Bolick ch 24 Endocrine Flashcards
where is the hypothalamus located
base of the brain stem
how is the hypothalamus linked to the pituitary gland
via the pituitary gland
what two systems are involved in the hypothalamus
neuroendocrine organ
what does the hypothalamus regulate
hormone secretion from the pituitary gland by secretion of specific stimulating and inhibiting hormones
hypothalamic hormones are also referred to as
factors
what are the hypothalamic hormones that are also referred to as factors
GHRH (GH releasing hormone)
SRIF (GH inhibiting hormone or somatostatin)
PIH (prolactin inhibiting hormone or dopamine)
TRF (thyrotropin releasing hormone)
CRF (corticotropin releasing hormone)
GnRH (gonadotropin releasing hormone)
How does the pituitary gland respond to the hypothalamic hormones
by releasing trophic hormones that effect target glands - these glands produce hormones that feed back to the hypothalamus and pituitary gland to regulate the trophic hormone production
what does the anterior pituitary gland regulate
physiological processes including
stress
reproduction
lactation
growth
adenohypophysis
anterior pituitary gland
what does Anterior pituitary gland secrete
Adrenocorticotropic hormone (ACTH)
Luteinizing hormone (LH)
follicle stimulating hormone (FSH)
GH
PRL
thyroid stimulating hormone (TSH)
what secretes aldosterone
adrenal gland - glomerulosa
what does aldosterone do
it is a mineralocorticoid
regulates sodium and water balance
what secretes cortisol
adrenal gland - fasciculata
what does cortisol do
regulates the level of carbohydrate
what secretes progesterone, estrogen, and androgens?
adrenal gland - reticularis
glucocorticoids are responsible for regulating what?
How does it do this?
the body’s response to stress primarily by increasing gluconeogenesis, increasing cardiac output and suppressing immune function
Mineralocorticoids control what and how?
intravascular volume and maintain hemodynamic stability by regulating sodium and water balance
what catecholamines are accountable for the “flight or fight” response when the body receives a threat
epinephrine and norepinephrine
when the body senses that the level of cortisol is low what is that tied to?
Stress - means the body is stressed
what happens when the level of cortisol is low?
activation of the hypothalamic-pituitary-adrenal axis (HPA axis)
a message is sent to the hypothalamus -> release corticotrophin releasing hormone (CRH) ->Anterior pituitary gland -> release adrenocorticotrophic hormone (ACTH) -> adrenal cortex releases cortisol
Okay so your cortisol is low, your body activated the HPA axis…..now, cortisol is no longer needed. what happens next
cortisol travels to the hypothalamus and anterior pituitary -> inhibits further release
the secretion of aldosterone is controlled primarily by
renin-angiotensin system and circulating potassium levels
In response to low circulating volume, what happens in the kidney
Kidney releases renin-> converted to angiotensinogen in the liver forming angiotensin I -> Angiotensin converting enzyme (ACE) in the lungs converts angiotensin I to angiotensin II ->goes to adrenal cortex -> releases aldosterone ->kidney reabsorbs sodium and water -> blood volume increases
adrenal dysfunction can be categorized into what 4 groups
Primary AI (adrenal insufficiency)
Secondary AI
Tertiary AI
relative AI
Primary AI is the result of
can be from what
from a destroyed or inactive adrenal gland or a hormone production failure
Addison disease Adrenal hemorrhage (seen in water-house-Friderichsen syndrome Severe sepsis metastatic infiltration surgical removal granulomatous lesions (TB)
non-traumatic causes of adrenal hemorrhage
ACTH
adrenal vein spasm
thrombosis
normally limited venous drainage of the adrenal in the pathogenesis of this condition
the adrenal gland has a rich arterial supply and a limited venous drainage that is critically dependent on a single vein.
during stress, ACTH secretion increases ->stimulates adrenal arterial blood flow that may exceed the venous drainage capacity and could lead to hemorrhage
adrenal vein thrombosis can occur in adrenal hemorrhage and in association with
sepsis
heparin-induced thrombocytopenia
primary antiphospholipid antibody syndrome
disseminated intravascular coagulation (DIC)
bilat adrenal hemorrhage commonly leads to
acute AI and adrenal crisis
what is the most common infection associated with AI
meningococcemia
Primary AI that is a result of hormone production failure is associated with
CAH (congenital adrenal hyperplasia)
failure to produce corticosteroids
in infancy what is the most common cause of AI
CAH (congenital adrenal hyperplasia)
Secondary AI is associated with the deficiency of
ACTH (adrenocorticotrophic hormone)
remember ACTH travels to the adrenal cortex telling it to release cortisol. (when the body is stressed)
what are most common causes of ACTH (adrenocorticotrophic hormone) deficiency
hypopituitarism secondary to primary pituitary disease
congenital pituitary lesions
developmental anomalies such as anencephaly, holoprosencephaly and craniopharyngiomas
what is the most common reason for ACTH (adrenocorticotrophic hormone) deficiency in childhood
Craniopharyngiomas
which AI is defined as a hypothalamic decrease in CRH (corticotrophin-releasing hormone) secretion or production
Tertiary AI
most common cause of Tertiary AI (adrenal insufficiency)
what populations are at risk
suppression of the HPA axis from prolonged use of glucocorticoids
usually from rapid steroid taper or abrupt steroid withdrawal
think of those using glucocorticoids to manage their disease
asthma history of organ transplant leukemia neurosurgical (pre- and post op) nephrotic syndrome other kidney diseases collagen vascular diseases such as lupus erythematosus and RA
may take HPA axis until more than 1 month after therapy is stopped
In the event that a pt undergoes additional stressors such as a surgical procedure or severe infections, they are assumed to be adrenal deficient for how long after stopping therapy unless what?
1 year after
unless a normal ACTH stimulation test is documented
what is relative AI
every critical ill pt has some degree of relative AI
used when there are high absolute cortisol levels present but they are relatively insufficient to overcome the degree of physiologic stress on the patient
critically ill children with catecholamine-resistant shock commonly show
absolute and relative AI
AI is absent in children with ——- shock
fluid-responsive shock
neonate and HPA axis
immature- can further limit the infants ability to increase cortisol production in response to stress which leads to neonatal AI
How do we screen for congenital adrenal hyperplasia (CAH)
genetic newborn screening
when does CAH usually present
first few weeks of life
what deficiency is associated with CAH
21- hydroxylase deficiency (21-OHD)
Males with CAH usually present in a
salt-wasting crisis at 1-2 weeks of age
accounts for 95% of all cases
what happens in CAH
the missing enzyme (21-HD) reduces the production of cortisol and aldosterone by the adrenal glands -> AI
The pituitary perceives there is not enough cortisol so more cholesterol is delivered. Because there is still reduced production of cortisol and aldosterone, the extra cholesterol is converted into androgen
the excess androgen leads to ambiguous genitalia which makes CAH easier to recognize in female infants
Positive TSI antibody test is associated with
Graves
subacute thyroiditis is associated with a _____ ESR
high
presence of TPO is associated with
Hashiomoto’s disease
