CHAPTER 7

The endocrine system

INTRODUCTION:There are three components to the endocrine system :

•endocrine glands;

•Hormones; and the

•target cells or organs that respond to the hormones.

CONDITIONS OF DISEASE OR INJURY

I.  Hypothyroidism

It may result from malfunction of:• the thyroid gland, low TH, high TSH, high TRH•the pituitary, or , low TH, low TSH, high TRH•the hypothalamus, low TH, low TSH, low TRH.

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

HYPOTHYROIDISM

Clinical Manifestations

Sluggishness and slow thinking, and slow movements.• Bradycardia, enlarged heart (myxedemic heart), and decreased

cardiac output.• Edema of the skin, especially under the eyes and in the

ankles(myxedema)• Cold intolerance.• Decreased metabolic rate, decreased caloric requirements, anorexia,

and nutrient absorption across the gut.• Constipation.

HYPOTHYROIDISMDiagnostic Tools

Blood tests measuring levels of TH (both T3 and T4), TSH, and TRH

will allow diagnosis of the condition and localization of the problem

II. Hyperthyroidism , is excessive levels of circulating TH

Causes: malfunction of the thyroid gland , low TSH and TRF

HYPOTHYROIDISMpituitary , high TH, high TSH, low TRF

hypothalamus, high TH, 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.• -A staring appearance.• -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.• -Blood tests measuring levels of TH (both T3 and T4), TSH, and TRH will

allow diagnosis of the condition and localization of the problem at the level of the CNS or the thyroid gland.

• -Decreased serum lipids may accompany hyperthyroidism.

A D R E N A L I N S U F F I C I E N C Y

A decrease in the circulating level of the glucocorticoids.

Aldosterone may also decreases .

Types of adrenal insufficiency:•Primary; dysfunction of the adrenal gland, (low glucocorticoids, high

ACTH and high CRH)•Secondary; dysfunction of the pituitary or Hypothalamus (low glucocorticoids ,low ACTH, and high CRH) •If there is zero ACTH, aldosterone levels will be reduced .

DISEASES OF ADRENAL INSUFFICIENCY

Primary adrenal insufficiency, called Addison's

disease, occurs from destruction of the adrenal cortex

(low glucocorticoid , high ACTH , high CRH)

usually autoimmune, and may results from

infections such as TB or tumors.

Total loss of the adrenal gland results in the loss of

androgens, and aldosterone, which results in

increased loss of sodium in the urine (hyponatremia,

dehydration, and hypotension (because water loss in

the urine frequently accompanies the loss of Na).

ADDISON'S DISEASEDecreased potassium excretion in the urine will lead to hyperkalemia (increased potassium concentration in the blood). Clinical Manifestation:

• - Depression; cortisol influence mood and emotions.• - Fatigue; hypoglycemia, and decreased

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

levels are high (primary adrenal insufficiency) ; 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:Any condition in which there are very high levels of circulating

glucocorticoids.

Cause:• Adrenal gland, primary , tumor (low ACTH and low CRH

levels) Adrenal androgen levels will be low because ACTH is low. Bronzing of the skin will not occur.• Pituitary/hypothalamic level.

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.

Growth Hormone Deficiency(Dwarfism) 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 ExcessGrowth 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, excess longitudinal growth of the bones of the skeleton, results from GH excess before puberty.- Acromegaly, a disease of connective tissue

proliferation, is seen in adults with GH excess.

- 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 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 pituitaryClinical Manifestations

-Water retention and weight gain. -Decreased urinary output.

- Nausea and vomiting ; water intoxication.Diagnostic Tools- Blood tests (ADH with decreased plasma osmolality and hyponatremia)

Diabetes Insipidus is a disease of decreased ADH

production, secretion, or function.Clinical Manifestations

-Large volumes of dilute urine. -Polydipsia (excessive thirst).

Diagnostic ToolsBlood tests (ADH with increased plasma osmolality and hypernatremia)ComplicationsSevere dehydration may occur if large volumes of drinking water are unavailable.