Flashcards in Pituitary Physiology Deck (28)
What are the origins of the Anterior and posterior pituitary?
Anterior: Oropharynx ectoderm (Rathke's pouch)
Posterior: Neuroectoderm just below third ventricle
What are activating transcription factors in pituitary development? What happens with inactivating mutations
PROP-1: inactivation--> No FSH, LH, PRL, GH, TSH
Pit-1: responsible for somatotropes, lactotropes, thyrotropes
What is function of GH?
Stimulates IGF-1 secretion-->Anabolic function
Stimulates lipid/CHO metabolism
What is function of TSH?
Stimulates secretion of thyroid hormones-->regulates thyroid cell proliferation/survival
Function of ACTH?
Stimulates synthesis/secretion of corticotropins in adrenal cortex
Function of PRL?
milk production, inhibits GnRH (suppressing LH/FSH)
Function of LH?
Female: Induces ovulation and progesterone synthesis
Male: gametogenesis, leydig cells, synthesis/secretion of testosterone
Function of FSH?
Females: Stimulate estrogen synthesis, promote follicular growth
Males: promoters spermatogenesis
What are the rhythms in endocrinology? Describe them and give example
Circadian rhythms: daily pattern; most endocrine functions (i.e cortisol)
Ultradian rhythms: bursts of hormone secretion that can be superimposed on circadian rhythms (i.e gonadotropins)
Describe HPA Axis in relation to corticotropins
Hypothalamus secretes Corticotropin Releasing Hormone (CRH)
CRH stimulates ACTH produciton in Anterior pituitary
ACTH stimulates cortisol secretion in adrenal gland
What are extra-adrenal actions of ACTH? (2)
Stimulate lipolysis and increase skin pigmentation
What are stimuli for ACTH? (6)
CRH, stress, hypoglycemia, anxiety, depression, a/ß-adrenergic agonists
Explain pattern of ACTH Release: Circadian? Ultradian?
Diurnal pattern: peaks just before awakening
Also has pulsatility
Describe the HPA Axis for GH
Hypothalamus secretes GHRH (stimulatory) OR somatostatin (inhibitory factors)
Anterior pituitary secretes GH
Liver secretes IGF1, which provides negative feedback
Stimulatory factor for somatotropes
GHRH: What is stimulated by? (3) What inhibits it (2)
Stimulated by: hypoglycemia, dietary protein, exercise
Inhibited by: IGF-1, GH
What is function of Somatostatin?
Inhibits GH, TSH, PRL, glucagon, insulin
What are FDA analogs of Somatostatin? (2)
Octreotide and lantreotide
Describe HPA Axis for PRL
Hypothalamus secretes prolactin releasing factor (PRF) OR inhibitory dopamine
Anterior Pituitary secretes PRL (neg feedback hypothalamus)
Prolactin stimulates milk production
What are stimulating factors for PRL? (6)
What are inhibiting factors?
Stimulators: breast stimulation, stress, estrogen, sleep, dopamine antagonists, TRH
Inhibitors: DA, DA agonists
What is effect of prolactin on LH/FSH secretion?
It negatively regulates HPG axis-->Decreases secretion of LH/FSH
Describe HPG Axis
Hypothalamus releases GnRH (pulsatility/frequency important)
Pituitary secretes FSH/LH (pulsatile)
Ovary/Testis stimulated and weird things going on in terms of feedback (i.e low vs. high estrogen)
Males: stimulate testosterone synthesis
Females: induces ovulation, stimulates progesterone synthesis
Male: facilitates sperm production
Female: Stimulates estrogen synthesis, promotes follicular growth
Describe Hypothalamic-Pituitary-Thyroid Axis
Hypothalamus stimulates TRH (stimulatory) or Somatostatin (inhibitory)
Ant Pituitary secretes TSH
Thyroid stimulation increases T4/T3 output (provides negative feedback via TRH receptors on pituitary)
In which axis is hypothalamic regulation primarily inhibitory?
Which are important inhibitory hypothalamic factors (2)