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89 Cards in this Set

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  • Back
How many hormones are produced by each cell type within the pituitary?
What area lies between the anterior and posterior pituitary?
Pars Intermedia - not important in humans
Which lobe of the pituitary is more vascular?
The anterior
What cell type sends neurons down into the posterior pituitary?
Magnocellular neurons in the hypothalamus
What bone does the pituitary sit on top of?
Sella Turcica
What are the 3 classes of hormones made by the Anterior Pituitary?
1. Glycoproteins
2. GH/Prolactin
3. POMC's
What are the 3 glycoprotein hormones?
What is the primary POMC?
What makes the glycoproteins similar?
Each has 2 subunits
-Alpha subunits are common
-Beta subunits give specificity
What is the target of TSH? What does it result in?
Thyroid - stimulates production and secretion of T3/T4
What are the targets of LH and FSH?
Testes and ovaries
What does FSH do in the ovaries?
-Stimulates follicular growth
-Stimulates estrogen secretion
What does FSH do in the testes?
-Promotes sperm maturation
What does LH do in the ovaries?
-Stimulates ovulation of ripe follicle
-Stimulates corpus luteum formation
-Stimulates synth/secretion of Estrogen / Progesterone from the corpus luteum
What does LH do in the testes?
Stimulates the Interstitial cells of Leydig to make/secrete Testosterone
What is the target of Growth Hormone?
Most tissues
What are the 4 effects of GH?
-Growth in stature/mass
-Production of IGF1
-Protein synthesis
-Inhibition of glucose/promotion of fat utilization
What is the target/effect of Prolactin?
Target: mammary glands
Effect: milk secretion
What is the target/effect of ACTH?
Target: adrenal cortex
Effect: synth/secretion of adrenal cortical hormones
What is the other hormone that is made by the POMC family?
How are ACTH and LPH made?
Both are made by one cell type, but the enzymes expressed in that cell determine the final product of post-translational processing.
What are the 2 ways that hormones act?
-Acutely -> Tropic
-Chronically -> Trophic
What does it mean to say a hormone has a trophic effect?
It continues to stimulate its target tissue in the longterm in order to prevent atrophy of the tissue
What will happen if there is too much chronic stimulation? What if there's not enough?
What are the landmarks at the front/back of the hypothalamus?
Front: optic chiasm
Back: mammillary bodies
What are the mammillary bodies involved in?
Limbic system
How long are the axons that extend from the hypothalamus to
-Anterior pituitary
-Posterior pituitary
Anterior = SHORT
Posterior = long
How many capillary plexuses are involved in the relationship of the hypothalamus to anterior pituitary?
2 - one in the hypothalamus, one in the anterior pituitary
What do we call this system of blood vessels?
A portal system
What are the vessels that run from the hypothalamic caps to the anterior pituitary caps?
Portal vessels
Why does this portal system exist?
So the hypothalamic short axons can release factors into the 1st capillary plexus, to be carried to the ant pit and cause secretion of its hormones.
What hypothalamic factor promotes secretion of the POMC hormones?
CRH - corticotropin releasing hormone
What hypothalamic factor promotes secretion of the gonadotropins?
What hypothalamic factor promotes secretion of Growth Hormone?
What is SRIF?
Somatotropin Release Inhibiting Factor; aka Somatostatin
What does SRIF do?
Inhibits release of growth hormone
What stimulates Prolactin secretion?
What inhibits Prolactin secretion?
Dopamine (Prl inhibiting Fx, PIF)
What are 2 effects of TRH?
Thyrotropin release hormone stimulates TSH and Prl release
What is the name for GH + Prl together?
What makes the Somatomammotropins unique from the other hormones?
They cause direct effects on their targets, rather than just secretion of more hormones to affect another target
What does Longloop inhibitory feedback mean?
A peripheral tissue product is what inhibits the pituitary of hypothalamus
What does Shortloop inhibitory feedback mean?
A product of the pituitary inhibits hypothalamic release
What is the general model for Hypothalamic-Pit-Target control?
1. Environmental fxs act on hypthalamus
2. Hypothal acts on Pituitary
3. Pituitary acts on target
4. Negative feedback
What is the HPA axis?
What are the environmental factors that act on the hypothalamus in the HPA axis? What part of the hypothal?
Higher brain centers act on the Paraventricular Nuclei (PVN) to cause CRH release
What does CRH do?
Stimulates ACTH release from anterior pit
What does ACTH do?
Stimulates the Adrenals to release cortisol
What does Cortisol do?
-Target effects
-Longloop Neg feedback to the pituitary and hypothal
What is the HPT axis?
Where are the TSH receptors in the thyroid?
On follicular cells
Which is the major thyroid hormone product of follicular cells?
T4 - Thyroxine
How is T4 transported in the blood?
Bound to TBG - thyroid binding globulin
Is Thyroxine very active?
No; it is a prohormone that is converted to T3 in the liver and tissues.
What are the main things that control pituitary release of TSH?
Circulating T3/T4 - NOT TRH
What is the function of TRH?
It changes the sensitivity of thyrotrophs in the pituitary to circulating T3/T4
What will happen to the HPT axis if the brain senses an increased need for T3/T4?
TRH release will increase, decreasing the sensitivity of the pituitary to T3/T4 so that it will less inhibited and able to release TSH
What will happen if T3/T4 are in excess?
TRH release will decrease, making the pituitary more sensitivity to T3/T4 so it doesn't release as much TSH.
What are the 2 hypothalamic factors that control Growth Hormone release from the pituit?
GHRH - stimulatory
Somatostatin - inhibitory
What is the target tissue and effect of GH?
The liver - production of IGF1
What is IGF1?
Insulin-like growth factor - it looks like insulin but is completely unrelated functionally.
What is another name for IGF1?
Somatomedin - mediates somatic growth.
What is the longloop feedback loop for GH release?
-Inhibits pit release of GH
-Stimulates hypothal release of Somatostatin (which inhibits GH)
What is the shortloop feedback loop for GH release?
Pituitary-released GH inhibits hypothalamic release of GHRH.
What is special about how Gonadotropin Releasing Hormone is released from hypothalamus?
3 Phases of the Menstrual cycle:
During the follicular phase what do LH/FSH stimulate the ovary to do?
Produce Estrogen and Inhibin
What do Estrogen/Inhibin do?
-Neg feedback to pituitary release of FSH/LH
-Estrogen stimulates its own release from the ovary (autocrine)
What happens to the effect of estrogen during MIDCYCLE?
It STIMULATES release of more FSH/LH from pituitary instead of inhibiting it!
What do we call the unusual way that Estrogen acts in midcycle of the menstrual phase?
Positive feedback
What are the 3 positive feedback loops in the menstrual cycle?
1. Estrogen stimulating LH/FSH release in midcycle
2. Parturition via Oxytocin stimulating cervix
3. Nursing induced Prl release
What happens in the Luteal phase?
Good old neg feedback
-Now ovary produces Est/Prog
-They inhibit release of FSH/LH
-Also inhibit GnRH release
What is the hypothalamic nucleus that releases GnRH?
Medial Preoptic nucleus
What is the nature of GnRH release?
What happens in men when GnRH is released?
It stimulates release of FSH/LH from pituitary, which stimulates Sertoli cells and Leydig cells
What is the effect of FSH stimulating Sertoli cells?
-Release of inhibin
What is the effect of LH stimulating Leydig cells?
-Testosterone release
What do we call the neg feedback of both inhibin and testosterone?
Parallel neg feedback
What is the ultimate exception to feedback loops in endocrinology?
PROLACTIN - there is no negative feedback; it's stimulus induced.
What stimulates prolactin release? How?
-Suckling stimulus
These inhibit the hypothalamus from releasing Dopamin
What happens dopamine release is inhibited?
The pituitary is able to release prolactin
Effect of prolactin
Milk synthesis
What is Parlodel?
A dopamine agonist
What is the effect of Parlodel?
Decreased prolactin release
What is Parlodel used to treat?
Macroadenoma - a prolactin secreting tumor
What is the most common type of invasion that causes hypopituitarism?
Pituitary tumors
What is Sheehan's syndrome?
An infarction due to hypertensive vessels during the increase in prolactin secretion after pregnancy - postpartum necrosis
What is an infilatrative cause of hypopituitarism?
Hemochromatosis - iron infiltrates the pituitary and reduces its production.
What is a very sad cause of head trauma that can cause hypopituitarism?
Shaken baby syndrome - reduces growth hormone