Endocrinology 3 Flashcards
Describe the anatomical organization of the hypothalamus and the major hypothalamic nuclei associated with each hypothalamic-releasing hormone.
Slide 7, 10
On Slide 6, label tags 1-5.
- Cerebral peduncle
- Mammillary bodies
- Hypothalamus
- Optic Nerve
- Olfactory Tract
Describe the discrete nuclei into which the hypothalamus is divided.
PVN = Paraventricular Nucleus POA = Preoptic Nucleus ARC = Arcuate Nucleus SCN = Suprachiasmatic Nucleus SON = Supraoptic Nucleus
What is the medial eminence? What is its significance?
ME = Medial Eminence
Floor of hypothalamus
Convergence point for axons
Describe the hypothalamic functions and where they are localized.
Sleep (SCN) Feeding behavior/satiety (ARC) Thirst (PVN) Reproduction (POA) Circadian rhythms (SCN) Mood/emotion/stress (PVN/ARC) Body temperature (POA) Blood pressure (PVN)
Where are the following localized?
Sleep Feeding behavior/satiety Thirst Reproduction Circadian rhythms Mood/emotion/stress Body temperature Blood pressure
Sleep (SCN) Feeding behavior/satiety (ARC) Thirst (PVN) Reproduction (POA) Circadian rhythms (SCN) Mood/emotion/stress (PVN/ARC) Body temperature (POA) Blood pressure (PVN)
For the following hormone describe the brain nuclei, pituitary target, and function:
GnRH (peptide)
GnIH (inhibitor)
Brain nuclei - Scattered – POA has majority
Pituitary target- Gonadotropes – FSH, LH
Function - Reproduction
For the following hormone describe the brain nuclei, pituitary target, and function:
CRH (peptide)
Brain nuclei - Paraventricular (PVN) (parvocellular)
Pituitary target- Corticotrope - ACTH
Function - Glucocorticoids – pleiotropic effects
For the following hormone describe the brain nuclei, pituitary target, and function:
TRH (peptide)
Brain nuclei - PVN
Pituitary target- Thyrotrope - TSH
Function - Thyroid hormone – pleiotropic effects
For the following hormone describe the brain nuclei, pituitary target, and function:
GHRH (peptide)
Brain nuclei - Arcuate nucleus
Pituitary target- Somatotrope - GH
Function - growth and development
For the following hormone describe the brain nuclei, pituitary target, and function:
Somatostatin
(GHRH inhibitor)
Brain nuclei - Periventricular (PeVN)
Pituitary target- Somatotrope
Function - Inhibits GH
For the following hormone describe the brain nuclei, pituitary target, and function:
Dopamine (amine)
Brain nuclei - Arcuate nucleus
Pituitary target- Lactotrope - prolactin
Function - Milk production
Which hormones have IP3/DAG/PKC as their second messengers? About how big are they?
TRH- 3 aa
GnRH- 10 aa
Which hormones have cAMP as their second messengers?
CRH- 41 aa
GHRH- 44aa
GHIH (somatostatin)- 14aa
Discuss the structure, function, receptors, and intracellular signaling pathways for GnRH.
GnRH is peptide hormone so signal peptide here, then 10aa GnRH then GAP which is co-peptide
whole things is prepro-GnRH
then cleaved
and released
will activate its G membrane protein receptor
slide 15
Explain the GnRH deficiency associated with Kallman Syndrome.
Rare genetic disease (1:8000 men/1:40,000 women)
GnRH neurons fail to enter CNS
Characterized by reproductive failure and anosmia
Heritable: X-linked = Kal1, autosomal = Kal2
Describe GONADOTROPIN-RELEASING HORMONE (GnRH – LHRH):
Where are cell bodies?
Where is largest concentration?
Where do axons extend toward?
What type of hormone?
Cell bodies scattered throughout forebrain
Relatively few (approx 1500-2000) in humans (compared to 100 billion total neurons)
Largest concentration in POA
Very long axons extend towards median eminence
GnRH is a decapeptide (10 aa)
Highly conserved among vertebrates
Diagram the vascular connections between the hypothalamus and pituitary.
Slide 19
superior and inferior hypophysial arteries
hypophysial vein and portal vein
What is the hypophysial portal system?
How was it discovered?
Vascular connection between the hypothalamus and pituitary gland.
When pituitaries were transplanted in other locations they stopped secreting hormones.
Once re-implanted they only worked if vascular system was re-established.
Slide 18
How is GnRH pulsatility measured?
measured from portal vein
What do the following release?
Lactotroph mammosomatroph somatotroph thyrotroph gonadotroph corticotroph
Lactotroph- Prolactin
mammosomatroph- prolactin and growth hormone
somatotroph- growth hormone
thyrotroph- thyrotropin
gonadotroph- LH, FSH
corticotroph- corticotropin
Explain the importance of hypothalamic and pituitary hormone pulsatility.
Slide 23-26
Pulse frequency determines which gonadotropin subunit is released
Explain the difference between the tuberoinfundibular system and the neurohypophysial tract.
Tuberoinfundibular System - comprises all neurons that send axonal projections to the median eminence. Hormones target the anterior pituitary through the capillary system (endocrine).
- Neurohypophysial Tract – comprises neurons whose axons terminate in the posterior pituitary.
Compare and contrast the anatomical organization of the anterior and posterior pituitary gland and identify which hypothalamic hormones target each lobe.
POSTERIOR PITUITARY – NEUROHYPOPHYSIS
Axons from magnocellular neurons terminate in neurohypophysis (“neurohypophysial tract”).
Blood supply from inferior hypophysial artery – has its own capillary bed.
Major hormones: Arginine vasopressin (AVP) and oxytocin (OXY).
Slide 34
ANTERIOR PITUITARY – ADENOHYPOPHYSIS Median eminence (ME) is the interface for all hypophysiotrophic hormones.
ME lies outside the blood brain barrier and forms the floor of the 3rd ventricle.
Identify important histological features that distinguish the anterior and posterior lobes of the pituitary.
Anterior Pituitary
Pars distalis (90%)
Pars tuberalis
Pars intermedia
Posterior pituitary
Pars nervosa
Infundibulum (stalk)
Adenohypophysis (anterior pituitary)
-Glandular tissue: Cords of epithelial cells
Neurohypophysis (posterior pituitary)
-Neural tissue: Terminal axons and glial cells
In pars nervosa, where do axons terminate?
near fenestrated capillaries
Where are pituicytes located?
pars nervosa of posterior pituitary
What are Herring bodies?
Herring bodies = dilations of unmyelinated axons near their terminals. Contain vesicles of either AVP or Oxytocin plus a binding protein, neurophysin.
What is neurophysin?
Herring bodies = dilations of unmyelinated axons near their terminals. Contain vesicles of either AVP or Oxytocin plus a binding protein, neurophysin.
Describe the 5 major cell types in the anterior pituitary and explain which cells are responsible for synthesizing and secreting LH/FSH, TSH, GH, ACTH, and Prolactin.
Where in the pituitary are these clustered? DRAW.
Acidophils – (40%) most abundant
Somatotrophs = growth hormone (GH)
Lactotrophs = prolactin (lactation)
Basophils (10%)
Corticotrophs = ACTH (stress)
Gonadotrophs = LH/FSH (reproduction)
Thyrotrophs = thyroid stimulating hormone (TSH)
Chromophobes (50%)
Paracrine actions
Slide 40
Draw quick pathway from hypothalamus (magnocellular neuron) and hypothalamus (parvicellular neuron).
Slide 41
What is important to keep in mind when taking blood samples to evaluate endocrine disease?
Most pituitary hormones have a circadian rhythm
Important consideration when taking blood samples to evaluate endocrine disease
Slide 42
Which two hormones are not regulated by HP endocrine axes?
Arginine vasopressin (AVP) and oxytocin (OXY).
Axons from magnocellular neurons terminate in neurohypophysis (“neurohypophysial tract”).
Slide 33
(these aren’t regulated by HP endocrine axes bc ones regulated by those dump their contents into portal system)
Describe the anterior and posterior pituitary blood supply.
Pituitary Blood Supply. Superior hypophysial artery gives rise to capillary plexus = “portal plexus” in anterior pituitary. Breaks into a primary capillary plexus within the median eminence. Then drains into hypophyseal portal veins and the secondary capillary plexus located in pars distalis.
Inferior hypophysial artery supplies the posterior pituitary
