Flashcards in Pituitary Physiology Deck (55):
Pituitary sits in the _____
Deficiency in ____ or ____ transcription factors will result in panhypopituitary.
Prop1 or Pit1
Somatotrope secretes ____
Thyrotrope secretes ____
Lactotrope secretes ____
Gonadotrope secretes ____
Glycoprotein AP hormones
TSH/LH/FSH: same alpha subunit, different beta subunit
ACTH is derived from ____
T/F Both GH and prolactin can activate the prolactin receptor
T --> structural homology
Which hormone? Stimulates secretion of IGF1 from liver and stimulates lipid and CHO metabolism.
Which hormone? Stimulates synthesis and secretion of thyroid hormones and regulates thyroid cell proliferation and survival.
Which hormone? Stimulates synthesis and secreetion of adrenal cortex steroids and proliferation and survival of adrenal cortex cells.
Which hormone? Stimulates milk production.
Which hormone? Stimulates ovulation and progesterone synthesis. Gametogenesis in males and synthesis/secretion of testosterone.
Which hormone? Stimulates estrogen synthesis and follicular growth. Spermatogenesis in males.
Which hormones share the same alpha subunit in their structure?
Loss of ______ by target hormones results in pituitary trophic hormone hypo/hypersecretion and hypo/hyperplasia of pituitary cells as seen in severe hypothyroidism or hypoadrenalism.
feedback inhibition --> hypersecretion and hyperplasia
burst/spike of hormon secretion that can be superimposed on circadian rhythm--> important for things like reproduction
Hypothyroidism caused by thyroid gland destruction can lead to hypertrophy of which gland?
Hypothalamic CRH (stimulatory trophic factor) --> AP ACTH --> Adrenal Cortex cortisol --> feedback to hypothalamus and pituitary
T/F melanotropin and ACTH are derived from the same molecule
T --> cleaved from POMC (pro-opiomelanocortin)
Stimuli for CRH secretion
stress, hypoglycemia, anxiety, depression, alpha/beta adrengergic agonists --> peaks before waking
Inhibitor of ACTH
What laboratory picture is expected in a patient with excessive cortisol production by an adrenal tumor?
High cortisol, low ACTH
Student is studying for at test at 1 am. What is his cortisol profile?
high ACTH, high cortisol --> stress can overcome circadian rhythm
Student is asleep at 1 am. What is his cortisol profile?
low ACTH, low cortisol
Hypothalamic-Pituitary-Growth Hormone axis
hypothalamic ghrh -->pituitary GH -->liver IGF1--> with negative feedback from hypothalamic somatostatin, liver IGF1 and pituitary GH
Stimulators of GHRH
hypoglycemia, dietary protein, exercise
GHRH is inhibited by ____
IGF1 and GH
T/F SST are present in many tissues
T --> hypothalamus, GI tract, pancreas
TSH, PRL, glucagon, insulin, and GH release
stimulates post natal growth indirectly via IGF1--> declines from puberty onward, pulsatile secretion
GH half life
What is the measure of GH production?
IGF1 --> cannot get accurate GH measurement because of short half life and b/c amplitude and frequency of pulses are affected by many variables
Which physiologic process will lead to a decrease in GH production?
reduction in GHRH, increase in somatostatin, increase in IGF1
breast neural stimulus -->hypothalamic PRF --> pituitary prolactin --> mammary gland //hypothalamic dopamine inhibits the pituitary, pituitary prolactin inhibits hypothalamic GnRH, and ovarian E2 stimulates the pituitary
Inhibitory feedback in prolactin axis
Milk does not feedback!
prolactin is inhibited by
prolactin negatively regulates ______ via hypothalamus GnRH
T/F high prolactin negatively regulates HPG axis and can explain amenorrhea in a nursing woman
Why do we treat hyperprolactinemia in men?
to treat hypogonadism (via GnRH)
hypothalmic GnRH --> pituitary FSH/LH --> positive/negative feedback from ovary/testis estrogens (on both hypothalamus and pituitary), negative feedback from inhibin (on pituitary), negative testosterone/progesterone feedback on hypothalamus
Effect of constant GnRH infusion
inhibition of LH/FSH --> which normally are pulsatile
LH effect in males
stimulates androgen synthesis
LH effect in females
ovulation, progesterone synthesis
FSH effect in males
FSH effect in females
follicle growth, estrogen synthesis
Which laboratory picture is characteristic of physiologic menopause?
low estrogen, high fsh, high lh
Hypothalamic TRH --> Pituitary TSH --> Thyroid T3/T4- -> negative feedback on hyptothalamus and pituitary // hypothalamic somatostatin also opposes TRH
sitmulates TSH and prolactin
When T3 is high/low, TRH receptors decrease and thus response of thyrotrope to TRH decreases and thus TSH increases/decreases
low and decreases