1. Allied Health Sciences I Unit P
The Endocrine System
Allied Health Sciences I
Unit P

2. Functions of the Endocrine System
Secrete hormones
Hormones are chemical messengers that coordinate and direct target cells and organs.
Hormone control
Negative feedback = drop in hormone level triggers a chain reaction
Blood level of hormone falls
Brain gets message and sends out hormone to stimulate gland
Gland secretes more hormone
When blood level of hormone increases, brain hormones stop

3. Functions of Endocrine System
Nervous control
In some cases, sympathetic nervous system causes direct release of hormone from gland (for example, when stress causes the adrenal medulla to secrete adrenalin)

4. Two types of glands Endocrine Exocrine
Secrete hormones directly into the bloodstream
ductless
Exocrine
Secrete substance through a duct
Sweat, salivary, lacrimal and pancreas

5. Structures of the Endocrine System
Anterior Pituitary Gland
Posterior Pituitary Gland
Thyroid Gland
Parathyroid glands
Thymus Gland
Adrenal Glands
Ovaries
Testes
Pancreas
Pineal Gland

6. The Anterior Pituitary Gland
The entire pituitary gland is the size of a grape.
It is located on the underside of the brain in the sella turcica.
The anterior lobe secretes 7 hormones:
Growth hormone or GH or somatotrophin-responsible for growth and development.
Prolactin hormone or PRL: responsible for stimulating milk production after childbirth
Thryroid-stimulating hormone or TSH: stimulates growth and secretion of the thyroid gland

7. The Anterior Pituitary Gland
Hormones cont.:
Adrenocorticotropic hormone or ACTH: stimulates growth and secretion of the adrenal cortex
Follicle-stimulating hormone or FSH: stimulates the growth of the graafian follicle and production of estrogen in the female and production of sperm in the male
Luteinizing hormone or LH: stimulates ovulation and formation of the corpus luteum which produces progesterone in the female
Interstitial-cell stimulating hormone or ICSH: needed for the production of testosterone in the male

8. The Posterior Pituitary Gland
The posterior pituitary gland produces two hormones:
Vasopressin: this converts to ADH in the bloodstream. ADH helps with water balance.
Oxytocin: causes contractions of the uterus during childbirth and during breastfeeding

9. The Thyroid Gland
It is located behind the cricoid cartilage in the neck and is about 2 inches long.
It produces three hormones:
Thyroxine (T4) and triiodothyronine (T3): controls the rate of metabolism, protein synthesis and the breakdown of liver glycogen.
Calcitonin: controls the calcium level in the bloodstream when it gets too high

10. The Parathyroid Glands
There are four of these and are the size of a grain of rice. They are attached to the posterior side of the thyroid gland.
It secretes one hormone:
Parathormone: also controls the calcium level when it gets too low

11. The Thymus Gland
The thymus gland is located beneath the sternum and decreases in size after puberty.
It secretes several hormones but the most important is:
Thymosin: stimulates lymphoid cells to produce T cells which help with immunity

12. The Adrenal Glands
There are two adrenal glands located on the top of each kidney.
There are two parts: the cortex and the medulla.
The cortex secretes three corticoids (which act as antiinflammatory agents):
Mineralocorticoids: mainly aldosterone which speeds sodium and water reabsorption in the kidneys
Glucocorticoids: mainly cortisone and cortisol, increases the amount of glucose in the blood
Androgens: male sex hormones that produce male sexual characteristics

13. The Adrenal Glands (cont.)
The medulla of the adrenal gland produces one hormone:
Epinephrine: increases heart rate, blood pressure and flow of blood; decreases intestinal activities

14. The Ovaries They are located in the female pelvis.
They produce two hormones:
Estrogen: promotes growth of primary and secondary sexual characteristics
Progesterone- develops excretory portion of mammary glands, aids in maintaining pregnancy

15. The Testes They are located in the male scrotum.
They produce one hormone:
Testosterone: develops primary and secondary sexual characteristics; stimulates maturation of sperm

16. The Pancreas The pancreas is located behind the stomach.
It produces two hormones:
Insulin: essential to the metabolism of carbohydrates, reduces blood sugar level
Glucagon: stimulates the liver to release glycogen and converts it to glucose to increase blood sugar levels

17. The Pineal Gland The pineal gland is located at the base of the brain.
It produces one hormone:
Melatonin: relates to the sleep cycle

18. Prostaglandins
Hormones called prostaglandins are secreted in various tissues. What the prostaglandins do depend on which tissue is secreting them. Some may cause constriction while others cause dilation. Prostaglandins can be used to induce labor and cause severe muscular contractions of the uterus.

19. Acromegaly
This occurs when hypersecretion of the growth hormone occurs.
Overdevelopment of the bones of the face, hands and feet occur.
Patients may have lethargy and headaches.
Tx. is drug therapy and radiation therapy.

20. Gigantism
This is an overgrowth of the long bones leading to excessive tallness.
This is due to hyperfunctioning of the pituitary gland during preadolescence.
Tx. is drug therapy and radiation therapy

21. Dwarfism
Hypofunctioning of the pituitary gland during childhood leads to dwarfism.
The body of a dwarf is normally proportioned and intelligence is normal.
Tx. Is early diagnosis and injections of the human growth hormone.

22. Hyperthyroidism
Hyperthroidism is an overactivity of the thyroid gland.
The gland becomes enlarged.
Patients may feel hot, have fast growing, rough fingernails, increased blood pressure and heart beat.
Patients may exhibit goiter and exopthalmos.
Tx. is partial or total removal of the thyroid, drugs to reduce thyroxine, radiation

23. Hypothyroidism The thyroid gland does not secrete enough thyroxine.
Iodine deficiency may cause adult hypothyroidism.
Myxedema causes the face to swell, weight gain and memory failure. Tx. is the thyroid hormone.
Occuring in infancy and early childhood, cretinism causes mental retardation and lack of physical growth. Tx. Is the thyroid hormone; however complete recovery is not possible.

24. Cushing’s Disease
This results from hypersecretion of the glucocorticoid hormones from the adrenal cortex. It may be caused by a tumor or prolonged use of prednisone.
The most common characteristics are a “moon” face and a “buffalo” hump.
Tx. Is removal of the tumor or gradual decrease of use of the prednisone.

25. Addison’s Disease
It is caused by decreased functioning of the adrenal cortex.
It is characterized by a “bronzing” of the skin.
Tx. is replacement of the deficient hormones.

26. Tetany
Caused by hypoparathyroidism, decreased calcium levels affect functions of nerves
Symptoms = convulsive twitching develops, person dies of spasms in the respiratory muscles
Rx = vitamin D, calcium and parathormone

27. Diabetes Mellitus
This is caused by decreased secretion of insulin in the islets of Langerhans.
There are two types: Type I- children and young adults and Type II- adults.
Type I requires insulin to control the glucose levels.
Type II may be controlled through diet and oral meds or may require injections.
Polyuria, polydypsia and polyphagia are typical symptoms.

28. Diabetes Insipidus
This is caused by a drop in the ADH (antidiuretic hormone) secondary to dysfunction of the posterior lobe of the pituitary gland. The person has excessive thirst.