The Endocrine System

1. The Endocrine System • Controls many body functions • exerts control by releasing special chemical substances into the blood called hormones • Hormones affect other endocrine glands or body systems • Derives its name from the fact that various glands release hormones directly into the blood, which in turn transports the hormones to target tissues via ducts.

2. The Endocrine System • Exocrine glands - transport their hormones to target tissues via ducts. • Endocrine Emergencies: • from common: • Diabetes • to the unusual: • Thyrotoxicosis

3. The Endocrine System • Consists of several glands located in various parts of the body. • Pituitary gland: a small gland located on a stalk hanging from the base of the brain - AKA • “The Master Gland” • Primary function is to control other glands. • Produces many hormones. • Secretion is controlled by the hypothalamus in the base of the brain.

4. The Endocrine System • The Pituitary Gland is divided into 2 areas, which differ • structurally and functionally • each area has separate types of hormone production. • The two segments are: • Posterior Pituitary: • produces oxytocin and antidiuretic hormone (ADH) • Anterior Pituitary: • produces thyroid-stimulating hormone (TSH) • growth hormone (GH) • adrenocorticotropin (ACTH) • follicle-stimulating hormone (FSH)

5. The Endocrine System • And even more… • luteinizing hormone (LH) • prolactin • Let’s go over these one at a time... • Posterior Pituitary • Oxytocin (the natural form of pitocin) • stimulates gravid uterus • causes “let down” of milk from the breast. • ADH (vasopressin) causes the kidney to retain water.

6. The Endocrine System • Anterior Pituitary • Primarily regulates other endocrine glands • rarely a factor in endocrinological emergencies • TSH stimulates the thyroid gland to release its hormones, thus  metabolic rate • Anterior Pituitary… • Growth hormone (GH) •  glucose usage •  consumption of fats as an energy source • ACTH stimulates the adrenal cortex to release its hormones • FSH & LH stimulates maturation & release of eggs from ovary.

7. The Endocrine System • The Thyroid Gland • lies in the anterior neck just below the larynyx. • Two lobes, located on either side of the trachea, connected by a narrow band of tissue called the isthmus. • Sacs inside the gland contain colloid • Within the colloid are the thyroid hormones: • thyroxine (T4) • triiodothyronine (T3) • When stimulated (by TSH or by cold), these are released into the circulatory system and  the metabolic rate. • “C” cells within the thyroid produce the hormone calcitonin.

8. The Endocrine System • Calcitonin, when released, lowers the amount of calcium in the blood. • Inadequate levels of thyroid hormones = hypothyroidism, or Myxedema. • Myxedema symptoms: • Facial bloating • weakness • cold intolerance • lethargy • altered mental status • oily skin and hair • TX: replacement of thyroid hormone.

9. The Endocrine System • Increased thyroid hormone release causes hyperthyroidism, commonly called Graves’ disease. • Signs and symptoms: • insomnia, fatigue • tachycardia • hypertension • heat intolerance • weight loss • Long term hyperthyroidism: • Exopthalmos • bulging of the eyeballs (picture Barbara Bush) • In severe cases - a medical emergency called thyrotoxicosis can result.

10. The Endocrine System • Parathyroid Glands • small, pea-shaped glands, located in the neck near the thyroid • usually 4 - number can vary • regulate the level of calcium in the body • produce parathyroid hormone -  level of calcium in blood • Hypocalcemia can result if parathyroids are removed or destroyed.

11. The Endocrine System • Pancreas • a key gland located in the folds of the duodenum • has both endocrine and exocrine functions • secretes several key digestive enzymes • Islets of Langerhans • specialized tissues in which the endocrine functions of the pancreas occurs • include 3 types of cells: • alpha ( ) • beta () • delta () • each secretes an important hormone.

12. The Endocrine System • Alpha () cells release glucagon, essential for controlling blood glucose levels. • When blood glucose levels fall,  cells  the amount of glucagon in the blood . • The surge of glucagon stimulates the liver to release glucose stores (from glycogen and additional storage sites). • Also, glucagon stimulates the liver to manufacture glucose - • gluconeogenesis.

13. The Endocrine System • Beta Cells () release insulin (antagonistic to glucagon). • Insulin  the rate at which various body cells take up glucose. Thus, insulin lowers the blood glucose level. • Insulin is rapidly broken down by the liver and must be secreted constantly. • Delta Cells () produce somatostatin, which inhibits both glucagon and insulin.

14. The Endocrine System • Adrenal Glands • 2 small glands that sit atop both kidneys. • Each has 2 divisions, each with different functions. • the Adrenal Medulla secretes the catecholamine hormones norepinephrine and epinephrine (closely related to the sympathetic component of the autonomic nervous system).

15. The Endocrine System • The Adrenal Cortex secretes 3 classes of hormones, all steroid hormones: • gluticocorticoids mineralocorticoids • androgenic hormones • One at a time… • gluticocorticoids: • accounts for 95% of adrenal cortex hormone production •  the level of glucose in the blood • Released in response to stress, injury, or serious infection - like the hormones from the adrenal medulla.

16. The Endocrine System • Mineralocorticoids: • work to regulate the concentration of potassium and sodium in the body. • Prolonged  in adrenal cortex hormone results in Cushing’s Disease. • Signs & Symptoms of Cushing’s Disease: •  in blood sugar levels • unusual body fat distribution • rapid mood swings

17. The Endocrine System • And - if there is an  in mineralocorticoids as well • A serious electolyte imbalance will occur due to the  potassium excretion by the kidney, which results in hypokalemia. • Sodium can also be retained by the kidney, resulting in hyponatremia. • Causes: • dysrhythmias • coma • death • usually results from a tumor - TX? Removal of tumor.

18. The Endocrine System • Gonads and Ovaries: • the endocrine glands associated with human reproduction. • Female ovaries produce eggs • Male gonads produce sperm • both have endocrine functions. • Ovaries: • located in the abdominal cavity adjacent to the uterus. • Under the control of LH and FSH from the anterior pituitary they manufacture • estrogen • protesterone

19. The Endocrine System • Estrogen and Progesterone have several functions, including sexual development and preparation of the uterus for implantation of the egg. • Testes: • located in the scrotum • produce sperm for reproduction • manufacture testosterone - • promotes male growth and masculinization • Controlled by anterior pituitary hormones FSH and LH.

20. The Endocrine System • Endocrine Emergencies: • Diabetes Mellitus • one of the most common diseases in North America. •  insulin secretion by the Beta () cells of the islets of Langerhans in the pancreas. • Complications of Diabetes: • contributes to heart disease • stroke • kidney disease • blindness

21. The Endocrine System • Pathophysiology of Diabetes: • Glucose Metabolism • Glucose (dextrose) is a simple sugar required by the body to produce energy. • Sugars, or carbohydrates, are 1 of 3 major food sources used by the body. • The other 2 major food sources are • proteins • fats • Most sugars in the human diet are complex and must be broken down into simple sugars: glucose, galactose and fructose - before use.

22. The Endocrine System • Breakdown of sugars is carried out by enzymes in the gastro intestinal system. • As simple sugars, these are absorbed from the GE system into the body. • More than 95% enter the body as glucose. • To be converted into energy, glucose must first be transmitted through the cell membrane. BUT - the glucose molecule is large and doesn’t readily diffuse through the cell membrane.

23. The Endocrine System • Glucose must pass into the cell by binding to a special carrier protein on the cell’s surface. • Facilitated diffusion - doesn’t use energy. The carrier protein binds with the glucose and carries it into the cell. • The rate at which glucose can enter the cell is dependent upon insulin levels. • Insulin serves as the messenger - travels via blood to target tissues. • Combines with specific insulin receptors on the surface of the cell membrane.