Hypothalamopituitary Axis & Adrenal Flashcards
What are the 3 classes of hormones?
Amines
Steroids
Peptides
Amine hormones are all derivatives of:
Tyrosine
T/F. The amine hormone formed by any given tissue depends on the synthetic enzymes that it possess
TRUE
What enzyme is in the ADRENAL medulla that produces EPINEPHRINE?
Enzyme 3 = PNMT
What hormone that is categorized as an amine is NOT produced in the Adrenal Gland?
Thyroid hormone
A steroid secreting cell would be dominated by (Granular or Agranular) Endoplasmic Reticulum?
Agranular - associated with lipid-soluble substances
The cortical portion of the medulla does not create amines (N, NE), instead if we deliver cholesterol they’ll make:
STEROIDS (cortisol, aldosterone, sex hormones)
What are the 3 zones of the medullary cortex and what specific steroids do they produce?
Zona Reticularis –> Androgens,
Zona Fasciculata –> Cortisol,
Zona Glomerulosa –> Aldosterone
What is an example of a GLUCOcorticoid?
CORTISOL
What is an example of a MINERALOcorticoid?
Aldosterone
What is an example of an Androgen?
DHEA and androstenedione
What is the FIRST RATE-LIMITING enzyme involved in creating steroids from Cholesterol?
Cholesterol desmolase
Which hormone controls the activity of Cholesterol desmolase?
ACTH
What other hormone can step in and activate cholesterol desmolase in the absence of ACTH?
Luteinizing hormone (LH)
What role does ANGIOTENSIN II have in steroid syntheisis?
It activates an enzyme (aldosterone synthase) in the last step in the formation of ALDOSTERONE (a mineralocorticoid)
What enzyme is another regulatory step in the formation of Aldosterone?
21B-hydroxylase
What enzyme is CRUCIAL in the formation of Cortisol and Androgens?
17a - hydroxylase
T/F. Steroid hormones have a direct action on a systolic or nuclear receptor that controls gene transcription.
True (they are lipid-soluble and do not require a receptor and can move in cell freely into cytoplasm to influence)
When GROWTH HORMONE binds to its TYROSINE KINASE receptor it phosphorylates a second messenger to have a DIRECT EFFECT ON_______
TRANSCRIPTION
T/F. Like growth hormone, CORTISOL is released in a pulsatile fashion throughout the day.
TRUE - it has a DIURNAL pattern of release
The LOWEST secretory rate of CORTISOL occurs:
a. Late morning
b. Afternoon
c. Late evening/early morning
C - preparing for sleep!
What does the HPA in “HPA-Axis” stand for?
Hypothalamus,
Pituitary,
Adrenal Gland
Neural inputs from the brain travel from the _______ to the ______________ to the ____________, which releases cortisol onto TARGET tissues.
Hypothalamus,
Anterior Pituitary,
Adrenal gland
_____ causes the Hypothalmus to release ______ which travels to the _______ Pituitary to stimulate it to release _________, which travels to the Adrenal Gland to release ______, which has metabolic effects on target tissues.
STRESS causes the Hypothalmus to release CRH which travels to the ANTERIOR Pituitary to stimulate it to release _ACTH, which travels to the Adrenal Gland to release _CORTISOL, which has metabolic effects on target tissues.
Which steroid has all the SAME FEEDBACK mechanisms as cortisol, and such can be used clinically to determine if the HPA axis is defective.
DEXAMETHASONE
T/F. Glucosteroids stimulate bone formation.
FALSE - it inhibits it (most of its actions are CATABOLIC)
Cortisol acts in unison or in contradiction to INSULIN?
CONTRADICTION - has ANTI-Insulin effects (is catabolic)
What is Cortisol’s effect on vascular responsiveness to catecholamines (E, NE)?
Produces adrenergic receptors and ENHANCES responsiveness of the system.
What effects does Cortisol have on GFR?
Increase. It increases the sympathetic NS response
What electrolyte findings are related to Aldosterone?
Increase K + H SECRETION (becomes MORE alkaline),
Increase Na REABSORPTION
T/F. Biosynthesis of ALDOSTERONE depends, in part on the secretion of ACTH.
True. - All steroids do
What are some STIMULATORY factors on ACTH secretion and thus steroid formation?
STRESS!,
Decreased blood cortisol levels (+feedback),
Beta-blockers
What are some INHIBITORY factors on ACTH secretion and thus steroid formation?
Increased blood cortisol levels (- feedback),
Opioids,
somatostatin
What are some SYMPTOMS of ADRENAL INSUFFICIENCY and thus DECREASED CORTISOL?
weakness, lethargy, appetite loss, low BP, hypoglycemia,
Would adrenal insufficiency be primary or secondary if labs showed low ACTH AND low Cortisol levels?
SECONDARY - due to loss of pituitary
If ACTH was High and Cortisol was still low, where is the problem?
PRIMARY ADRENAL INSUFFICIENCY. The pituitary is pumping out enough ACTH.
Primary Adrenal HYPERplasia, caused by CUSHING’s SYNDROME, would have what kind of Cortisol and ACTH levels?
HIGH cortisol,
LOW ACTH
If BOTH ACTH and CORTISOL are ELEVATED, what could be the cause?
CUSHING’S DISEASE - tumor in the PITUITARY
What are some clinical manifestations of Cushing’s Disease?
Moon facies,
Buffalo hump,
thinning skin
What’s the fancy name for PRIMARY ADRENAL INSUFFICIENCY?
Addison’s Disease
If Cortisol levels are low, like in Addison’s disease and pituitary insufficiency, what would we expect the BP to be like?
LOW
In Excess cortisol levels, like in Cushings syndrome and disease, what would be expect BP to be?
HIGH
What are potential adverse effects of being deficient in 17a-hydroxylase, the enzyme for cortisol and Androgen production?
a MASCUlNE HYPOtensive person
What 2 PEPTIDE HORMONES are released from the POSTERIOR PITUITARY?
ADH (Vasopressin)
&
Oxytocin
How is the travel of the signal from the HYPOT to the Anterior pituitary different than that of the POSTERIOR pituitary?
Anterior works through a chain of releasing another hormone (CRF). The posterior travels through the stalk via neurons and doesn’t release any hormones until it gets all the way there.
What is the name of the stalk that connects the Hypothalamus to the Pituitary?
INFUNDIBULUM
What is contained in the Infundibulum and which portion of the Pituitary receives its signals from which?
Neurons –> POSTERIOR,
Blood vessels –> ANTERIOR
T/F. The Anterior and Posterior divisions of the pituitary are derived from the same embryonic origins.
FALSE!,
Posterior (neurohypophysis)<– Rathke’s Pouch
2 separate NUCLEI in the Hypothalamus will carry signals down their axons to create 2 peptides released at POSTERIOR pituitary, what are they?
Supraoptic –> ADH,
Paraventricular –> Oxytocin
What does Oxytocin act on?
Smooth muscle of breast and uterus
Why do we want the nucleus of the Supraoptic to be situated right next to osmolarity sensing cells?
Because ti will determine how much ADH we need (antidiuretic hormone).
Hyperosmotic = Increase release of ADH
These CAPILLARIES at the base of the hypothalamus flow through the infundibulm and target the ANTERIOR PITUITARY to carry hormones in the HPA axis.
MEDIAN EMINENCE
Beside just CRH (cortisol releasing hormone), there are many hormones being released by the HYPOTHALAMUS that target the ANTERIOR pituitary, these are called:
HYPOPHYSIOTROPHIC HORMONES
What are some examples of Hypophysiotrophic hormones being secreted by the Hypothalamus, and what do they secrete at Ant PIT?
CRH --> ACTH, GnRh --> FSH, LH, GHRH --> Growth hormone, SS (somatostatin), TRH (thyroid releasing hormone) --> TSH, DA -->Prolactin
Of the hormones that are secreted by the Anterior Pituitary, which ones have a “UNIVERSAL” effect and target all cells?
Growth factor,
thyroid,
Cortisol
What are the effects of Growth hormone at the liver and organs and tissues?
Liver –> secretes IGF-1 (somatomedin) –> PROMOTES CELL DIVISION
Organs/Tissues –> Protein synthesis + ANTI-INSULIN effects = CHO & Lipid metabolism
What is the principle hormone for POSTNATAL GROWTH?
GH
The effects of growth hormone are not direct, but instead through:
Somatomedin (IGF-1)
Who are in the GANG OF FIVE ?
All have Anti-Insulin effects that work in CONCERT
- Glucagon
- Cortisol
- Epinephrine
- Thyroid hormone
- Growth hormone
What factors INCREASE GH secretion?
Hypoglycemia/fasting,
slow-eave sleep,
Fever/emotional trauma,
Estrogen
What factors DECREASE GH secretion?
Obesity, REM sleep, Cortisol, Progesterone, Somatostatin
T/F. Obesity will retard growth
TRUE
Linear growth of long bones end with the closure of what?
Epiphyseal plate at end of puberty
Different growth rate for various organs are seen, which organ develops first?
Brain, followed by height and reproductive organs last
Most ENDOCRINE DISORDERS fall into these 4 categories:
- HYPOsecretion (too little)
- HYPERsecretion
- HYPOsensitivity (reduced response)
- HYPERsensitivity
The most common cause of HYPERsecretion is:
TUMOR
Excess GH in PRE-Puberty (BEFORE epiphyseal plate closes), can result in what?
GIGANTISM
Excess GH in POST-Puberty (AFTER plate closes), can result in what?
ACROMEGALY
Decrease GH in PRE-PUBERTY, can result in what?
DWARFISM
