Unit 4.03 & 4.04 Endocrine System Lecture
A. Introduction
1. Composed of a group of ductless (without tubes) glands
2. Secrete substances called hormones directly into the bloodstream
3. Includes the pituitary; thyroid, parathyroid, adrenals, pancreas, ovaries, testes, thymus, pineal body, and
placenta
B. Hormones
1. Substances produced and secreted by endocrine glands
2. Frequently called chemical messengers
3. Transported throughout the body by the bloodstream
4. Perform many functions
a. Stimulate exocrine glands (glands with ducts or tubes) to produce secretions
b. Stimulate other endocrine glands
c. Regulate growth and development
d. Regulate metabolism
e. Maintain fluid and chemical balance
f. Control various sex processes
C. Pituitary gland
1. Often called the master gland of the body
2. Located at the base of the brain in a small, bony depression of the sphenoid bone called the Sella Turcica
3. Divided into two sections or lobes: anterior and posterior
4. Produces many hormones that affect other glands
5. Diseases Affecting the Pituitary Gland
a . Acromegaly
(1) Over-secretion of somatotropin or growth hormone in an adult
(2) Usually caused by a tumor of pituitary
(3) Symptoms
aa. Bones of the hands, feet, and face enlarge and create a grotesque appearance
bb. Skin and tongue thicken and slurred speech develops
(4) Treatment: surgical removal and/or radiation of the tumor
b. Giantism
(1) Over-secretion of somatotropin before puberty
(2) Symptoms
aa. Excessive growth of long bones and extreme tallness
bb. Decreased sexual development
cc. Retarded mental development at times
(3) Treatment if tumor involved- surgical removal or radiation
c. Diabetes Insipidus
(1) Condition caused by a decreased secretion of vasopressin or anti-diuretic hormone (ADH)
(2) Low level of ADH results in water not being reabsorbed in the kidneys
(3) Symptoms: polyuria, polydipsia, dehydration, weakness, constipation, and dry skin
(4) Treatment: ADH (replace missing hormone)
d. Dwarfism
(1) Under-secretion of somatotropin
(2) Causes: tumor, infection, genetic factors, or injury
(3) Symptoms
aa. Small body size and short extremities
bb. Lack of sexual development
cc. Mental development is normal
(4) If diagnosed early, it can be treated with injections of somatotropic hormone for 5 or more
years until long bone growth is complete
D. Thyroid gland
1. Synthesizes hormones that regulate body’s metabolism and control the level of calcium in the blood
2. Located in front of the upper part of the trachea in the neck
3. Has two lobes
a. One on either side of the larynx or voice box
b. Lobes connected by a small piece of tissue called the isthmus
4. Requires iodine obtained from certain food and iodized salt to produce its hormone
5. Diseases affecting the thyroid gland
a. Goiter
(1) Enlargement of the thyroid gland
(2) Causes: hyperactive thyroid, iodine deficiency, over-secretion of thyroid
stimulating hormone by the pituitary gland, or a tumor
(3) Symptoms
aa. Enlargement of the thyroid
bb. Dysphagia, or difficult swallowing
cc. Cough and a choking sensation
(4) Treatment is directed toward eliminating cause
aa. Iodine is given if a deficiency exists
bb. Surgery to remove very large goiters
b. Hyperthyroidism
(1) Over-activity of the thyroid gland
aa. Causes an increased production of thyroid hormones
bb. Increase in the basal metabolic rate (BMR)
(2) Symptoms
aa. Extreme nervousness tremors irritability
bb. Rapid pulse and hypertension
cc.Weight loss caused by increased BMR
dd. Goiter formation
(3) Treatment
aa. Radiation to destroy part of the thyroid
bb. Thyroidectomy or surgical removal of thyroid
c. Graves’ disease
(1) Severe form of hyperthyroidism
(2) More common in women than men
(3) Symptoms
aa. Strained and tense facial expression
bb. Exophthalmia or protruding eye bails
cc Goiter
dd. Nervous irritability and emotional instability
ee. Tachycardia
ff.Tremendous appetite with weight loss and diarrhea
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(4) Treatment
aa. Medication to inhibit synthesis ofthyroxine
bb. Radioactive iodine to destroy thyroid tissue
cc. Thyroidectomy
d. Hypothyroidism
(1) Under-activity of thyroid gland and a deficiency of thyroid hormones
(2) Woman forms exist cretinism and myxedema
(3) Cretinism
aa. Develops in infancy or early childhood
bb Results m a lack of mental and physical growth leading to mental retardation and an
abnormal dwarfed stature
cc. If diagnosed early, oral thyroid hormone can be given to minimize mental and
physical damage
(4) Myxedema
aa. Occurs m later childhood or adulthood
bb. Symptoms: coarse dry skin, slow mental function fatigue weakness, an intolerance
for cold, weight gain, edema, puffy eyes, and a slow pulse
cc Treatment: oral thyroid hormone to restore normal metabolism
E. Parathyroid glands
1. Four small glands
2. Located behind and attached to the thyroid gland
3. Hormone regulates the amount of calcium in the blood
a. Stimulates bone cells to break down bone tissue, and release calcium and phosphates into the blood
b. Causes the kidneys to conserve and reabsorb calcium
c. Activates intestinal cells to absorb calcium from digested foods
d. Most of the body’s calcium is in bone
e. Calcium circulating in the blood is very important for blood clotting, the tone ofheart muscle, and
muscle contraction
f .Constant exchange of calcium and phosphate between bone and blood
g. Parathyroid hormone plays an important function in maintaining proper level of circulating calcium
4. Disorders of the Parathyroid Glands
a. Hyperparathyroidism
(1) Over-activity of the parathyroid gland resulting in an overproduction of parathormone
(2) Results in hypercalcemia, which leads to formation of renal calculi, lethargy; gastrointestinal
disturbances, and calcium deposits on walls of blood vessels and organs
(3) Because calcium is drawn from bones, bones become weak, deformed, and likely to fracture.
(4) Often caused by an adenoma (glandular tumor)
(5) Removal of the tumor usually results in normal parathyroid function
b. Hypoparathyroidism
(1) Under activity of the parathyroid gland
(2) Causes a low level of calcium in the blood
(3) Symptoms
aa .Tetany: a sustained muscular contraction
bb. Hyperirritability of the nervous system
cc. Convulsive twitching
dd. Death if larynx and respiratory muscles involved
(4) Treatment: calcium; vitamin D, which increases the absorption of calcium and parathormone
F. Adrenal glands
1. Frequently called the suprarenal glands
2. One is located above each kidney
3. Each gland has two parts
a. Cortex or outer portion
(1) Secretes many steroid hormones
(2) Classified in three groups: mineralocorticoids, glucocorticoids, and gonadocorticoids
b. Medulla or inner portion
(1) Secretes two main hormones: epinephrine and norepinephrine
(2) mimic sympathetic nervous system and cause the fight or flight response
4. Diseases Affecting the Adrenal Gland
a. Addison’s disease
(1) Decreased secretion of aldosterone from the adrenal cortex
aa. Interferes with reabsorption of sodium and water
bb. Causes an increased level of potassium in blood
(2) Symptoms: dehydration, hypotension, mental lethargy weight loss, muscle weakness,
excessive pigmentation leading to a “bronzing” or yellow-brown color of the skin, hypoglycemia, and
edema
(3) Treatment
aa. Administration of steroid hormones
bb. Controlled intake of sodium
cc. Fluid regulation to combat dehydration
b. Cushing’s syndrome
(1) Oversecretion of glucocorticoids from adrenal cortex
(2) Causes: tumor of the adrenal cortex, excess production of ACTH by pituitary gland
(3) Symptoms: hyperglycemia, hypertension, muscle weakness, poor healing of wounds, a
tendency to bruise easily, a “moon” face, and obesity
(4) Treatment
aa. If tumor is cause, removal of the tumor
bb. Hormonal therapy to replace missing hormones
G. Pancreas
1. Fish-shaped organ located behind the stomach
2. Both an exocrine and endocrine gland
3. As an exocrine gland, it secretes pancreatic juices that are
a. Carried to the small intestine by the pancreatic duct
b. Aid in the digestion of food
4. Islets of Langerhans
a. Patches of tissue
(1) Located throughout the pancreas
(2) Contain special B or beta cells
b. Produce the hormone insulin, which is needed for the cells to take up sugar from the blood
5. Alpha or A cells produce the hormone glucagon that increases the blood level of
glucose
6. Diabetes Mellitus
a. Chronic disease caused by a decreased secretion of insulin
b. Metabolism of carbohydrates, proteins, and fats is affected
c. TWO main types of diabetes mellitus
(1) Named according to the age of onset and need for insulin
(2) Insulin-dependent diabetes mellitus (IDDM)orType 1
aa. Usually occurs early in life and more severe
bb. Requires insulin for treatment
(3) Noninsulin-dependent diabetes mellitus (NIDDM) or Type 2
aa. Mature onset form of diabetes
bb. Frequently occurs in obese adults
cc. Controlled with diet and/or oral hypoglycemic medications
d. Symptoms
(I) Hyperglycemia: high blood sugar
(2) Polyuria: excessive urination
(3) Polydipsia: excessive thirst
(4)polyphagia excessive hunger with weight loss
(5) Glycosuria: sugar in the urine
(6) Fatigue
(7) Slow healing of skin infections
(8) Vision changes
(9) If not treated, diabetic coma and death may occur
e. Treatment
(1) Carefully regulated diet to control blood sugar
(2) Regulated exercise
(3) Oral hypoglycemic drugs or insulin injections
H. Ovaries
1, Sex glands or gonads of the female
2. Located in the pelvic cavity
3. One on each side of the uterus
4. Secrete hormones that regulate the menstruation and secondary sexual characteristics
I. Testes
1. Sex glands or gonads of the male
2. Located in the scrotal sac and suspended outside the body
3 Produce hormones that regulate sexual characteristics of the male
J. Thymus
Mass of tissue in the upper part of the chest under the sternum
2. Also contains lymphoid tissue
3 Active in early life in activating cells in the immune system
4. Atrophies or wastes away during puberty and becomes a small mass of connective tissue and fat
K. Pineal body
1 Small structure located in the brain
2. Attached to the roof of the third ventricle
3. Knowledge regarding the physiology of this gland is limited
L. Placenta
1 Temporary endocrine gland produced during pregnancy
2. Functions
a. Acts as a link between the mother and infant
b. Provides nutrition for the developing infant
c. Promotes lactation or the production of milk in the breasts
3. Expelled as the afterbirth after the birth of the child