormone, NOT ____ or ____. locally produced IGF-II determines ______ mass which is the predominant IGF in fetal development.
insulin
NOT GH or thyroid hormone
pancreatic cell mass
insulin is closely related to IGFI and II and can activate ____ receptors.
IGF-I
T/F: insulin can sustain a normal rate of growth without GH
FALSE - GH is needed
T/F: insulin is circulated in blood via plasma-binding proteins
FALSE - IGF I&II but not insulin
Match the IGF with the major physiological role
IGF 1
IGF 2
growth during fetal development
skeletal and cartilage growth
IGF1 - skeletal and cartilage growth
IGF2 - growth during fetal development
what is the source of IGF-1?
liver
where is insulin made?
pancreatic beta cells
T/F: onset of sexual maturation is accompanied by dramatic growth acceleration
TRUE
how does gonadal steroid hormones affect height?
promote linear growth BUT accelerate closing of epiphyses (stop growth)
hypogonadal –> super tall
T/F: IGF and GH levels are highest during puberty
TRUE
_____ rather than androgens are responsible for pubertal growth acceleration and epiphyseal plate maturation
estrogens
___ are the precursors of estrogens and are converted to estrogens by enzyme ______ in gonadal and peripheral tissues. children lacking this enzyme (do/do not) experience growth during puberty despite high levels of androgens
androgens
aromatase
do not
T/F: estrogens decreases in the plasma in both girls and boys early in puberty
FALSE - increases
T/F: estrogens increases in the plasma in both girls and boys late in puberty
FALSE - early puberty
pygmies with the genetic inability to produce _____ have normal GH and ____ levels before puberty, but there is no ____ increase at time of puberty
IGF I
IGF I
IGF I
glucocorticoids are required for ____ of GH and normal growth. excess GC (increase/decrease) GH secretion and also (antagonize/agonize) the effect of GH.
synthesis
decreases
antagonizes
T/F: IGF and insulin are present in fetal pre-natally
TRUE
T/F: GH and T3 are present in fetal pre-natally
FALSE - they appear starting birth
b/w two things were correlated to influence a child’s potential height?
mid parental heigh (MPH) and child’s height
T/F: heritable patterns in height are sex-specific
TRUE
GH hypersecretion is caused by a pituitary ___. before puberty, it causes ____ since GH promotes ____. after puberty, it causes ____ (bone thickening), hand/feet enlargement, increased body hair and glucose (tolerance/intolerance). Excess GH can be treated with _____ analogs (ex. ____) which inhibit GH secretion
tumor gigantism bone lengthening acromegaly intolerance SS octreotide
GH deficiency results in failure to ____, short stature, mild obesity, and delayed ___. caused by lack of _____, lack of GHRH, failure to generate ___ in liver or GH receptor deficiency. However, regardless of plasma GH, optimal height will be attained only if children are _____.
grow puberty somatotropes IGF properly nourished
hypophysectomy causes target gland atrophy in what glands?
adrenal
thyroid
gonads
T/F: acromegaly is the elongation of long bones
FALSE - THICKENING of long bones, width NOT length! you don’t grow
what intravenous fluid would you administer to an unconscious individual with diabetes insipidus? why?
isotonic dextrose
with extreme urination due to lack of ADH, the patient is in diuresis and has hyperosmolality (pee pure water and retain all the ions) –> hypernatremia (high salt). giving patient NaCL isotonic or hypertonic will just increase sodium intake of cells and further create chaos. dextrose is easily metabolized in body so body gets and keeps the free water (isotonic) while the dextrose is metabolized and does not increase osmolality
what is diabetes insipidus?
intense urination and extreme thirst due to lack of ADH
T/F: in removal of adenohypophysis, sex cycle stops
TRUE
