Endocrinology

1. Endocrinology A System of Blood-Born Chemical Messengers

2. Endocrine System • What is an endocrine gland?Tissue that secretes a chemical messenger directly into the blood stream. • How does it differ from an exocrine gland?Exocrine glands have ducts (internal tubes) that store secretions and deliver the secretion to a distinct target. • What is a hormone? (traditional definition)A chemical messenger secreted by a tissue and acting on a distant target tissue. • What is a target tissue?A tissue that has a receptor molecule that can bind with, and retain the hormone. • What does a hormone receptor do?After binding with a hormone, the receptor initiates a biochemical change in the target tissue at the membrane, the cytoplasm or the nucleus.

3. Melatonin: Biorhythms Pineal Gland 11 different hormones that are direct acting or tropic hormones Pituitary Parathormone – regulates blood calcium Parathyroid Thyroid hormone – regulates metabolic rate; calcitonin - regulates blood calcium Thyroid Thymus Thymosin – important for development of The immune system. Epinephrine and norepinephrine Regulate response to short-term stress Steroids regulate glucose, fat, and mineral Levels in blood Adrenal Gland Pancreas Insulin and Glucagon - both help Regulate the use or storage of glucose Ovary Ovaries and testes produce various steroid hormones that regulate reproduction and cause sex differentiation. Testes

4. Classes of Hormones • Steroids (estrogen, testosterone, cortisol)All synthesized from cholesterolAll are lipid soluble and may pass through membranes • Proteins (insulin, glucagon, prolactin)Large molecules, generally water soluble • Peptides and amino acid (thyroid hormone, hormones from the posterior pituitary) • Prostaglandins (made from membrane lipids) – usually function as very short range hormones, involved with blood clotting, regulation of reproductive system.

5. How Does Endocrine Control Differ From Nervous Control? • Nervous System • uses neurons to reach target tissue • very fast • short duration • typically controls muscles and glands • Endocrine System • uses hormones and blood • stream • slower onset (minutes-days) • longer duration (hours- • months) • Typically regulates metabolism, growth, reproduction

6. Steroid and Thyroid Receptor Systems

7. Protein and Peptide Receptor Systems

8. Endocrine Pancreas - Islet Cells Regulation of Blood Glucose Alpha cells secrete glucagon stimulates the breakdown of glycogen to glucose at liver and muscle stimulates the production of glucose from protein (gluconeogenesis) Beta Cells secrete insulin stimulates uptake of glucose from blood into muscle, epithelium and adipose tissue stimulates the formation of glycogen in muscle and liver.

9. Stimulates formation ofglycogen from glucoseat liver and muscle Promotes uptake of glucoseat muscle, adipose and epithelial tissues Insulin Blood GlucoseDecreases a When bloodglucose is high b Pancreas Inhibits insulinsecretion Inhibits glucagon secretion Blood GlucoseIncreases When blood Glucose is low Stimulates change ofglycogen into glucoseat liver and muscle Glucagon Stimulates gluconeogenesis

10. Diabetes Mellitus – high blood glucose • Type I: - patient produces very little, or no insulin - glucose levels remain high following meals - liver and muscle do not store glycogen - patient rapidly loses weight (wasting disease) - autoimmune disease - requires daily insulin injections • Type II: - patient produces normal levels (or even high) levels of insulin, but tissues do not respond. - glucose levels remain high following meals - enough insulin functions so that glycogen and lipids are stored, but blood glucose remains high. - usually due to obesity - may be “cured” through diet and exercise

11. Consequences of High Blood Glucose • High Glucose levels are toxic to small blood vessels. • Diabetic retinopathy • Kidney failure (need of dialysis) • Neuropathy • Loss of peripheral blood flow (gangrene and amputations)

13. Hypothalamus Neurosecretory cells Infundibulum Posterior Pituitary Anterior Pituitary Antidiuertic Hormone Kidney (water retention) Oxytocin Mammary (milk ejection) Uterus

14. Neurosecretory cells RH RH Releasing hormone Tropic or Direct Acting Hormone

15. Mini-Review • What type of cell produces oxytocin and antidiuretic hormone? • What are the target tissues for oxytocin and antidiuretic hormone? • What physiological effects do they have? • What type of cell produces releasing hormones? • What is the target tissue for a releasing hormone and how does the releasing hormone get there? • What happens when a releasing hormone binds to receptors on its target tissue? • What do tropic hormones do? • What do direct acting hormones do?

16. Thyroid Hormone and Regulation of Metabolism • Thyroid Hormone is made from the amino acid called tyrosine. It is the only hormone that requires iodine, and so small amounts of iodine are required in the diet. Two different forms T3 and T4 • Thyroid hormone is stored in the thyroid gland in chambers called follicles – attached to a protein called thyroglobulin. • Goiter: enlargement of the thyroid gland.

18. Physiological Effects of Thyroid Hormone • Development of the nervous system; effectssensitivity of the nervous system • Regulation of metabolic rate • Hyperthyroidism: person is nervous, high energy, higher resting body temperature, often tends to lose weight. May have emotional instability. • Hypothyroidism: person lacks energy, has difficulty focusing, often gains weight

19. Regulation of Thyroid Hormone Secretion Hypothalamus Thyrotropic Releasing Hormone (TRH) is carried to the anterior pituitary by the portal capillaries T3 and T4 also provide negative feedback to the hypothalamus and inhibit TRH secretion TRH Anterior Pituitary Thyroid Stimulating Hormone (TSH) is carried to the Thyroid gland by the general circulation TSH Thyroid Gland The Thyroid Gland releases T3 andT4 into the general circulation. T3 and T4 increase metabolic rate, increase body temperature and effect nervous tissue T3 and T4

20. Cycles of Releasing Hormones, Tropic Hormones and Direct Acting Hormones HormoneLevel TRH TSH T3 & T4 Time

22. The Adrenal Gland

23. Adrenal Medulla • Secretes Epinephrine and Norepinephrine directly into the blood stream during times of immediate threat (stress). • Regulated directly by the nervous system. When the sympathetic nervous system is activated, sympathetic nerves stimulate the adrenal medulla.

24. Adrenal Cortex • Produces a wide variety of steroid hormones that regulate sodium levels in the blood (Aldosterone), sex hormones (low levels), and glucocorticoids (cortisol) which plays an important role in managing long-term stress. • Effects of Cortisol - increases blood glucose levels, increases blood lipids, increases blood pressure, suppresses the immune response.

25. Regulation of Cortisol Secretion Hypothalamus Corticotropic Releasing Hormone (CRH) is carried to the anterior pituitary by the portal capillaries Cortisol also provides negative feedback to the hypothalamus and pituitary CRH Anterior Pituitary Adrenocorticotropic Hormone (ACTH) is carried to the Adrenal gland by the general circulation ACTH Adrenal Cortex The Adrenal Cortex releases cortisol into the general circulation. Increased blood glucose, increased blood fatty acids,increased blood pressure,suppression of immune system Cortisol