Endocrine Function PDF

Endocrine Function Pathophysiology Terrel Master, PhD Learning Objectives Compare and contrast Compare and contrast disorders of the pituitary disorders of the thyroid gland gland Hypopituitarism Goiters/nodules Hyperpituitarism...

Endocrine Function Pathophysiology Terrel Master, PhD Learning Objectives Compare and contrast Compare and contrast disorders of the pituitary disorders of the thyroid gland gland Hypopituitarism Goiters/nodules Hyperpituitarism Hypothyroidism Describe and differentiate Hyperthyroidism the types of diabetes Compare and contrast Diabetes mellitus disorders of the adrenal Type 1 Diabetes glands Type 2 Diabetes Pheochromocytoma Gestational Diabetes Cushing Syndrome Addison’s Disease  Endocrine System Overview Endocrine system is a complex messaging and control system Uses hormones secreted by glands located throughout the body Hormones are classified/described in regards to action, source, or chemical structure Hormones can also be divided into four categories based on chemical composition: Steroids Protein or polypeptides Amines and amino acids Fatty acid derivatives Uses a negative and positive feedback system to regulate hormone release Hormones exert action by interacting with target cells on glands and tissues  Pituitary Gland Pituitary gland, referred to as the master gland Roughly the size of a pea, located at the base of the brain Divided into two parts: the anterior and posterior pituitary gland Secretes several hormones: TSH, growth hormone, adrenocorticotropic hormone (ACTH), follicle-stimulating hormone, luteinizing hormone, prolactin melanocyte-stimulating hormone, antidiuretic hormone, and oxytocin Hypopituitarism Rare, complex condition in which the pituitary gland does not produce sufficient amounts of some or all of its hormones (panhypopituitarism) Progressive disorder that can occur suddenly but usually develops slowly Causes: congenital defects, cerebral/pituitary trauma, autoimmune conditions, tuberculosis, pituitary tumors, hemochromatosis, hypothalamic dysfunction Can cause Dwarfism: short stature caused by deficient levels of growth hormone, somatotropin, or somatotropin-releasing hormone Diabetes insipidus: excessive fluid excretion in the kidneys caused by deficient antidiuretic hormone levels Hyperpituitarism The pituitary gland secretes excessive amounts of one or all of the pituitary hormones, most commonly caused by tumors secreting hormone or hormone-like substances Progressive; can occur suddenly but usually develops slowly Can cause Gigantism: tall stature caused by excessive growth hormone prior to puberty Acromegaly: increased bone size caused by excessive growth hormone in adulthood Syndrome of inappropriate antidiuretic hormone: increased renal water retention caused by excessive antidiuretic hormone Hyperprolactinemia: excessive prolactin that results in menstrual dysfunction Cushing’s syndrome: excessive cortisol that results from the increased ACTH levels Hyperthyroidism: hypermetabolic state caused by excessive thyroid hormones from increased TSH  Pancreas Organ with exocrine and endocrine functions Lies underneath the stomach between the two kidneys in the retroperitoneum Endocrine functions are carried out by approximately 1 million islets of Langerhans, Islets of Langerhans cell types: Alpha cells secrete glucagon when serum glucose levels fall Beta cells secrete insulin when serum glucose levels increase and amylin to enhance insulin Delta cells secrete somatostatin, which regulates insulin and glucagon PP cells secrete a pancreatic polypeptide, which regulates some of the other pancreatic activities Epsilon cells secrete ghrelin, which stimulates hunger Diabetes Mellitus (DM) A group of conditions characterized by Complications: hyperglycemia resulting from defects Hyperglycemia in insulin production, insulin action, or Blood glucose above 125 mg/dL both while fasting Impaired insulin production or Glucose toxicity affects blood action results in abnormal carbohydrate, protein, and fat vessels in all your organs, leads to metabolism cardiovascular damage Manifestations: hyperglycemia, Diabetic ketoacidosis DKA glucosuria, polyuria, polydipsia, Without enough insulin, the body polyphagia, weight loss, blurred begins to break down fat as fuel. vision, and fatigue This causes a buildup of acids in the bloodstream called ketones. Types Can lead to organ failure and Type 1 cerebral edema Type 2 Heart disease, stroke, Gestational hypertension diabetic Type 1 Diabetes Insufficient Insulin production Immune system destroys pancreatic beta cells Must take insulin – injections Usually strikes children and young adults, although disease onset can occur at any age Exact cause unknown, but most likely a viral or environmental trigger in genetically susceptible people that causes an autoimmune reaction Cannot be prevented  Prediabetes Blood glucose levels are higher than normal Cells become insulin-resistant, Adipose cells also secrete immune/inflammatory substances that impair insulin sensitivity and glucose metabolism Glucose levels in the blood increase as a result of insulin resistance Causes pancreas to increase insulin production to compensate Hyperglycemia may destroy/desensitize beta cells (glucose toxicity) Lifestyle changes can prevent or delay type 2 DM Diet high in fruits, vegetables, lean meats and whole grains Increased physical activity Type 2 Diabetes Link The pancreas gradually loses its ability to produce insulin Risk factors: advancing age, obesity, family history of DM, physical inactivity Usually managed initially with oral antidiabetic medications that increase insulin production and action As the condition progresses, supplemental insulin is often necessary as pancreatic production declines Gestational Diabetes A form of glucose intolerance diagnosed during pregnancy Treatment usually includes lifestyle changes and insulin Women who have had gestational diabetes have a 40– 60% chance of developing diabetes within 5–10 years About 5–10% of women will be diagnosed with diabetes, usually type 2, immediately following pregnancy Pregnancy Complications: increased fetal weight/size, premature birth, baby has a higher chance of developing type 2 diabetes later in life  Thyroid Gland Located at the base of the neck below the larynx; two lobes, one on either side of the trachea, connected by a thin band of A vascular tissue gland, containing several functional units (follicles) that produce three hormones: Thyroxine (T4), triiodothyronine (T3), and calcitonin T3/T4 (95% of thyroid hormones) regulate cellular metabolism and growth/development Hypothalamus stimulates pituitary gland to produce thyroid-stimulating hormone (TSH), which stimulates T3 and T4 Iodine is required to synthesize thyroid hormones Calcitonin regulates serum calcium levels, inhibiting osteoclast activity (decreases calcium release from the bone) and stimulating osteoblast activity (increases calcium deposits in the bone) Goiters and Thyroid Nodules Visible enlargement of the thyroid gland Usually painless but may affect the respiratory and gastrointestinal systems Dyspnea & Dysphagia Not usually malignant Can occur in hyperthyroidism, hypothyroidism, and normal thyroid states Iodine deficiency is the most common cause worldwide Not common in US Hypothyroidism Hypothyroidism: a condition in which the thyroid does not produce sufficient amounts of the thyroid hormones Relatively common (1 out of 500 Americans has the condition) May be a result of hypothalamus, pituitary, or thyroid dysfunction Most common cause is autoimmune: Hashimoto’s Thyroditis Manifestations: fatigue, increased sensitivity to cold, constipation, pale and dry skin, unexplained weight gain myalgia, arthralgia, muscle weakness, heavier than normal menstrual periods, brittle fingernails, hair loss Bradycardia, hypotension, constipation, depression, and goiter Treatment: thyroid hormone replacement  Hyperthyroidism A condition of excessive levels of thyroid hormones, resulting in a hypermetabolic state Causes: excessive iodine, Graves’ disease, nonmalignant thyroid tumors, thyroid inflammation Manifestations: sudden weight loss, increased appetite, nervousness/irritability, tremor, exophthalmos Diaphoresis, changes in menstrual patterns, increased sensitivity to heat, diarrhea, goiter, tachycardia, hypertension Treatment: radioactive iodine, antithyroid agents, beta blockers, surgery  Adrenal Glands Located superior to each kidney Medulla: inner portion that produces epinephrine and norepinephrine Cortex: outer portion that produces steroids Mineralocorticoids: primarily aldosterone, which acts to conserve sodium and water Glucocorticoids: primarily cortisol, which increases serum glucose levels Gonadocorticoids, or sex hormones: male and female hormones are secreted in minimal amounts in both sexes, but hormones from the testes and ovaries usually mask Pheochromocytoma Rare tumor of the adrenal medulla that excretes epinephrine and norepinephrine; can be life-threatening, Manifestations: hypertension, tachycardia, forceful heartbeat, profound diaphoresis, abdominal pain, sudden onset of severe headaches, anxiety, feeling of extreme fright, pallor, and weight loss Complications: hypertensive crisis, stroke, renal failure, psychosis, and seizures Cause is unknown – can be associated with complex endocrine syndromes or other malignant disorders (renal cell carcinoma) Cushing Syndrome Condition of excessive amounts of glucocorticoids (steroids) Causes: iatrogenic from ingestion of glucocorticoid medications, adrenal tumors that secrete glucocorticoids, pituitary tumors that secrete ACTH and cortisol, and paraneoplastic syndrome Manifestations: obesity (especially around the trunk), Rounding of the face “moon face”, “buffalo hump,” muscle weakness, delayed growth and development acne, purple striae, thin skin that bruises easily, delayed wound healing, osteoporosis, hirsutism, insulin resistance, hypertension, emotional/psychiatric changes Addison’s Disease Adrenal insufficiency Deficiency of adrenal cortex hormones (glucocorticoids, mineralocorticoids, and androgens) Causes: autoimmune conditions, infections, and pituitary dysfunction that results in insufficient ACTH levels Manifestations: hypotension, changes in heart rate, hypoglycemia, chronic diarrhea, hyperpigmentation extreme weakness, fatigue, mouth lesions on the inside of a cheek, nausea, vomiting, salt craving, weight loss, mood changes