Endocrine System


Terms in this set (...)

Endocrine glands secrete
chemical messengers called hormones
Circulate in the blood and can affect a single target organ or the whole body
Hormones may be
proteins, steroids, peptides, amino acids, or amines
Major endocrine glands are
pituitary, adrenal, thyroid, and parathyroid glands
Negative feedback mechanism
An adequate level of hormone in the blood automatically stops the release of additional hormone
As the level decreases the gland is stimulated to secrete more of it
Another control mechanism
Production of 2 different hormones whose actions are opposite of eachother
Example, insulin and glucagon
Adrenal glands consist of
Outer cortex and an inner medulla
Adrenal cortex secretes
steroid hormones and can be divided into 3 groups
Primarily aldosterone
Regulate salt and water balance by controlling sodium retention and potassium excretion by the kidneys
Production of aldosteone
Regulated primarily by the secretion of renin from specialized cells in the kidney
Especially cortisone
Regulate carbohydrate metabolism
Depresses the inflammatory response to almost all forms of injury
Glucocorticoids or cortisone are regulated by
Adrenocorticotrophic hormone (ACTH) from the anterior pituitary gland
Sex hormones that tend to masculinize the body, retain amino acids, and enhance protein synthesis
Adrenal medulla secretes
epinephrine (adrenaline) and norepinephrine
Fight or flight hormones
Epinephrine stimulates
heart activity, raises blood pressure, increases the level of blood glucose, shunts blood to active muscles where oxygen and nutrients are needed
Diseases of Adrenal Cortex
Cushings Syndrome
Androgenital Syndrome
Adrenal carcinoma
Metastases to adrenal gland
Cushings Syndrome
Excess production of glucocorticoid hormone
Characteristic obesity in their trunk of body, round moon shaped face, and fat pad behind their shoulders
Best demonstrated with CT
Overproduction of mineralocorticoids produced in the cortex
Causes retention of sodium and water and abnormal loss of potassium in the urine
Results in hypertension, muscluar weakness or paralysis, and polydipsia (excessive thirst)
May be attributable to Conns syndrome (adrenocortical adenoma)
Basis for diagnosing is biochemical assay and CT is used used to locate them
Adrenogenital Syndrome
Adrenal Virlism
Excessive secretion of androgens by the cortex
Congenital form there is an enzyme deficiency that prevents androgens formation and continuous ACTH stimulation
Elevated levels of androgens result in accelerated skeletal maturation with premature epiphyseal fusion which can lead to dwarfism
In women it causes masculinization, hair on the face (hirsutism)
Most are caused by adrenocorticocal tumors
Detected by CT
Adrenal insufficiency
Chronic insidious disorder (fatigue, anorexia,weight loss, weakness)
Acute collapse with hypotensionm rapid pulse, vomitting, diarrhea
Most common cause is excessive steroid use
Addisons Disease
Primary adrenocortical insufficiency
Results from progressive cortical destruction
More than 90% destruction of gland before clincal signs appear
Adrenal Carcinoma
About half of adrenal carinomas are functional tumors
Tumors grow rapidly and are usually necrotic masses
CT is best modality
Lymphatic and hepatic mets are common
Metastases to the Adrenal Glands
One of the most common sites of metastatic disease
Primary tumors that most frequently metastasize to the adrenals are carcinomas of lung, breast, kidneys, ovaries, GI tract, and melanoma
Causes downward displacment of the kidney with flattening of the upper pole
Ultrasound and CT demonstate the mets
Diseases of the Adrenal Medulla
Tumor of the adrenal medulla
Produces an excess of vasopressor substances (epinephrine and norepinephrine) which causes hypertension
10% are extra adrenal, 10% are bilateral, and 10% are malignant
Diagnosis is with biochemical tests and imaging is for location and confirmation
Ultrasound and CT are used
Appear as round, oval, pear shaped masses
Necrosis, hemorrhage, fluid levels are common in larger lesions
Can be located anywhere along the sympathetic nervous system
Arterial injection of contrast causes sharp elevation in BP
Most tumors are benign
Tumor of adrenal medulla
Second most common malignancy in children
10% arise outside of adrenal gland
Highly malignant
Calcification is common with a fine, granular, or stippled appearance
Calcification can also happen in the mets of a neruoblastoma in the lymph nodes or liver
Downward and lateral renal displacement by the tumor
Whole kidney is displaced unlike Wilms tumor
Ultrasound is the best in children
CT is most commonly used to study to diagnose neuroblastoma because of its spread (mets)
Mets to bone, liver, and lungs are common
What is the master gland?
Pituitary Gland
What controls the pituitary gland?
Pituitary anatomy
Sits in the sella turcica, suspended from the base of the brain by the infundibulum, and divided into anterior and posterior portions
Anterior Lobe secretes
Affects all parts of the body
Promotes growth and development of tissues
Before puberty it promotes long bone growth and size of liver and kidneys and heart
After adolesence it continues in lesser amounts to function as replacement and repair
Secretion of thyroid hormone
Regulates the bodys metabolism
Controls levels of activty in the adrenal cortex
posterior lobe of pituitary
2 hormones
Vasopressin (ADH)
Increases rate of reabsorbtion of water and electrolytes by renal tubules and devreasing urine output
Contraction of smooth muscle especially in the uterus
Diseases of the Pituitary gland
Diabetes Insipidus
Excess of GH produced by a tumor
Generalized hyperplasia of anterior lobe
Before enchondral bone growth is gigantism
After bone growth has stopped is acromegaly
Generalized overgrowth of all body tissues is the underlying abnormality in acromegaly
Bones in hands, feet, and face enlarge and excessive growth of soft tissues
Acromegaly has joint spaces that are normal or even widened
Increased disk space in L spine and scalloping
Gigantism is an excessively large skeleton
Diagnosis of a pituitary tumor
Decreased function of pituitary
Disturbances in bone growth and maturation
In children it lead to dwarfism, well proportioned and normal mentaility but delayed appearance of epiphyseal centers and failure of bone growth
In adults there is hypofunction of the thyroid, adrenal, and gonads but few radiologic findings
Heart and kidneys are small and calcifications or ossifications may developin articular cartilages
MRI is preferred
Diabetes Insipidus
Impaired ability of the kidneys to conserve water
Low blood levels of ADH from low levels of vassopressin release from post. pituitary
Polyuria (excessive water loss in urine)
Polydipsia (excessive thirst)
Another type is when kidneys fail to respond to circulating ADH and is known as nephrogenic diabetes insipidus
These types are completely unrelated to diabetes mellitus