Chapter 7The endocrine system

The endocrine system, along with the nervous system, allows for communication between

distant sites in the body .the endocrine system has three components :

1-endocrine glands that secrete chemical messengers into the bloodstream ;

2-the chemical messengers themselves, called hormones ;

3-and the target cells or organs that respond to the hormones.

Conditions of Disease or InjuryHypothyroidismResult from malfunction of the thyroid gland, the pituitary,

or the hypothalamus .-If it results from thyroid gland malfunction, low TH (thyroxin

hormone) levels are accompanied by high TSH( thyroid stimulating hormone) and high TRH (thyroid releasing hormone) because of the lack of negative feedback on the pituitary and hypothalamus by TH.

-If hypothyroidism results from pituitary malfunction, low levels of TH are caused by low TSH. TRH from the hypothalamus is high because there is no negative

feedback on its release by TSH or TH .-

- Hypothyroidism caused by hypothalamic malfunction results in low TH, low TSH, and low TRH.

Causes of Hypothyroidism• - Hashimoto's disease, also called autoimmune

thyroiditis, results from autoantibody destruction of thyroid gland tissue.

• - Endemic goiter is hypothyroidism caused by a dietary deficiency of iodide. A goiter is an enlargement of the thyroid gland.

• - Thyroid carcinoma may cause hypothyroidism or hyperthyroidism.

Clinical Manifestations• - Sluggishness and slow thinking, and slow

movements.• - Decreased heart rate.• - Edema of the skin, especially under the eyes and in

the ankles(myxedema)• - Intolerance to cold temperatures.• - Decreased metabolic rate, decreased caloric

requirements, decreased appetite and nutrient absorption across the gut.

• - ConstipationDiagnostic ToolsMeasuring levels of TH (both T3 and T4), TSH, and TRH

will allow diagnosis of the condition and localization of the problem .

Hyperthyroidism Hyperthyroidism is excessive levels of circulating TH.

-Increased TH caused by malfunction of the thyroid gland is accompanied by decreased TSH and TRF, as a result of the negative feedback on their release by TH.

-Hyperthyroidism caused by malfunction of the pituitary results in high TH and high TSH. TRF is low because of negative feedback from TH and TSH.

-Hyperthyroidism caused by malfunction of the hypothalamus shows high TH accompanied by excess TSH and TRH.

Clinical Manifestations• - Increased heart rate.• - Increased muscle tone, tremors, irritability• - Increased basal metabolic rate and heat production,

intolerance to heat, excess sweating.• - Weight loss, increased hunger.• - Exophthalmos (bulging of the eyes) may develop.• - Increased number of bowel movements.• - Goiter (usually), which is an increase in the size of the

thyroid gland. Diagnostic tools - Measuring levels of TH (both T3 and T4), TSH, and TRH will

allow diagnosis of the condition and localization of the problem.

Adrenal Insufficiency

Adrenal insufficiency is a decrease in the circulating level of the glucocorticoids. The mineralocorticoid aldosterone may also be reduced.

Adrenal insufficiency may be caused by dysfunction of the adrenal gland, called primary adrenal insufficiency, or by dysfunction of the pituitary or hypothalamus. Both of these latter conditions cause secondary adrenal insufficiency.

•Primary adrenal insufficiency is characterized by low levels of glucocorticoids, especially cortisol, accompanied by high ACTH( adreno corticotropic hormone) and high CRH( cortzone releasing hormone) because there is no negative feedback on their release.

•If the cause of adrenal insufficiency is secondary to a pituitary dysfunction, low glucocorticoids will be accompanied by low ACTH and high CRH. In this case, adrenal androgens will also be low.

•If there is zero ACTH, aldosterone levels will be reduced. If adrenal insufficiency is caused by a hypothalamus malfunction, the glucocorticoids, ACTH, and CRH will be low.

Diseases of Adrenal Insufficiency• Primary adrenal insufficiency, called Addison's disease,

occurs from destruction of the adrenal cortex. The disease is usually autoimmune, and may results from infections such as TB or tumors.

Addison's disease is characterized by low glucocorticoid levels accompanied by high ACTH and high CRH. Total loss of the adrenal gland results in the loss of adrenal androgens and aldosterone as well. Aldosterone deficiency leads to increased loss of sodium in the urine, resulting in hyponatremia (decreased sodium in the blood), dehydration, and hypotension (because water loss in the urine frequently accompanies the loss of sodium). Decreased potassium excretion in the urine will lead to hyperkalemia (increased potassium concentration in the blood).

Clinical Manifestations• - Depression, because cortisol levels influence mood

and emotions.• - Fatigue, related to hypoglycemia, and decreased

gluconeogenesis.• - Anorexia, vomiting, diarrhea, and nausea.• - Hyperpigmentation of the skin if ACTH levels are high

(primary adrenal insufficiency) as a result of ACTH having melanin-stimulating hormone like effects on the skin.

• - Sparse body hair in women, if the adrenal cells producing androgens are destroyed .

• - Inability to respond to stressful situations, perhaps leading to severe hypotension.

Glucocorticoid Excess Glucocorticoid excess refers to any condition in

which there are very high levels of circulating glucocorticoids. The cause of glucocorticoid excess may reside at the level of the adrenal gland or at the pituitary/hypothalamic level. If the cause of glucocorticoid excess is primary adrenal gland hypersecretion, there is usually an adrenal tumor present. In this situation, low ACTH and low CRH levels will be present as a result of negative feedback from high glucocorticoids. Adrenal androgen levels will be low because ACTH is low. Bronzing of the skin will not occur.

Diseases of Excess Glucocorticoids• - Cushing's syndrome refers to any condition of

high glucocorticoids and includes glucocorticoid excess caused by therapeutic administration of corticosteroids.

• - Cushing's disease refers to high glucocorticoids caused specifically by malfunction of the anterior pituitary resulting in excess ACTH.

Clinical Manifestations• - Altered fat metabolism leading to fat pads on the

back (buffalo hump), moon face, protruding abdomen with thin extremities, and stretch marks on breasts, thighs, and abdominal surface.

• - Muscle weakness from protein breakdown.• - Hypertension as a result of increased

catecholamine responsiveness.• - Weight gain resulting from strong appetite

stimulation.• - Inhibition of immune and inflammatory reactions,

leading to poor wound healing.• - Masculinization of women and children as a result

of adrenal androgen stimulation if ACTH levels are high.

• - Bronzing of the skin if ACTH levels are high.

Growth Hormone Deficiency(Dwarfism)• Growth hormone deficiency is a decrease in circulating

levels of GH. Most cells of the body will be affected. GH deficiency is usually clinically recognized only in children. Usually is caused by a pituitary adenoma .

• Clinical Manifestations• - proportional short stature .• - Delayed onset of pubertyGrowth Hormone Excess• Growth hormone excess is the increase in circulating

levels of GH usually caused by a GH-secreting tumor of the anterior pituitary.

Diseases of GH Excess• - Gigantism, a disease of excess longitudinal growth of

the bones of the skeleton, is seen as a result of GH excess before puberty.

• - Acromegaly, a disease of connective tissue proliferation, is seen in adults with GH excess. Because long bone growth has stopped in adults, GH excess cannot cause growth of the skeleton. It is associated with growth of the cartilage of the hands, feet, nose, jaw, chin, and facial bones.

Clinical Manifestations• - Tall stature with gigantism.• - Thickening of the fingers, jaw, forehead, hands, and

feet with acromegaly.

Gonadotropin Deficiency Gonadotropin deficiency is a decrease in circulating

levels of FSH and LH. Clinical Manifestations• - Amenorrhea (lack of menstrual periods), vaginal,

uterine, and breast atrophy in women.• - Testicular atrophy and reduction in beard growth

in men.

Syndrome of Inappropriate Antidiuretic Hormone (ADH)

(SIADH) is characterized by increased release of ADH from the posterior pituitary

Clinical Manifestations• - Water retention and weight gain.• - Decreased urinary output.• - Nausea and vomiting worsening with the degree of

water intoxication. Diagnostic Tools Blood tests measuring increased levels of ADH with low

plasma sodium concentration ( hyponatremia) .

Diabetes Insipidus Diabetes insipidus is a disease of decreased ADH

production. Clinical Manifestations - Large volumes of dilute urine. - Polydipsia (excessive thirst). Diagnostic Tools Blood tests measuring decreased levels of ADH with

hypernatremia will allow diagnosis of the condition. Complications Severe dehydration may occur if large volumes of

drinking water are unavailable.

Chapter 8The Musculoskeletal System

Muscular Dystrophy It refers to a variety of diseases characterized by

wasting of the muscles. Muscle cells die and are phagocytized by cells of the inflammatory system, leading to scaring and loss of muscle function.

The most common form of muscular dystrophy is Duchenne's muscular dystrophy, a sex-linked disorder passed on the X chromosome and seen almost exclusively in males. In approximately 50% of cases, the disease shows a clear family history and is passed from mother to son.

Clinical Manifestations of Duchenne's Muscular

Dystrophy - Waddling gait, and frequent falls in toddlers. - Walking on toes because of anterior tibial

weakness. - Decreased deep tendon reflexes. - Pseudohypertrophy of the calf muscles. - Gowers' maneuver, whereby the child uses his

arms to push up onto his legs when standing up from the floor, is seen during the toddler years.

- Immobility and confinement to a wheelchair by the early teens.- Curvature of the spine (kyphoscoliosis) caused by weakness of the postural muscles.- Frequent respiratory infections from failure to fully expand the lungs.

Diagnostic Tools- Serum levels of the muscle enzyme creatinine phosphokinase (CPK) are elevated.- Muscle biopsy will demonstrate cell death, scar tissue, and fatty infiltration.- Electromyography recordings (measurements of electrical signals in a muscle) will be reduced.

Acute Osteomyelitis Osteomyelitis is an acute infection of

the bone that may occur in two froms: 1-Hematogenous osteomyelitis :blood-

borne infection 2-Exogenous osteomyelitis after

contamination of an open fracture or surgical reduction.

Clinical Manifestations-In children may include fever, chills, and a reluctance to move a particular limb. -In adults, symptoms may be vague and include fever, fatigue, and malaise. -A urinary, respiratory tract, ear, or skin infection frequently precedes hematogenous osteomyelitis.-Exogenous osteomyelitis typically presents with evidence of injury and inflammation at the site of pain. Fever and regional lymph node enlargement occur.

Osteoporosis Is a metabolic bone disease characterized by a

severe reduction in bone density, leading to easy bone fracture. Osteoporosis occurs when the rate of bone resorption greatly exceeds the rate of bone formation.

Causes of Osteoporosis The rate of bone formation decreases progressively

with age, beginning at approximately age 30 or 40. The denser the bones are before that time, the less likely osteoporosis will occur. As people age into their 70s and 80s, osteoporosis becomes a common disease.

Osteomalacia and Rickets Osteomalacia is a metabolic bone disease

seen in adults. It is caused by decreased mineralization of the osteoid as a result of a deficiency of calcium, phosphate, or from a vitamin D deficiency or from renal disease.

Rickets is a bone disease in children caused by vitamin D deficiency.

Clinical Manifestations - Osteomalacia may be symptomless until a fracture occurs. Vertebral collapse is common, with associated changes in posture and height. - Rickets is characterized by permanent skeletal deformity, including bowed legs, lumbar lordosis, and rib and skull deformity. Inability to to walk without support and may also show poor dentition.Diagnostic Tools - Radiograph evaluation can demonstrate reduced bone ossification. - Measurements of serum calcium and phosphate will be low in severe cases.

Osteoarthritis Is a degenerative bone disease characterized by loss of

articular (joint) cartilage. Without cartilage buffering, the underlying bone is irritated, leading to degeneration of the joint.

CLinical Manifestations - Pain and stiffness in one or more of the joints,

commonly the hands, wrists, feet, knees, upper and lower spine, hips, and shoulders. Pain may be associated with tingling or numbness, especially at night.

- Swelling of the affected joints, with a decreased range of motion. Joints may appear deformed.

Rheumatoid Arthritis (RA) is a chronic, inflammatory disease that causes

degeneration of connective tissue ,first is the synovial membrane and spreads to the surrounding structures of the joint, including the articular cartilage and the fibrous joint capsule. Eventually, the ligaments and tendons become inflamed.

Clinical Manifestations - Onset of RA is characterized by general symptoms of

inflammation, including fever, fatigue, body aches, and joint swelling. Joint tenderness and stiffness develop.

- Decreased range of motion, joint deformity and muscular contractions.

Talipes Equinovarus Talipes equinovarus, also called

clubfoot, is a congenital abnormality characterized by deformity of the bones and soft tissue of the foot. The front portion of the foot is turned in whereas the rear of the foot is inverted.