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Stress (cont.)

Stress (cont.). During stress, the priorities of the secretions of the hypothalamo-pituitary peripheral-endocrine axes are shifted in favor of the hypothalamo-pituitary-adrenocortical (HPA) axis. During stress: HPA GHRH GH GnRH FSH LH. Hypothalmo-Pituitary-Thyroid System.

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Stress (cont.)

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  1. Stress (cont.)

  2. During stress, the priorities of the secretions of the hypothalamo-pituitary peripheral-endocrine axes are shifted in favor of the hypothalamo-pituitary-adrenocortical (HPA) axis. During stress: HPA GHRH GH GnRH FSH LH

  3. Hypothalmo-Pituitary-Thyroid System

  4. Figure 13-1: Diagrammatic representation of the thyroid gland

  5. Figure 13-2

  6. Table 13.3Major Actions of Thyroid Hormones • Calorigenesis • Metabolism • Brain maturation • Behavior • Growth & development

  7. 3, 5, 3’, 5’ Tetraiodothyronine (thyroxine, T4) 3, 5, 3’ Triiodothyroine (T3)

  8. Table 13-2: Some MORPHOLOGIC Changes • in the Thyroid Gland with Aging FOLLICLES: - Are distended - Change in color - Epithelium flattened w/ reduced secretion Increased connective tissue; Fibrosis Atherosclerotic changes Fewer mitoses

  9. in antithyroid antibodies, present even in the absence of manifestations of hypothyroidism TSH levels in 10% of the elderly, associated circulating T3 levels but generally within the normal (lower) range peripheral conversion of T4 to T3 • Table 13-2 (con’t.): Some SECRETORY Changes • in the Thyroid Gland with Aging Simultaneously decreased secretion and metabolic clearance of T4 with resulting essentially normal levels Failure of up-regulation of T3 nuclear receptors

  10. Table 13-1: Some Critical Aspects of Thyroid Hormone Regulation Major source of circulating T3 from peripheral deiodination of T4 (NOT from thyroid gland secretion) The negative feedback at the pituitary anterior lobe is mainly through T4 (taken from circulation & converted into T3) The peripheral deiodination of T4 depends on the physiological state of the organism. It allows an autonomy of response of the tissues to the hormones. Deiodination can convert T4 (a less biologically active hormone) to T3 (a more active hormone). This conversion depends on the activity of the various deiodinating enzymes.

  11. Figure 13-4

  12. Basal Metabolic Rate from birth to 70 years old Basal Metabolic Rate

  13. Table 13-5 In the Elderly, • Thermoregulatory Insufficiency • Results from: • heat production, • body mass, • muscle activity, • shivering, • sweating response, • vasomotor responses, • temperature perception.

  14. Table 13-6 Autoimmune Diseases of the Thyroid Gland

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