Endocrine Physiology Flashcards
Transport of Steroid Hormones
Bound to proteins
Active form of Steroid Hormones
Free & Unbound Form
Main site of inactivation of Hormones
Liver
Mechanism for removal of hormones
Kidneys, Liver
Onset of hormonal effects
Seconds to months
Number of hormones receptors
Variable
Minimum amount of hormone to produce effect
1 picogram per ml
Epi + NE effects on the heart
Additive effects (synergy)
FSH & Testosterone on spermatogenesis
Complementary effects (synergy)
Cortisol on NE and Epi in blood vessels; T3 on Epi in Lipolysis
Permissive effects
Estrogen blocking Prolactin effect on breast during pregnancy
Antagonistic effects
2 ways to regulate hormone effects
Hormone secretionHormone receptors
Self-limiting; More common; Hormone has biologic actions that directly or indirectly, inhibit further secretion of the hormone
Negative feedback
Self-augmenting; Rare, exploding; Hormone has biologic actions that directly or indirectly, stimulate further secretion of the hormone
Positive feedback
Hormone feeds back all the way to HPA
Long-loop feedback
Hormone from Pituitary feeds back to the Hypothalamus
Short-loop feedback
Hypothalamic hormone feeds back on its own secretion
Ultra-short-loop feedback
Example of negative feedback that does not utilize HPA
Insulin
Examples of Positive Feedback
Estrogen-induced LH & FSH surge, Oxytocin during labor and lactation
Decrease in receptor number or receptor affinity
Down-regulation of receptors
Increase in receptor number or receptor affinity
Up-regulation of receptors
Lies in sella turcica; Connected to the median eminence of Hypothalamus via Pituitary/Hypophysial stalk
Pituitary Gland
Transmit hypothalamic hormones to the pituitary without passing through the systemic circulation
Hypothalamic-Hypophysial Portal Blood Vessels
Adenohypophysis; Derived from oral ectoderm (Rathke’s Pouch); With Basophilic and Acidophilic Cells
Anterior Pituitary
Neurohypophysis; Derived from neural ectoderm (neural outgrowth of hypothalamus); With Pituicytes
Posterior Pituitary
From Basophilic Cells
FSHLHACTHTSHMSH
From Acidophilic Cells
GHProlactin
From Pituicytes
VasopressinOxytocin
If the pituitary stalk is damaged, all anterior pituitary hormones would decrease, EXCEPT
Prolactin
In terms of number, what are the top 2 cells in the anterior pituitary?
Somatotropes (40%) Corticotropes (20%)
What are the 3 families of hormones in the anterior pituitary?
TSH, LH, FSHMSH, ACTHGH, Prolactin
Both catabolic and anabolic; Released in pulsatile fashion (every 2 hours); Nocturnal peak: 1 hour after Stage 3 or 4 sleep
Growth Hormone
Growth Hormone
Somatotropin
Stops Growth Hormone
Somatostatin
IGF
Somatomedin
Direct Actions of GH
Increases blood glucose levels (Diabetogenic Effect)Increased protein deposition in muscles and other tissuesRequires adequate insulin and carbohydrate concentrateIncreased lipolysisIncreased Insulin-like Growth Factor (IGF) productionPossible anti-aging effects
Indirect Actions of GH
Increases Bone Length and Bone thicknessIncreases protein synthesis in muscles and most organs
Secretion of GH INCREASED
Starvation HypoglycemiaLow fatty acid levelsExerciseExcitementTraumaTestosteroneEstrogenGHRHDeep sleep
Secretion of GH DECREASED
HyperglycemiaHigh fatty acids levelsAging ObesitySomatostatin/SRIF (Somatostatin-release Inhibiting Hormone)Exogenous GHSomatomedins
Secretion of GH requires
Normal plasma levels of thyroid hormones
Decreased GH, MCC of Dwarfism, Defect in FGF receptor 3
Achondroplasia (AD)
Increased GH, With skeletal deformities (large hands, feet, membranous bones)
Acromegaly
Increased GH, Without skeletal deformities, symmetrical
Gigantism
Stimulates milk production (lactogenesis); Inhibits ovulation or spermatogenesis; Stimulates breast development during puberty and pregnancy
Prolactin
Prolactin Stimulation
PregnancyBreast feedingSleepStressTRHDopamine antagonists
Prolactin Inhibition
DopamineBromocriptineSomatostatinProlactin (negative feedback)
Aka ADH or AVP; Secreted by supraoptic nuclei of the hypothalamus; Responds to ECF changes detected by osmoreceptors in the Organum Vasculosum
Vasopressin
Most potent stimulus for Vasopressin
Increases plasma osmolality
Effects of Vasopressin
Increases water permeability via insertion of AQP2 in the late distal tubule and collecting duct (V2 receptors); Acts within 5-10 minsPeripheral vasoconstriction (V1 receptors)
Urine volume in Central Diabetes Insipidus
High