Endocrine System

What is the role of the hypothalamus in regulating pituitary control of endocrine function?

The coordinating center of the brain for endocrine, behavioral, and autonomic nervous system functions. It regulates the pituitary gland by controlling the release of hormones that stimulate or inhibit hormone secretion. The pituitary then controls target endocrine glands

What is the major difference between positive and negative feedback control mechanisms?

Positive increases or amplifies original stimulus; negative decreases or inhibits original stimulus, helps maintain hormone levels within normal range

Describe the hypothalamic-pituitary-thyroid feedback system

1. hypothalamus stimulates the pituitary

2. anterior pituitary produces thyroid stimulating hormone (TSH)

3. TSH stimulates the thyroid gland

4. Thyroid produces T3 and T4

5. T3 and T4 increase metabolism and support growth and development

6. Thyroid hormones provide negative feedback to reduce further stimulation when hormone levels are adequate

Define primary endocrine disorders

originate in the target gland responsible for producing the hormone (organ itself)

Define secondary endocrine disorder

target gland is essentially normal, but function altered by defective levels of stimulating hormones or releasing factors from the pituitary sytem

Define tertiary endocrine disorders

result from hypothalamic dysfunction; both pituitary and target organ understimulated

What are the findings associated with an increase in growth hormone in adults?

overgrowth of cartilaginous parts of skeleton, enlargement of heart and other organs, metabolic disturbances resulting in altered fat metabolism and impaired glucose tolerance (acromegaly)

What are the findings associated with an increase in growth hormone in children?

causes increased linear bone growth and may result in gigantism

What are the findings associated with a decrease in growth hormone in children?

interferes with linear bone growth, results in short stature or dwarfism

Define thyroid hormone (T3 and T4)

Produced by the thyroid gland; increases metabolism and protein synthesis, influences growth and development in children, mental development and attainment of sexual maturity

Define thyroid stimulating hormone (TSH).

Produced by anterior pituitary. It regulates the function of the thyroid gland and stimulates thyroid hormone production

What conditions are associated with elevated thyroid hormone?

Graves disease, toxic multi nodular goiter, solitary toxic adenoma

When TH is high, what happens to TSH?

inhibits TSH

When TH is low, what happens to TSH?

Stimulates TSH

What are clinical manifestations of hypothyroidism?

• mental and physical sluggishness

• myxedema, somnolence

• dec. cardiac output, bradycardia

• constipation, dec. appetite

• hypoventilation

• cold intolerance

• coarse, dry skin and hair

• weight gain

What are clinical manifestations of hyperthyroidism?

• restlessness, irritability, anxiety, and wakefulness

• inc. cardiac output, tachycardia and palpations

• diarrhea, inc. appetite

• dyspnea

• heat intolerance, increased sweating

• thin and silky skin and hair

• weight loss

What is the pathophysiology of hypothyroidism

• inc. TSH because of low TH

• dec. metabolic rate

• accumulation of hydrophilic mucopolysaccharide substance (myxedema) in the connective tissues

• elevated serum cholesterol

What is the pathophysiology of hyperthyroidism?

• results from excessive TH production and secretion

• inc. metabolic rate and oxygen consumption

• inc. use of metabolic fuels

• inc. sympathetic nervous system responsiveness

What is the pathophysiology of Grave’s disease?

• State of hyperthyroidism; an autoimmune disorder characterized by abnormal stimulation of the thyroid gland by thyroid-stimulating antibodies (thyroid-stimulating immunoglobulins [TSI]) that act through the normal TSH receptors

• associated with human leukocyte antigen (HLA)-DR3 and HLA-B8

What are some symptoms of Grave’s disease?

Goiter, opthalmopathy (bulging eyes), hyperthyroidism

What is the significance of a goiter?

An enlargement of the thyroid gland; in Grave’s disease it reflects abnormal stimulation and overactivity of the thyroid

How do the functions of the adrenal cortical hormones relate to Addison disease (i.e. adrenal insufficiency)?

It is primary adrenal cortical insufficiency, the adrenal cortex does not produce enough hormones. Because of feedback inhibition, ACTH levels are elevated. Can also be secondary adrenal cortical insufficiency which occurs as a result of hypopituitarism or because pituitary gland has been surgically removed

What are the symptoms of Addison disease?

• anorexia and weight loss

• fatigue and weakness

• gastrointestinal symptoms, nausea, diarrhea

• myalgia, arthralgia, abdominal pain

• orthostatic hypotension

• hyponatremia

• hyperkalemia

• hyperpigmentation

• secondary deficiency of select hormones

• associated autoimmune conditions

How do the functions of the adrenal cortical hormones relate to Cushing syndrome?

Caused by excess glucocorticoids, particularly cortisol; Causes may include:

• a pituitary tumor producing excess ACTH

• an adrenal tumor (primary)

• an ectopic ACTH-producing tumor (not common)

What are some symptoms of Cushing disease?

• altered fat metabolism (large abdomen)

• muscle weakness (chicken legs)

• muscle wasting

• purple striae

• osteoporosis

• derangements in glucose metabolism

• hypokalemia/hypernatremia

• gastric acid secretion

• hirsutism, mild acne, and menstrual irregularities

• common cause = long term steroids (organ transplant patients)

Compare symptoms of Cushing disease to side effects of exogenous steroids.

They are essentially the same; produce the exact same clinical manifestations; both result from chronic exposure to excess cortisol