HP Adrenal Axis 1 Flashcards
The Pituitary Gland
Small outgrowth of the _______
Size of _____ ( ___cm; apprx ___mg)
forebrain
half a pea
<1; 500
Two functional parts
______hypophysis (_______ pituitary)
______hypophysis (_______ pituitary)
Adeno; anterior
Neuro; posterior
Two functional parts
The Move together during development(T/F)
Adenohypophysis
From ________ – _______ above ____
Neurohypophysis
From _______
T
Rathke’s pouch; ectoderm above mouth
Hypothalamus
Blood and nerve supply
Hypothalamus
Anterior pituitary
Blood supply from ________ of hypothalamus – a _______
Posterior pituitary
_________ and ________ in hypothalamus
median eminence; portal system
Supraoptic and paraventricular nuclei
Hypothalamic neurons release hormones directly into ______
capillary plexus
Posterior pituitary hormones
Vasopressin/Antidiuretic hormone (ADH)
Produced by ________
It Conserves _____
________ urine
Water reabsorption by _________
Deficiency:__________
Extreme ______ and ______
Increase plasma _______ and _______
Excess: inappropriate ADH “water intoxication”
supraoptic nucleus
water
Concentrates ; collecting tubule
diabetes insipidus ; thirst and polyuria
sodium and osmolality
Posterior pituitary hormones
Oxytocin
________________
Milk let-down
Anterior pituitary hormones
List 6
TSH: Thyroid stimulating hormone
ACTH: Adrenocorticotrophic hormone
LH: Luteinising hormone
FSH: Follicle stimulating hormone
Prolactin
GH: Growth hormone
HYPOTHALAMUS - corticotropin releasing hormone (CRH)
Release is Influenced by ______signals e.g. Stress, and regulated by ————- from ______
Action is to stimulate the ________ to synthesize and release ——-
Higher centre
negative feed back; free-Cortisol.
anterior Pituitary
ACTH
PITUITARY- adrenocorticotropic hormone (ACTH)
Precursor is ————-.
Released in response to ——
Main action is acute regulation of steriodogenesis in ______mainly zonal _______ hence;
maintain intergrity of adrenal cortex tissue :
-stimulation of ___________ synthesis
-with minimal effect on _______ synthesis
- Also stimulates ______ to produce ———.
pre-opiomelanocortin
CRH; adrenal gland ; fasciculata
glucocorticoid (Cortisol)
mineralocorticoid (Aldosterone)
melanocytes; melanin
List the zones, and the hormones
zona _______ ; _______
zona ————-;_______
zona ————-;_________
glomerulosa ; mineralocorticoids (aldosterone)
fasiculata ; glucocorticoids (cortisol)
reticularis; sex steroids (androgens)
Steroids are lipophilic, (low or high?) -molecular weight compounds derived from ________ that play a number of important physiological roles.
Low
cholesterol
The steroid hormones are synthesized mainly by endocrine glands such as the _______,__________ and during gestation by the ___________, and are then released into the blood circulation.
They act both on ———- tissues and the ___________
gonads (testis and ovary), the adrenals
fetoplacental unit
peripheral target
central nervous system (CNS).
Thus, gonadal steroids influence the —————— of the genitalia and of the ______, determine secondary sexual characteristics during development and sexual maturation, contribute to the ____________ in adulthood and control or modulate sexual behaviour.
sexual differentiation; brain
maintenance of their functional state
circulating steroids are extensively metabolised _____, notably in the ———, and in their ________, where conversion to an active form is sometimes required before they can elicit their biological responses.
peripherally; liver; target tissues
• Steroid metabolism is therefore important not only for the production of these hormones, but also for the regulation of their cellular and physiological actions
T/F
T
The parent compound from which all steroids are derived is ______ which has the ———— structure.
cholesterol
perhydrocyclopentanophenanthrene
___________ give rise to a great number of possible stereoisomers
Functional groups
Stereoisomerism is very important for biological activity
T/F
T
Cholesterol can be synthetised in ____ steroid- producing tissues from_____ in the liver, the ____ and the _____
all
acetate
skin; intestinal mucosa
Steroid hormone formation in endocrine glands relies mostly on _________ ( ——- cholesterol).
exogenous cholesterol
plasma
Androgen formation in the adrenals is limited to ————- and ________, whereas in the testes the presence of 17ß- hydroxysteroid dehydrogenase (17HSD) in _______ cells (under the control of LH) ensures the formation of ________, the principal “ male “ hormone.
dehydroepiandrosterone
androstenedione
Leydig
testosterone
________ is the main glucocorticoid secreted by human adrenal glands.
Cortisol
Progesterone is produced by the ________ during the first 6-8 weeks of gestation, but during pregnancy the main source for this steroid is the ______.
corpus luteum
placenta
Estrogen levels (and that of its metabolite _____) rise markedly during gestation.
The substrate for estrogen biosynthesis in the fetoplacental unit is ____________ which is obtained from the ______ bloodstream
estriol
dehydroepiandrosterone sulfate (DHEAS)
fetomaternal
Aromatase activity is mainly found in the _______,_________, and ———— , and is also membrane- bound.
Its substrate is either _______ or ______
ovary, the placenta and the brain
4- androstenedione or testosterone.
Inability to secrete normal levels of adrenals steroids may result in ___________________________ following hyperstimulation by _________________
In the majority of cases, this syndrome is due to _____________ , and is associated with increased adrenal androgen secretion and ____________ in girls
CONGENITAL ADRENAL HYPERPLASIA (CAH)
ACTH
21-hydroxylase deficiency
Partial virilization
Less common adrenal enzyme deficiencies involve either ________ (with a possible increase in ________ levels) or __________ ( ________ may be deficient with normal levels of ———-).
17-hydroxylase
mineralocorticoid
18- hydroxylase
aldosterone; cortisol
Defects in testicular androgen synthesis (17,20-desmolase or 17ß- hydroxysteroid dehydrogenase deficiency) can lead to ______________________
However, in more than 80% of the cases, it is assumed to result from abnormalities in __________________________
male pseudohermaphroditism.
androgen action at the target cell level
Defects of excess secretion of steroid hormones like ___________ (excess cortisol)
Also defect of specific enzyme deficiency like ___________ (Aldosterone deficiency)
cushings syndrome
Addison’s syndrome
Steroids are released into the blood circulation as soon as they are formed
T/F
T
Secretion rates are therefore directly related to the ___________ and ______
biosynthetic activity of the gland and to the blood flow rate.
unconjugated steroids are found mostly _________________ .
Binding to plasma ______ (which accounts for ____% of the bound fraction) is not specific, whereas binding to either _____________________ or the __________________ is based on more stringent stereospecific criteria
bound to carrier proteins
albumin; 20-50
corticosteroid-binding globulin (CBG) or the sex hormone-binding globulin (SHBG)
the sex hormone-binding globulin (SHBG)
sometimes called __________________
sex steroid-binding protein” SBP]
The “ free fraction “ ( _____ % of total plasma concentration) is usually considered to represent the biologically active fraction (i.e. hormone that is directly available for action)
1-10
Other major roles of plasma binding proteins include
• Act as a “ _______ “
•_________ for active hormones
• protect the hormone from ________ (notably by _____ enzymes) and increase the half-life of biologically active form
buffer
reservoir
peripheral metabolism
liver
Peripheral metabolism of circulating steroids
They have a very (small or latge?) distribution volume.
In their target tissues, steroids are concentrated by an __________ which relies on their __________
High concentration of steroids are also found in _______ though this is not a _____ for hormone action.
In the human male, adipose tissue contains _______ activity, and seems to be the main source of androgen-derived ____ found in the circulation
Most of the peripheral metabolism occurs in the _____ and to some extent in the ______, which are the major sites of hormone inactivation and elimination
Large
uptake mechanism ; binding to intracellular proteins
adipose tissue; target
aromatase; estrogens
liver; kidneys
Steroid in target tissues
Steroids have ____________-term effects.
both short- and long
Steroid in target tissues
Long-term effects (lasting from hours to days) usually involve interaction of the hormone with a _________
The steroid-receptor complex regulates __________
specific receptor
gene transcription
Certain hormones need be converted to active form before binding to specific receptors in target tissues
This metabolic activation step is either an absolute prerequisite or a way of achieving a range of complex effects which involve interaction with more than one type of receptor.
T/F
T
Conversion of testosterone to ______ is required for its action on prostate growth and function
whereas
aromatization to _______ in the ____ is mandatory for some of its developmental, neuroendocrine and behavioral effects.
5α-DHT
estradiol-17ß; brain
When conversion of the circulating hormone is required for its action, the original compound is sometime called a _________.
prehormone
Various disorders can result from a genetic defect in target tissue metabolism.
• In male pseudohermaphroditism (i.e. _____ individuals with a _____ phenotype) due to _______ deficiency.
Individuals with this _______ disorder have ______ plasma levels of testosterone, but this hormone _________________, in the target tissues and is ineffective.
This type of androgen resistance syndrome results notably in an abnormal ____________ of the male genitalia.
46,XY; feminised; 5α-reductase
autosomal recessive
normal ; cannot be converted to its active metabolite, 5α-DHT
sexual differentiation
V
F
