Anterior Pituitary Flashcards
(27 cards)
What stimulates release of ACTH? Which hypothalamic hormone signals its release?
Stress, hypoglycemia, fever
CRH
What type of hormone is ACTH? What’s its half life?
Peptide hormone - 39 AA
less than 20 min
What does ACTH stimulate?
Secretion of glucocorticoids, androgens, mineralocorticoids
Which hypothalamic hormone stimulates release of TSH?
TRH
What type of hormone is TSH?
Glycoprotein hormone composed of alpha and beta chains
What does TSH do? What inhibits it?
Stimulates TH production from thyroid gland
Inhibited by TH (negative feedback) and somatostatin
What hypothalamic hormone stimulates release of LH and FSH? What do they trigger?
GnRH, trigger E2 secretion from ovary –> ovulation
What types of cells does LH act on? What does it do
Interstitial cells of ovary, stimulating production of estrogens, androgens and progesterone
Acts on the Leydig cells of the testes to make testosterone
What types of cells does FSH act on? What does it do? What suppresses FSH secretion
Germ cells - controls gametogenesis in both men and women
Stimulates Sertoli cells in men
Inhibin from Sertoli cells suppresses FSH secretion
What type of hormone is GH?
Polypeptide
What has a positive effect on pulsatile secretion of GH?
GHRH, Ghrelin (moderately)
What has a negative effect on secretion of GH?
Somatostatin
What cytokine family receptors are used by GH? For what processes?
JAK-STAT2 pathway - nuclear effects leading to growth
JAK-MAPK/Shc pathway - cytosolic effects leading to metabolism
How does GH stimulate metabolic growth? (what happens in tissues)
Adipose - decrease glucose uptake, increase lipolysis (decrease adiposity)
Muscle - decrease glucose uptake, uptake AA, synthesize proteins (increase lean body mass)
Liver - gluconeogenesis, protein synthesis, IGF-1
Increases organ size and function
What molecule, whose production is stimulated by GH by activating its gene transcription, stimulates cellular growth? How does it do so?
IGF-1/somatomedin-C
Stimulates nucleic acid and protein synthesis in other organs and chondrocytes
What nutritional factors stimulate GH secretion?
Hypoglycemia, FFA decrease, AA increase, fasting (acute), prolonged caloric deprivation, stress, exercise
What nutritional factors inhibit GH secretion?
Hyperlycemia, FFA increase, GH and IGF-1 (feedback)
What other hormone stimulates insulin secretion, but only if GH is present?
Insulin
What nutritional factors inhibit IGF-1 secretion? What’s unique about this?
Fasting, protein deprivation, insulin deficiency
Fasting would normally activate GH, so these factors can override GH’s stimulatory effect - as a result fasting will decrease cellular growth, but increase caloric metabolization
What condition results from excess GH before plates fuse? What do these patients show metabolically?
Gigantism - have high FFAs, high glucose levels, lean body mass
How does somatostatin inhibit GH release?
Binds to receptor in anterior pituitary, activates Gi protein to decrease cAMP levels
How does GHRH stimulate GH release?
Binds to receptor in anterior pituitary, activates Gs protein to increase cAMP and PKA levels, so GH gene is transcribed
There is immediate release of pre-made hormone, then storage and long-term release of newly synthesized hormone
What type of cell is GH synthesized in and secreted from?
Somatotrophic cells
How does diurnal pulsatility change in adults?
Metabolic effects of GH predominate over growth effects
