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Lecture 20
• SmartSite:
– Lecture 20 Notes
• Announcements:
– None
• Reading (Recommended):
– Relevant por3ons Chapter 4 & 18
• Review – Endocrinology Introduc3on
• Endocrinology – Introduc3on
– Neuroendocrine
– Growth Hormone
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REV: Hormone ClassificaBon
Table 4-­‐4, pg. 122
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(More) Mechanism of AcBon of Hydrophilic Hormones Fig. 4-­‐25, pg. 126
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Signal AmplificaBon
Fig. 4-­‐27, pg. 127
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Mechanism of AcBon of Lipophilic Hormones
• Effects are generally slower onset, longer lasBng than effects via membrane receptors
• Examples:
– Estrogen induces genes inducing growth of uterus, mammary glands
– Thyroid hormone induces genes involved in cerebellar Purkinje cell differenBaBon, axon myelinaBon
Fig. 4-­‐28, pg. 128
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Hormone Influence at Target Cell
• Hormone can influence acBvity of another hormone at given target cell in one of three ways
– Permissiveness
• One hormone must be present in adequate amounts for full exerBon of another hormone’s effect • OWen by increasing second hormone’s receptors
– Synergism
• Occurs when acBons of several hormones are complimentary
• Combined effect is greater than the sum of their separate effects
– Antagonism
• Reduces effecBveness of second hormone
• OWen by decreasing the second hormone’s receptors, or down-­‐
stream signaling
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Causes of Endocrine Disorders
Table 18-­‐1, pg. 661
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Neuroendocrine
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Pituitary Gland
• Hypophysis
• Small gland located in bony cavity just below hypothalamus
– Thin stalk connects pituitary gland to hypothalamus
• Consists of two anatomically and funcBonally disBnct lobes
– Posterior pituitary (neurohypophysis)
• Composed of nervous Bssue
– Anterior pituitary (adenohypophysis)
• Consists of glandular epithelial Bssue
Fig. 18-­‐3, pg. 662
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Pituitary Gland
• Release of hormones from both anterior and posterior pituitary is controlled by hypothalamus
• Posterior pituitary
– Along with hypothalamus forms neuroendocrine system
– Does not actually produce any hormones
– Stores and releases two small pepBde hormones
• Vasopressin
– Conserves water during urine formaBon
• Oxytocin – SBmulates uterine contracBon during childbirth and milk ejecBon during breast-­‐feeding
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Hypothalamus & Posterior Pituitary
Fig. 18-­‐4, pg. 663
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Anterior Pituitary
• Anterior Pituitary
• Secretes six different pepBde hormones that it produces itself
– Tropic hormones
• Thyroid-­‐sBmulaBng hormone (TSH)
– SBmulates secreBon of thyroid hormone
• AdrenocorBcotropic hormone (ACTH)
– SBmulates secreBon of corBsol by adrenal cortex
• Follicle-­‐sBmulaBng hormone (FSH)
– In females, sBmulates growth and development of ovarian follicles; promotes secreBon of estrogen by ovaries
– In males, required for sperm producBon
• Luteinizing hormone (LH)
– In females, responsible for ovulaBon and luteinizaBon; regulates ovarian secreBon of female sex hormones
– In males, sBmulates testosterone secreBon
• Growth hormone (GH)
– Primary hormone responsible for regulaBng overall body growth; important in intermediary metabolism
– Not a tropic hormone
• ProlacBn (PRL)
– Enhances breast development and milk producBon in females
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Anterior Pituitary Hormones
Fig. 18-­‐5, pg. 667
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Vascular Link Between the Hypothalamus and Anterior Pituitary
Median eminence
Fig. 18-­‐7, pg. 671
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Major Hypophysiotropic Hormones
• SecreBon of each anterior pituitary hormone is sBmulated or inhibited by one or more hypothalamic hypophysiotropic hormones
Table 18-­‐4, pg. 669
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NegaBve Feedback in Endocrine Control
• Anterior pituitary hormone secreBon controlled by:
– Hypothalamic releasing and inhibiBng hormones
– Feedback by target-­‐
gland hormones
Fig. 18-­‐6, pg. 670
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Endocrine Control of Growth
• Growth depends on growth hormone but is influenced by other factors as well
– GeneBc determinaBon of an individual’s maximum growth capacity
– An adequate diet
– Freedom from chronic disease and stressful environmental condiBons
– Normal levels of growth-­‐influencing hormones
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Growth Rate • Not conBnuous
• Factors responsible for promoBng growth are not the same throughout growth period
• Fetal growth
– Promoted largely by hormones from placenta
– GH plays no role in fetal development
• Postnatal growth spurt
– Displayed during first two years of life
• Pubertal growth spurt
– Occurs during adolescence
Fig. 18-­‐8, pg. 672
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Growth Hormone
•
Primarily promotes growth indirectly by sBmulaBng liver’s producBon of somatomedins
– Primary somatomedin is insulin-­‐
like growth factor (IGF-­‐1)
• Acts directly on bone and soW Bssues to bring about most growth-­‐promoBng acBons
• SBmulates protein synthesis, cell division, and lengthening and thickening of bones
•
Exerts metabolic effects not related to growth
– Increases faey acid levels in blood by enhancing breakdown of triglyceride fat stored in adipose Bssue
– Increases blood glucose levels by decreasing glucose uptake by muscles
Fig. 18-­‐10, pg. 676
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Growth
• Other hormones besides growth hormone are essenBal for normal growth
– Thyroid hormone
• Growth severely stunted in hypothyroid children
• HypersecreBon does not cause excessive growth
– Insulin
• Deficiency oWen blocks growth
• Hyperinsulinism oWen spurs excessive growth
– Androgens
• Play role in pubertal growth spurt, sBmulate protein synthesis in many organs
• Effects depend on presence of GH
– Estrogens • Effects of estrogen on growth prior to bone maturaBon are not well understood poorly
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