6 HP Axis pt. 3 Flashcards
what’s prolactin?
peptide hormone; promotes lactation; produced in the pituitary
what hormones are essential for the initiation and maintenance of milk secretion?
PRL, cortisol
which one has more producing cells: GH or PRL?
GH
what happens to milk production when you do a hypophysectomy?
immediate cessation of milk production
what happens to milk production when you do an adrenalectomy?
gradual reduction in milk production
what needs to happen for milk production to happen?
decrease in estrogen and progesterone, which happens after giving birth
what is perhaps the biggest regulator of PRL?
dopamine
how many genes does the prolactin locus have
1
what kind of receptor engages prolactin?
membrane; recruited
where are prolactin receptors mainly?
mammary glands, but they’re also kidna everywhere
which hormone is responsible for the synthesis and secretion of milk from alveolar epithelial cells?
prolactin
which hormone is responsible for the ejection of milk?
oxytocin
true or false: PRL is required for the development of the mammary gland
false
what hormones play a role in duct development in the breast?
estrogen, GH, adrenal steroids
what hormones play a role in alveolar growth?
estrogen, progesterone, adrenal steroids, PRL
increased levels of PRL (increases/decreases) gonadotropin in males and females
decreases
(high/low) levels of PRL associated with breastfeeding can lead to lactational amenorrhea
high
what’s lactational amenorrhea?
when you’re breastfeeding you don’t have periods
what’s a mitogen?
small peptide/protein that induces cell division
what’s PRL’s significance in immunomodulation?
acts as a mitogen; acts on B and T cells and macrophages
what’s the large precursor molecule of ACTH called?
POMC –> N-POC —> ACTH
what enzyme cleaves POMC
prohormone convertase 1 (PC1)
what hormone is related to ACTH since it’s also derived from POMC?
melanocyte stimulating hormone (MSH)
what does MSH do?
- involved with darkening of skin by stimulating melanocytes to produce melanin to ultimately reduce UV damage
- has morphine-like activity
where does ACTH bind?
receptors in adrenal gland
what does ACTH signaling do to cholesterol?
enhances mobilization of cholesterol from storage; increased conversion to pregnenolone
what G protein does ACTH activate?
Gsa
what hormone controls ACTH secretion?
CRH
expand CRH
Corticotropin-releasing hormone
what affects CRH levels? when is it lowest?
circadian rhythm, stress; midnight
expand ACTH
Adrenocorticotropic hormone
an increase in ACTH will do what to cortisol levels?
promote
an increase in cortisol levels will do what?
decrease hypothalamic and pituitary response, thereby downregulating CRH and ACTH
expand TSH
thyrotropin (thyroid stimulating hormone)
what kind of cells release TSH?
thyrotrophs
what does TSH do?
- regulates thyroid gland using G proteins
- controls formation of thyroid hormones
- stimulates metabolism of thyroid follicular cells
what kinds of cells release LH and FSH?
gonadotrophs
functions of FSH?
females: development of ovarian follicles and estradiol secretion
males: spermatogenesis, production of sex-hormone binding globulin
both: secretion of inhibin (negative feedback on FSH)
functions of LH?
females: steroidogenesis in follicles, induction of ovulation, maintenance of steroidogenesis by the corpus luteum
males: stimulation of testosterone production on Leydig cells
true or false: LH and FSH secretion is pulsatile
true
true or false: in males, inhibin has no effect on LH
true
what is the feedback effects of testosterone?
hypothalamus: pituitary: LH: FSH: they're all negative
which stimulates follicular cells and which stimulates luteal cells?
follicular: FSH
luteal: LH
effect of LH and FSH on pituitary and hypothalamic levels?
mainly negative
where is inhibin produced?
sertoli cells in testes and in the ovaries
true or false: inhibin has no effect on LH secretion in females
true
what is the main cause of disorders of the anterior pituitary?
benign tumors (adenomas)
adenomas are (simple/difficult) to diagnose
difficult - symptoms are pretty generic and they accumulate
can pituitary adenomas serve function?
yes, especially at younger ages. older patients typically have non-functional tumors
what causes adenomas?
hypofunction, hyperfunction, or mass effect
why is it that some adenomas cause visual field defects?
they impinge on optic chiasm or can extend into the cavernous sinuses
what happens when you have a GH deficiency?
decreased: muscle strength, exercise tolerance, diminished libido
increased: body fat
what happens when you have a gonadotropin deficiency?
- oligo/amenorrhea
- diminished libido
- infertility
- hot flashes
- impotence
what happens when you have an ACTH deficiency?
malaise, fatigue, anorexia, hypoglycemia
what happens when you have TSH deficiency?
malaise, leg cramps, fatigue, dry skin, cold intolerance
hypopituitarism leads to what?
deficiencies in hormones like GH, gonadotropin, ACTH, and TSH
how are adenomas treated?
surgery through the nose :/
over secretion of hormones from the anterior pituitary most often include which hormones?
PRL, GH, ACTH
what causes adenomas that over secrete in the anterior pituitary?
- de novo
- lack of feedback control
prolactinoma is usually a result of (over/under) secretion of hormones in the anterior pituitary
over
what can prolactinoma lead to?
oligo/amenorrhea, galactorrhea, infertility, decreased libido, headaches, visual field defects
what happens when you have an over-secretion of GH from adenomas?
- gigantism/acromegaly
- elevated IGFs
expand IGF
insulin-like growth factor
how are adenomas being diagnosed?
MRI imaging
how do you diagnose GH deficiency?
insulin tolerance test, GHRH/arginine test, IGF-1 levels
how do you diagnose gonadotropin deficiency?
sexual history, menstrual history, FSH/LH/estradiol/prolactin/testosterone levels
how do you diagnose ACTH deficiency
AM cortisol, cosyntropin test, insulin tolerance test
how do you diagnose TSH deficiency?
T4 and TSH levels
how do you diagnose prolactinoma
PRL level, drug history, clinical setting
how do you diagnose acromegaly?
IGF-1 level, oral glucose tolerance test
how do you diagnose TSH overproduction?
free T4, T3, TSH levels
how do you treat prolactinoma?
dopamine agonist therapy with bromocriptine to inhibit PRL secretion
how do you treat acromegaly?
somatostatin analogs
how do you treat deficiency states?
replacement of indicated hormone
