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