anterior pituitary hormones Flashcards
list anterior pituitary hormones
- thyroid stimulating hormone (TSH/thyrotropin)
- adrenocorticotropin hormone (ACTH/corticotropin)
- growth hormone (GH/somatotroin)
- prolactin (PRL)
- follicle-stimulating hormone (FSH)
- luteinizing hormone (LH)
list the anterior pituitary cells as defined by the hormones they produce and where they are located, and what they target
pars distalis:
- thyrotropes: TSH = thyroid T3/T4
- corticotropes: ACTH = adrenal cortex cortisol
- gonadotropes: FSH and LH = gonads sex steroids
- somatotropes: GH = liver tissues etc. IGFs
- lactotropes: PRL = mammary gland milk
pars intermedia (single cell type)
- melanotropes: MSH
somatotropes and lactotropes stain
red
corticotropes, thyrotropes and gonadotropes stain
blue
which hormones regulate somatotropin secretion
- GH releasing hormone
- somatostatin
- ghrelin
what do growth hormones do
- stimulates IGF-1 secretion from liver
- growth
- stimulates protein synthesis
- stimulates lipolysis
- inhibits glucose utilization
explain why lactotropes stain differently and when
- stain when they are storing PRL in the cytoplasm
- stain poorly when PRL is released
what regulates lactotropes
- tonic inhibition by dopamine
- can be stimulated by TRH
- hypertrophy during pregnancy in preparation for lactation
what do coticotropes do
- produce the POMC prohormone: proopiomelanocortin
- proteolytic hormones cleave POMC into ACTH, MSH, etc
what are corticotropes regulated by
- corticotropin releasing hormone
- tonic stimulation (more CRH increases ACTH secretion, less CRH decreases ACTH secretion)
- negative feedback loop
what does FSH do
females: follicle development (ovary) and estradiol (an estrogen) production
male: support spermatogenesis by sertoli cells
what do luteinizing hormones
female: stimulates ovulation, corpus luteum development and progesterone
male: maintenance of leydig cells and therefore testosterone production
what are gonadotropes regulated by
- GnRH form hypothalamus
- negative feedback loop
what do thyrotropes do
- synthesize TSH
- acts on follicular cells of the thyroid gland (produces thyroglobulin that will become triiodothyronine and thyroxine
what are thyrotropes regulated by
- thyrotropin-releasing hormone (TRH) from the hypothalamus
- tonic stimulation
describe the pars intermedia
- series of small cystic cavaties
- follicles filled with colloid
- residual lumen of rathke pouch
- cells: basophils and chromophobes
- extends into the pars nervosa
- referred to as melanotropes in horses
what is a closed feedback loop
- target cells secrete hormones that affect their own secretion
- feedback regulation (usually negative)
what is an open feedback loop
- no direct feedback
- stopped by removal of stimulus or depletion of biochemicals
- example: stimulation of milk letdown
what is a positive feedback loop
rare
- when secretion of a hormone increases in response to feedback from the organ
- an amplification process
what is a negative feedback loop
- the most common type of feedback
- short feedback loop vs long feedback loop
describe pituitary dwarfism
- most common in GSD
- caused by cyst in place of the anterior pituitary gland
- lower GH = small dog
- lower ACTH = hypoadrenocoticism
- lower TSH = hypothyroidism
- most die as stillborns, some live to 4/5
- hormone supplementation limited due to species specificity
