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The Hypothalamo-Pituitary-Adrenal Axis

The Hypothalamo-Pituitary-Adrenal Axis. Table 10.1 Factors Influencing Evaluation of Endocrine Function in Aging. Physiologic Metabolism Body Composition Nutrition Exercise Stress. Inter-endocrine Relations Secretory Rate Transport to target site. Hormone Metabolism  Activity

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The Hypothalamo-Pituitary-Adrenal Axis

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  1. The Hypothalamo-Pituitary-Adrenal Axis

  2. Table 10.1 Factors Influencing Evaluation of Endocrine Function in Aging Physiologic Metabolism Body Composition Nutrition Exercise Stress Inter-endocrine Relations Secretory Rate Transport to target site Hormone Metabolism  Activity T4  T3 T  DHT Number & Affinity Of Receptors

  3. Hypophysiotropic hormones CRH: corticotropic releasing hormone GHRH: growth hormone releasing hormone GHIH: growth hormone inhibitory hormone Somatostatin PRH: prolactin releasing hormone GnRH: gonadotropin releasing hormone TRH thyrotropin (TSH)-releasing hormone Pituitary Hormones ACTH: adrenocorticotropin hormone LH: lutenizing hormone FSH: follicle stimulating hormone PL: prolactin TSH: thyroid stimulating hormone GH: growth hormone **Please see Figures 10.7-10.9 in text** Figure 10.1

  4. Figure 10.2

  5. Figure 10.3 Diagram of a section of the adrenals illustrating the various zones and hormones

  6. Figure 10.6 Reminder CRH: corticotropic releasing hormone ACTH: adrenocorticotropic hormone

  7. Actions Of Glucocorticoids Actions of Adrenaline/Noradrenaline Target cellular

  8. Figure 10.5 Schematic diagram of corticosteroid action in target cell

  9. Gene expression & new protein synthesis • Relatively long latency of onset • Medium & long term cell program • Organization of cell networks for complex functions • Activation/repression of pre-existing cell proteins • Rapid onset of action • Rapid adaptation to changes in the milieu • Dynamic modifications of long term cell programs

  10. Figure 10.7 Diagrammatic representation of the anterior pituitary

  11. Figure 10.8 Diagrammatic representation of the posterior pituitary

  12. Changes with Aging in the Hypothalamo-Pituitary-Adrenal Axis No significant changes in healthy, non-stressed, elderly The few changes that occur are rapidly compensated for (e.g. decreased secretion of GCs from the adrenal cortex) but also less rapid metabolism in the liver & less urine excretion Therefore the circulating levels remain constant Also, normal ACTH & cortisol responses to CRH administration Some alterations of the circadian rhythm

  13. STRESS Cortisol, norepinephrine, and epinephrine

  14. Figure 10.4 Corticosterone titers in young (3-5 mo) and aged (24-28 mo) rats Old rats Young rats

  15. Exposure to Stress Generates: • Specific responses: vary with the stimulus (specialized responses) and generate different responses with each different stimulus. • Nonspecific responses: (also called non- specialized) are always the same • regardless of the stimulus • mediated through stimulation of neural, endocrine, and immune axis

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