Endocrine System Anatomy and Physiology PDF

**ENDOCRINE SYSTEM** **ANATOMY AND PHYSIOLOGY** - Endocrine system is responsible for metabolic activities within the human cells through the release of hormones - Are ductless glands that secrete hormones directly into the surrounding vascular and lymphatic systems or through neuroen...

**ENDOCRINE SYSTEM** **ANATOMY AND PHYSIOLOGY** - Endocrine system is responsible for metabolic activities within the human cells through the release of hormones - Are ductless glands that secrete hormones directly into the surrounding vascular and lymphatic systems or through neuroendocrine processes. - Primary endocrine glands of the body include the pituitary gland, pineal gland, adrenal glands, thyroid gland, parathyroid gland, and thymus gland. - Hormones are synthesized and released in response to three types of stimuli:. (1) humoral stimuli, which involve a direct response to changes in blood chemistry; \(2) neural stimuli, such as in the case of the adrenal glands secreting epinephrine or norepinephrine in response to the sympathetic nervous system; and \(3) hormonal stimuli, which involve a response to other hormones secreted in the body. - The pituitary gland comprises three separate lobes: \(1) the anterior lobe, \(2) the intermediate lobe, \(3) the posterior lobe. - The pituitary is considered the "master endocrine gland," and it is located below the hypothalamus at the base of the brain within the sella turcica of the sphenoid bone - The pineal gland is also controlled by the hypothalamus. It is located within the cranium, posterior to the third ventricle, superior to the colliculi of the midbrain, and inferior to the splenium of the corpus callosum - The adrenal glands are pyramid-shaped glands located on the upper poles of the kidneys - The inner portion of the adrenal gland, termed the adrenal medulla, acts as a part of the sympathetic nervous system and secretes the catecholamines epinephrine and norepinephrine - The adrenal cortex activity is primarily controlled by ACTH, which is secreted by the anterior pituitary. - ACTH synthesizes three major types of corticosteroids: \(1) mineralocorticosteroids, which are responsible for electrolyte balance; \(2) glucocorticoids,which are responsible for cell metabolism and for controlling blood sugar levels; and. (3) low levels of gonadocorticosteroids or sex hormones. Mineralocorticoids such as aldosterone may affect extracellular fluid volume and blood volume, which ultimately affects blood pressure and cardiac output. - The thyroid gland is located in the anterior neck just below the larynx - The thyroid gland is vital to maintaining normal blood pressure and in regulating tissue growth and development. - Overactivity of the thyroid gland is termed [hyperthyroidism], and underactivity is termed [hypothyroidism]. - The parathyroid glands are located on the posterior aspect of the thyroid gland. \- they are responsible for producing and secreting PTH, which also serves to control blood calcium levels. - The pancreas is located in the midabdomen just posterior to the stomach and functions both as an endocrine organ and an exocrine organ. - The tail of the pancreas ends at the spleen, and the head is encircled by the duodenum. - Specialized cells within the pancreas, termed the islets of Langerhans or pancreatic islets, -. -responsible for the production of important hormones. - The α-cells are responsible for glucagon synthesis; the β-cells are responsible for balancing the secretion of insulin and glucagon, depending on food intake; and the δ-cells are responsible for secreting somatostatin, a hormone which influences the secretion of the α-cells and β-cells. **IMAGING CONSIDERATIONS** **RADIOGRAPHY** - Radiographic examination is very helpful in diagnosing metabolic diseases of the skeletal system or endocrine disorders that ultimately affect the skeletal system, for example, Cushing disease. - Skull radiography is of limited use in evaluating metabolic disorders of the pituitary gland Increasingly being replaced by Magnetic Resonance Imaging (MRI), Computed tomography (CT), or position emission tomography (PET) in making a definitive diagnosis bfor pituitary disorders **[BONE MINERAL DENSITOMETRY]** - Dual-energy x-ray absorptiometry (DXA) or bone mineral densitometry is an important modality in the evaluation of osteoporosis. - DXA units readily show bone density by evaluating the bone mass of the distal radius, femoral neck, and lumbar spine. - Bone densitometry are used in combination with routine laboratory tests of blood and urine to determine loss of bone mass. - Bone mineral densitometry reports indicate the amount of bone mass present and compare the density of a particular individual to norms used in evaluation **[MAGNETIC RESONANCE IMAGING]** - Largely replaced CT for imaging neuro-endocrine disorders. - According to the American College of Radiology (ACR), MRI is the only imaging modality that can reliably demonstrate pathologies of the hypothalamus. - Pituary disorders often result in an enlarged sella turcica, represented by the "empty sella syndrome", which can be confirmed with MRI. - MRI is also helpful in monitoring the progress of patients with pituitary adenomas **[COMPUTED TOMOGRAPHY]** - May also be used in the diagnosis and follow-up care of patients with pituitary disorders. - It is frequently used when MRI is not available or may be contraindicated - CT examinations of the neck are useful in the evaluation of neoplastic disease of the thyroid and parathyroid glands. - Abdominal CT is used in assessing enlargement of the adrenal glands of patients with Cushing disease. **[NUCLEAR MEDICINE PROCEDURE]** - used to detect nonpalpable nodules and to evaluate the remaining thyroid tissue after surgical resection or ablation. - The use of nuclear medicine imaging to localize medullary tumors in the adrenal glands using iodine -131 metaiodobenzylguanidine(MIBG). - This radioisotope may also be used to treat tumor of the medullary portion of the adrenal gland. **SKELETAL DISORDER** **[OSTEOPOROSIS]** - A commonly known metabolic bone disorder in which the structural integrity of the trabecular pattern of bone is destroyed - Identified as a bone mass less than 648 mg/cm2 - It may be classified as primary osteoporosis (type1) or secondary osteoporosis (type2) - Primary osteoporosis may be further classified as postmenopausal or senile, -Postmenopausal osteoporosis is the most common form of the disease. -In postmenopausal women, for example, the lack of the hormone estrogen creates a weakened bone matrix, contributing to the development of "porous" bones. -As the condition becomes more severe, bones are subject to compression fractures, and they may literally cave in from the weakness.. -Osteoporosis is a subtractive or destructive pathologic condition and requires a decrease in exposure technique. -The best method for evaluating the early stages of osteoporosis is bone mineral densitometry of the hip and lumbar spine using DXA - Secondary osteoporosis is most commonly associated with an existing disease process or is the result of a medication. -Secondary osteoporosis may be caused by other diseases -Osteoporosis is, by far, the most common form of metabolic bone disease and can be differentiated from other causes of bone weakening by examining serum enzyme levels, especially alkaline phosphatase. \- Treatment of osteoporosis generally includes an increase in dietary intake of calcium, vitamin D and magnesium in combination with moderate weight- bearing exercise. **[OSTEOMALACIA]** - A condition caused by lack ofcalcium in tissues and failure of bone tissue to calcify. - Osteomalacia may be associated with hepatic disease, chronic pancreatitis, regional ileitis, and resections of the GI system because these conditions may inhibit the body from absorbing fat-soluble vitamin D. - If osteomalacia occurs before growth plate closure, it is known as rickets - With this condition, the bones are spongelike and demonstrate osteopenia on radiographic evaluation - Radiographically, osteomalacia appears similar to osteoporosis except for the presence of bands of radiolucency within the bone, termed pseudofractures or Looser zones. - Bone biopsy and measurement of serum fibroblast growth factor 23 (FGF-23) levels are the definitive methods of determining the presence of osteomalacia - This disorder may be treated by adjusting serum calcium and phosphate levels, inclusion of a dietary supplement of vitamin D,administering calcium carbonate, chelating bone aluminum, renal dialysis **[PAGET'S DISEASES]** - A metabolic disorder of unknown cause; however, recent research indicates a genetic link and the possible role of viral infectious agents. - It usually begins in the fifth decade of life and may affect one or more bones, most commonly the pelvis, spine, skull and long bones - Paget disease is characterized by two stages: \(1) the osteolytic stage,in which the bone undergoes continuous destruction, and \(2) the osteoblastic stage, in which bone is simultaneously replaced by abnormally soft and poorly mineralized material - As the skull enlarges, additional complications may occur because of impingement on the cranial nerves. These complications include hearing and vision disturbance - In addition, individuals with Paget disease have an increased risk of developing osteogenic sarcoma, a malignant neoplastic disease of the skeletal system - No known cure exists for this disease. **PITUARY GLAND DISORDERS** **[ACROMEGALY]** - Acromegaly is an endocrine disorder caused by a disturbance in the function of the pituitary gland; this disorder primarily affects the skeletal system. - More common in females than in males and most frequently occurs in individuals over age 40 years. - This disorder is caused by excessive secretion of GH in adults, which is often the result of a pituitary adenoma. - Radiographic studies demonstrate an enlarged sella turcica and changes in the skull, often obliterating the diploë found between the inner and outer tables of cortical bone. - Individuals with acromegaly have a prominent forehead and jaw, widened teeth, abnormally large, spadelike hands and a coarsening of facial features - This disorder is frequently treated with a combination of surgery and radiotherapy to eradicate the adenoma. - Although this is slowly progressing disease, it may lead to premature death from associated cardiovascular and renal complications if it is not treated. **[HYPOPITUITARIANISM]** - the decreased level or absence of pituitary hormones originating from the anterior pituitary gland. - Most common causes of this disorder are embryonic mutations of the prophet of pituitary transcription factor gene (PROP-1) or pituitary infarction - May also be associated with infarction caused by pregnancy (Sheehan syndrome), postpartum hemorrhage, shock, sickle cell disease, meningitis, syphilis, or head trauma. - Treatment includes hormone replacement **ADRENAL GLAND DISORDERS** **[CUSHING SYNDROME]** - Results from a dysfunction within the adrenal cortex leading to hypersecretion of glucocorticoids from the anterior pituitary - Individuals with this disorder tend to have round, "moon" facies, with excess fat deposits in the neck and trunk regions of the body - The patient's skin is thin and does not heal well after injury. Female patients tend to have male characteristics because of an increased production of androgens, and their menstrual cycles are usually quite irregular - Treatment of Cushing syndrome depends on the point of origin, - In some cases, radiotherapy may be used to treat pituitary adenomas, or surgical resection of the adrenocortical tumor may be required. - If the condition is not treated, over half of the individuals with Cushing syndrome die within 5 years. **[ADDISON DISEASE]** - a rare disease of primary adrenal insufficiency - most frequently affects women between ages 30 and 60 years - it caused by infection , neoplastic disease or adrenal hemorrhage - This disease characterized by elevated ACTH accompanied by inadequate corticosteroid synthesis - Signs and symptoms include weight loss, fatigue, weaknesses, nausea, diarrhea, low blood sugar and low blood pressure leading to hypotension - Treatment includes use of HRT in combination with a special diet **[ADRENAL CARCINOMA]** - Are quite rare, but other types of cancers often metastasize to the adrenal glands. - Lung cancers are the most common types of adrenal metastatic cancers, - Contrast enchanced CT and MRI studies are helpful in the diagnosis of adrenal masses - The risk of malignancy increases as the size of the tumor increases, so most masses are surgically removed **PANCREATIC DISORDERS** **[DIABETES MELLITUS]** - A syndrome that is associated with chronic hyperglycemia in combination with glucose intolerance and alterations in the metabolism of carbohydrates, fats, and proteins. - Normal blood glucose levels range from 70 to 120 milligrams per deciliter (mg/dL), and fasting glucose levels greater than 126 mg/dL indicate the presence of this syndrome. - The most common types of diabetes mellitus are type 1, caused by a defect in the primary β cells, and type 2, resulting in insulin resistance **[TYPE 1 DIABETES MELLITUS]** - Type 1 diabetes mellitus appears to be a genetic disorder, and it is one of the most common diseases in childhood - Type 1 diabetes can be further classified as type 1A and type 1B; \- type 1A is an autoimmune variation of the disease and is more common than type 1B. \- Type 1B is believed to be nonimmune in nature and generally occurs secondary to other pathologic processes -Type 1A diabetes is associated with a histocompatibility leukocyte antigen (HLA) marker, which has also been linked to other autoimmune endocrine diseases such as Graves and Addison diseases**.** - Type 1 diabetes mellitus is often referred to as juvenile diabetes because most cases manifest before age 30 years. - Signs and symptoms of type 1 diabetes mellitus include weight loss, fluctuations in blood glucose levels, increased urination, excessive thirst, and an increased appetite. - The goal of treatment is to adequately control glucose levels without causing hypoglycemia. - Treatment is varied and may include the use of immunosuppressive drugs, immunomodulation therapies, careful meal planning, exercise, and blood glucose checks multiple times per day in combination with daily insulin injections. **[TYPE 2 DIABETES MELLITUS]** - Characterized as insulin-resistant diabetes with an inadequate secretion of insulin. - Much more common than type 1 in the United States, and the incidence of type 2 diabetes has doubled over the past 15 years. - Genetic susceptibility in combination with environmental factors is suspected to be the cause of this disease - Recently the medical community has identified metabolic syndrome as a precursor to type 2 diabetes mellitus. - Metabolic syndrome is classified in individuals demonstrating three of the following five traits: **(1) waist circumference greater than 40 inches in males and greater than 35 inches in females** **(2) triglycerides 150 mg/dL or more** **(3) high-density lipoprotein (HDL) cholesterol less than 40 mg/dL in males and less than 50 mg/dL in females** **(4) blood pressure 130/85 mm Hg or greater** **(5) a fasting plasma glucose 100 mg/dL or greater.** - It is important to note that not all individuals with metabolic syndrome will develop type 2 diabetes mellitus - The diagnosis and treatment of type 2 diabetes mellitus are similar to those for type 1 **PARATHYROID GLAND\ DISORDERS** **[HYPERTHYROIDISM]** - Most frequently caused by an autoimmune disorder termed Graves' disease. - In this disorder, the body creates antibodies that fight the thyroid TSH receptor, causing the thyroid gland to secrete excess amounts of this hormone. - More common in females than in males, and a combination of genetic and environmental factors are linked to this disease - Symptoms of this chronic disorder include an enlarged thyroid gland or goiter and changes to the eyes and skin.\ Left untreated, hyperthyroidism may result in a critical event termed a thyroid storm, which is a life-threatening situation and must be treated within 48 hours. - Treatments include antithyroid drugs, surgical resection of the thyroid gland and most commonly the administration of radioactive iodine. **HYPOTHYROIDISM** - a common disorder of the thyroid gland and results from a deficiency of TH. - This disorder has many causes and can affect individuals of any age or gender. However, primary hypothyroidism most commonly affects women over age 60 years. - Hypothyroidism may also be iatrogenic in nature, resulting from treatment of a goiter through radioactive iodine therapy or surgical intervention. - Signs and symptoms of hypothyroidism occur slowly over many months and include a decreased energy level, cold intolerance, personality changes, and modest weight gain. - Treatment generally improves HRT with synthetic hormones. **THYROID CANCERS** - Although most neoplasms of the thyroid gland are benign, four types are malignant,. - Cancers of the thyroid are more common in younger individuals and in females - Signs and symptoms of thyroid cancers include changes in voice and symptoms resulting from compression of the esophagus such as dysphagia, or compression of the trachea. - Diagnosis is made using a nuclear medicine - The most common treatment is the surgical removal of the thyroid gland followed by the administration of radioactive iodine to ablate any remaining thyroid tissue and medication to suppress production of TSH. **HYPERPARATHYROIDISM** - A fairly common disease of the endocrine system that affects the skeletal system. - This disease is often very mild and may go undetected for a long time. - Hyperparathyroidism applies to any disorder that disrupts the calcium--phosphate ratio and results in an elevated level of PTH. - Three types of hyperparathyroidism are: - Primary hyperparathyroidism most frequently affects adults in their 30s or 50s and arises from an adenoma , carcinoma, or hyperplasia of the parathyroid gland. - Secondary hyperparathyroidism represents a response to hypocalcemia, hyper-phosphatemia, or hypomagnesemia **NEPHROCALCINOSIS** - disturbances of calcium metabolism, as in hyperparathyroidism, may result of nephrocalcinosis - a condition that is characterized by tiny deposits of calcium phosphate dispersed throughout the renal parenchyma - Calcium may also be deposited throughout the parenchyma as a result of tissue damaged by some other disease process or injury. - Treatment designed to lower serum calcium levels is also important.