EXAM 3 Study guide Flashcards
negative feedback
Most common
regulation self limiting prevents over-excitation
positive feedback
is rare
explosive and self-reinforcing a hormone has biologic action that causes more secretion of the hormone
-example: LH surge before ovulation - result of positive fb of estrogen on anterior pituitary. LH then acts on ovaries and causes secretion of estrogen.
also seen in blood clotting and labor pain
- A = Progesterone is secreted during the luteal phase of the menstrual cycle
- B = Estradiol from the Ovary (the ovarian granulosa cells contain high concentrations of aromatase and convert testosterone to estradiol
- C = Estradiol dudring the luteal phase of the cycle; Corpus Luteum is the source of the estradiol; as it prepares the uterus to receive a fertilized egg.
- D = Postive feedback of ESTROGEN on the anterior pituitary. Show the LH surge that initiates ovulation at mid-cycle. The LH surge is caused by increasing estrogen levels from the developing ovarian follicle. increased estrogen (by + fb) stimulatees the anterior pituitary to secrete LH and FSH.
X =
X = indicated the peak level of HCG (human chorionic gonadotropin) at week nine which then declines. The source of HCG is placenta.
PDE inhibitors:
caffeine
theophylline
aminophylline
**results in increased cAMP levels
ativation of tyrosine kinase:
insulin
IGF - 1
mechanism of action for:
Nitric oxide
Atrial natriuretic peptide (ANP)
cGMP
Anterior pituitary supplied by:
Artery: hypothalamic hypophysial portal vessels
what plexus brings blood to anterior pituitary?
primary capillary plexus
Posterior pituitary communication from the paraventricular nucleaus via the
by neurons via the hypothalamic hypophysial tract
the active gland and the storage site of the pituitary system
Active gland = anterior pituitary
Storage = posterior pituitary (secretions come from hypothalamus via supra optic and paraventricular nuclei
patient complains of visual disturbances with pituitary tumor, why?
compression of optic chiasm / optic tract
rathke’s pouch - what is it developing?
== gives rise to anterior pituitary
- depression in the roof of developing mouth in front of the buccopharyngeal membrane…
- present during embryogenesis
- the dorsal half of Rathke’s pouch forms intermediate lobe
pituitary gland (hypophysis) located in
sella turcica of sphenoid bone
hypopituitarisim causes:
all or some pituitary hormones may be absent
MCC: pituitary tumors
pituitary infart; sheehan’s syndrome
trauma
Radiation
Surgery
Infiltrative dx (TB, sarcoid, hemochromatosis)
Sheehan’s syndrome is:
anterior pituitary infarct during childbirth
due to PPHemorrhage
Clinical features of Hypopituitarism:
- Low GH - growth failure; low muscle mass
- Low ACTH - adrenal insufficiency
- Low Prolactin - unable to lactate
- Low TSH - hypothyroidism
- Low FSH/LH - impotence, testicular/uterine/ovary atrophy, amenorrhea
- Low MSH - pallor of skin and hair (decreased pigmentation)
Hormones of Anterior Pituitary
- GH,
- Prolactin
- THS
- LH
- FSH
- ACTH
- beta-lipoprotein
hormones of posterior pituitary
- Antidiuretic Hormone (ADH) or AVP
- Oxytocine
Growth Hormone (Somatotropin)
- is the most important H for normal growth
- Released in pulsatile fashion
- What factors INCREASE secretion?
- What factors DECREASE secretion?
- Increase:
- exercise
- hypoglycemia
- puberty
- sleep
- stress
- starvation
- Decrease:
- hyperglycemia
- obesity
- pregnancy
GH deficiency:
- growth stunt
- mild obestiy
- delayed puberty
caused by: lack of GH, hypothalamic dysfunction, GH receptor deficiency (end organ deficiency)
Excess GH:
- causes
- presentation
- Causes:
- pituitary adenoma producing GH
- Before puberty - Gigantism
- After puberty - Acromegaly
- causes glucose intolerance,
- increased bone growth,
- increased organ size
Acromegaly presentation:
increased GH after puberty - pituitary adenoma
- enlarged features (hands feet, nose, orbits, jaw bone) TONGUE and organs
- Hyperglycemia = Increased IGF-1,
- Tunnel vision “ bitemporal hemianopia” from compression of optic chiasm
tx for acromegaly
Octreotide (somatostain) to supress GH
- radiation
- transphenoidal resection
Prolactin is inhibited by
dopamine
negative feedback control
prolactin inhibits ovulation by decreasing synthesis and release of
gonadotropin releasing hormone (GnRH) - no FSH/LH
Bromocriptine:
dopamine agonist reduces prolactin secretion when in excess
Factors that Increase and decrease prolactin secretion:
- Increase:
- estrogen (pregnancy)
- breast feeding
- sleep
- stress
- TRH
- Dopamin antagonist (antipsyhotic meds)
- Decrease:
- dopamine
- Bromocriptine (dopamine agonist)
- somatostatin
ADH and oxytocin are synthesized where?
-supraoptic and paraventricular hypothalamic nuclei