1-27 Hypothalamus & Pituitary DSA Flashcards
What are the 7 hormones of the anterior pituitary?
TSH FSH LH ACTH MSH Growth Hormone Prolactin
What is the target/action of TSH?
Thyroid Stimulating Hormone
Stimulates synthesis and secretion of thyroid hormones
What is the target/action of FSH?
Follicle Stimulating Hormone
Stimulates sperm maturation in Sertoli cells of testes
Stimulates follicular development and estrogen synthesis in ovaries
What is the target/action of LH?
Luteinizing Hormone
Stimulates testosterone synthesis in Leydig cells of testes
Stimulates ovulation, formation of corpus luteum, estrogen, and progesterone synthesis in ovaries
What is the target/action of growth hormone?
Stimulates protein synthesis and overall growth
What is the target/action of prolactin?
Stimulates milk production and secretion in breasts
What is the target/action of ACTH?
Stimulates synthesis and secretion of adrenal cortical hormones - cortisol, androgens, and aldosterone
What is the target/actions of MSH?
Stimulates melanin synthesis
What are the hormones released by the posterior pituitary?
Oxytocin
ADH
What is the target/actions of oxytocin?
Stimulates milk ejection from the breasts and uterine contractions
(birth and milk)
What is the target/actions of ADH?
Vasopressin or antidiuretic hormone
Stimulates water reabsorption in principal cells of collecting ducts and constriction of arterioles
What is the difference between the anterior and posterior pituitary gland in terms of relationship to the hypothalamus?
Anterior:
Hypothalamus sends releasing/anti-releasing hormones to ant. pit. via hypothalamical-hypophysial portal vessels
Ant. pit. then releases hormones to target tissues
Posterior:
Hypothalamus synapses on post. pit and triggers release of neuropeptides ADH or oxytocin
What is the difference between the hormones released from anterior or posterior pituitary? (Hint: think general classification, not specific hormones.)
Post pit. - releases neuropeptides
Ant. pit. - releases mostly trophic peptide hormones, some of which act directly on glands to induce further hormone release, or act on target tissues directly
What are the differences in how hormones are released from anterior and posterior pituitary glands?
Anterior
released in response to hormone-releasing hormones derived from the hypothalamus
Posterior
originate in the hypothalamus and are transported down neurons to the posterior pituitary for release
How is the structure-function relationship different between anterior and posterior pituitary in regards to the hypothalamus?
Anterior - connected to hypothalamus via infundibulum and portal system
Posterior - connected directly to hypothalamus via neurons
How is the blood flow different to each region of the pituitary gland?
Anterior:
linked via hypothalamic-hypophysial portal blood vessels
- provides most of the blood supply
- hypothalamic hormones are delivered to ant. pit. directly and in high concentrations
- hypothalamic hormones are not in high concentrations in systemic circulation
Posterior
- not important enough to mention in the text, apparently
What are the hormones that are released by the hypothalamus? What are their target cells?
GhRH
- growth hormone releasing hormone
- works on somatotrophs
TRH
- thyrotropin releasing hormone
- works on thyrotrophs
PIF
- Dopamine/prolactin inhibiting factor
- works on lactotrophs
CRH
- Corticotropin releasing hormone
- works on corticotrophs
SRIF
- Somatostatin/somatotropin release-inhibiting factor
Describe the stimulatory factors for hypothalamic regulation of GH release from somatotrophs.
GHRH release from hypothalamus is stimulatory to GH release from ant. pit.
Describe the inhibitory factors for hypothalamic regulation of GH release from gonadotrophs.
Somatostatin/somatotropin release inhibiting factor is inhibitory to GH
What factors stimulate GH release?
Decreased glucose conc decreased FFa conc arginine fasting/starvation puberty hormones exercise stress Stage 3 and 4 sleep alpha adrenergic agonists
What factors inhibit GH release?
Increased glucose conc Increased FFA conc obesity senescence somatostatin somatomedins GH beta adrenergic agonists pregnancy
What are the patterns of GH release?
Pulsatile
- 1 burst ~2 hours
- largest within 1 hour of falling asleep
What are the patterns of GH release over a lifetime?
Increases steadily from birth into early childhood
- stabilizes
Boost in puberty
- estrogen/testosterone
- responsible for growth spurt
Declines to steady level afterward
- lowest level in senescence
What is the metabolic action of GH in relationship to IGF-1? What is it’s effect on insulin levels?
GH promotes release of IGF-1/somatomedin from liver
- IGF-1 causes feedback inhibition
Causes:
- insulin resistance (diabetogenic effect)
- increased protein synthesis and organ growth
- increased linear growth
Define how the pattern of GnRH determines FSH and LH secretion .
Pulsatile release of GnRH necessary for LH & FSH release
Frequency ofGnRH pulse determines LH or FSH release
Estrogen, testosterone, and inhibins feed back to regulate GnRH release
Describe the production and release of prolactin from the anterior pituitary.
Stimulatory for secretion: pregnancy breast feeding stress dopamine antagonists TRH
PRL stimulates dopamine synthesis, which inhibits ant pit and PRL release
What are inhibitory factors for prolactin?
Inhibitory: dopamine dopamine agonists: - bromocriptine - somatostatin
Describe the production and release of oxytocin from the posterior pituitary.
Synthesized in cell bodies of paraventricular nuclei
- initially created as preprohormone
- pre- cleaved in golgi
- packaged in vesicles
- travel down axon
- released when AP triggers Ca++ release
What is the synthesis and release of ADH?
Secreted by post. pit in response to increase in serum osmolarity
Synthesis is similar to oxytocin, mostly synthesized by supraoptic nuclei
What stimulates release of ADH?
Increased serum osmolarity decreased ECH volume Ang II pain nausea hypoglycemia nicotine opiates antineoplastic drugs
What inhibits release of ADH?
Decreased serum osmolarity
Ethanol
alpha adrenergic agonists
ANP
What are the actions of ADH on the vasculature and kidney?
Acts on principle cells of late distal tubules and collecting duct to increase water reabsorption
Contracts vascular smooth muscle
- via V receptor coupled to phospholipase C on a Gq protein
- 2nd messenger: Ip/Ca++
- increases total peripheral resistance
Where are the receptors for ADH located? How are they different:
Principle cells:
V receptor coupled to Gs protein and adenylyl cyclase
- cAMP as 2nd messenger
Vascular smooth muscle:
V receptor coupled to Gq protein with phospholipase C
- Ip/Ca++ as 2nd messenger
How are the clinical features of central diabetes insipidus related to ADH?
Failure of post pit to secrete ADH
- circulating ADH low
- collecting ducts impermeable to water
- urine can’t be concentrated
- serum osmolarity increases
How are the clinical features of nephrogenic diabetes insipidus related to ADH?
Principle cells unresponsive to ADH
- circulating ADH high
- collecting ducts impermeable to water
- urine can’t be concentrated
- serum osmolarity increases
What is SIADH?
Excess ADH secreted from autonomous/neoplastic site
- high ADH causes excess reabsorption of water
- dilution of body fluids
