Endocrine system

The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In vertebrates, the hypothalamus is the neural control center for all endocrine systems.

1. Human growth hormone (hGH) It stimulates the growth of bones, muscles, cartilage and other tissues Stimulates protein metabolism, tissue repair and lipolysis in most of body tissues Thyroid-stimulating hormone ( TSH) Stimulates triiodothyronine (T3) and thyroxine (T4) synthesis and release from thyroid gland Stimulates iodine absorption by thyroid gland Adrenocorticotropic hormone (ACTH) Stimulates corticosteroids ( glucocorticoids and mineralocorticoids ) Synthesis of sex hormones (androgens) and release.

2. Melanocyte stimulating hormone(MSH) Increases the production of melanin in melanocytes in the skin Thus causing a deepening pigmentation or darkening of the skin Prolactin Stimulates milk production and secretion by the mammary glands Follicle-stimulating hormone (FSH ) In Females: Stimulates maturation of ovarian follicles in ovary In males: Stimulates maturation of sperms Stimulates spermatogenesis Luteinizing hormone (LH)   In female: Stimulates ovulation and stimulates formation of corpus luteum In males: Stimulates testosterone synthesis by testes

3. Posterior pituitary Hormones Functions Antidiuretic Hormone ADH Decreases urine volume Maintains the water balance by increasing water reabsorption in the tubules of the nephrons of kidneys, thereby increasing blood volume Oxytocin Stimulates contraction of smooth muscles of the pregnant uterus in the late stages of child birth. Stimulates release of milk during breastfeeding i.e. lactation.

4. Dwarfism

5. GIGANTISM

6. Thyroid Gland cells Thyroid gland hormones Functions   Follicular cells   Thyroid Hormones Triiodothyronine ( T3 ) and Thyroxine ( T4 ) Increasing basal metabolic rate (BMR) & heat production Regulating metabolism of carbohydrates, proteins and fats Normal growth and development of skeleton and nervous system Increasing the rate of protein synthesis Stimulate RNA polymerase I and ll , thereby promoting protein synthesis Stimulates body oxygen and energy consumption, thereby increasing the basal metabolic rate

7. Parafollicular cells Calcitonin Calcitonin hormone decreases the calcium and phosphate levels into the blood by increasing uptake of calcium and phosphate ions into the bones matrix. This hormone is important during childhood when bones undergo considerably changes in size and shapes.

8. Regulation of thyroid hormone

9.   Characteristic features Hypothyroidism during fetal life leads to Cretinism. This condition is prevalent in certain areas distant from the sea where soil and diet are deficient in iodine. Therefore there is insufficient iodine available for synthesis of T3 and T4 in such patients. Symptoms Retarded physical and mental growth Retarded sexual development Disproportionately short limbs Large protruding tongue Muscular weakness Dry skin  

10. Characteristic features Hypothyroidism during adult life leads to myxedema. Deficiency of T3 and T4 in adult life results in low basal metabolic rate. Myxedema is most common in females. Causes include ionizing radiations, anti-thyroid drug therapy etc. Symptoms Accumulation of fats on face i.e. puffy face Low body temperature Bulginess under the eye due to swelling Sleeping time up to 12-14 hours per day Decreased hair growth

11.   Characteristic features Extra enlargement of thyroid gland characterized by deficiency of T3 and T4 due to inadequate dietary iodine. The resultant low level of thyroid hormone in the blood stimulates secretion of TSH which causes thyroid gland enlargement.

12. Characteristic features Graves’ disease is an autoimmune disease characterized by enlargement of thyroid glands due to excessive secretion of T3 and T4 which is not regulated by normal negative feedback mechanism. Hypersecretion of thyroid hormones increases food intake, basal metabolic rate and heat production. Generally women are more affect than men mostly at 30-50 years of age. Symptoms Protrusion of the eyes due to deposition of excess fats behind eyeballs Difficulty during blinking of eyelids and sleep leads to incomplete closure of eyelids and drying of conjunctiva hence eye infection may occur Increased sweating Basal metabolic rate increased

13. PANCREATIC GLAND SECRETIONS FUNCTIONS Exocrine pancreas made up of pancreatic acini cells Pancreatic juice: Pancreatic Amylase, Pancreatic Lipase, Trypsinogen, Chymotrypsinogen ,   Chemical digestion of carbohydrates, proteins and lipids Endocrine pancreas made up of pancreatic islets of Langerhans Hormones: Alpha cells: Glucagon Beta cells: Insulin Delta cells: Somatostatin     Increases blood glucose level Reduces blood glucose level Maintains glucagon and insulin secretion

14. Insulin (Beta cells) Lowers blood glucose levels by several mechanisms On liver cells Increases glycogenesis (glycogen synthesis) Reduces gluconeogenesis (glucose synthesis) Increases lipogenesis (lipid synthesis) On skeletal muscles Increases glucose uptake in muscle cells Increases glycogenesis (glycogen synthesis) Increases Protein synthesis On fat tissue Increases lipogenesis (lipid synthesis)

15. ADRENAL GLAND

16. ADRENAL CORTEX

17. Outer zone Zona glomerulosa Mineralocorticoids Aldosterone Maintain water & electrolyte balance It stimulates reabsorption of Na + , Cl - , HCO3 - and water and excretion of k + from kidney tubules

18. Middle zone Zona fasciculata Glucocorticoids Cortisol, Corticosterone, Cortisone Gluconeogenesis (formation of glucose) hyperglycemia Lipolysis (breakdown of triglycerides into fatty and glycerol and energy production) Metabolism of protein Anti-inflammatory action Resistance to stress in exercise, fasting, extreme temperature, high altitude, surgery, trauma, infection etc. Depress the immune response

19. Inner zone Zona reticularis Androgens ( Sex hormones)   Puberty: development of secondary sexual characteristics at 10-14 years of age Growth of axillary and pubic hairs in boys and girls Contribute in sex drive and sex behavior

20. ADRENAL MEDULLA

21. HORMONES SRCRETED FROM ADRENAL MEDULLA EFECTS CATECHOLAMINES Adrenaline, Noradrenaline are neurotransmitters of sympathetic division of autonomic nervous system Prepare the body for ‘fight or flight’ response under stress Cardiac stimulant action Increasing heart rate Increasing blood pressure Increasing basal metabolic rate Constriction of blood vessels Increasing blood supply to the heart, brain, skeletal muscles, skin, blood, vessels etc.

22. Addison’s disease

23. Cushing‘s syndrome

24. Thanking You