305 endocrine

• Hormones


  Chemical messengers
• Hormones


  • Can work on distant cells
  • Can work on nearby cells (paracrine)
  • Can work on itself (autocrine)
  • Affects all body systems/organs as they are controlled or influenced by some hormone
• Bound Hormone


  Transported through protein carriers
• Free Hormone


  Needs to be free to send the message to the target tissue
• Hormone Alterations


  • Deficiency: due to autoimmunity, infection, inflammation, infarction, tumor
  • Excess: tumor, autoimmunity, genetic mutation
  • Resistance: causing dysfunctional receptor sites
• Hypothalamus-pituitary-hormone axis


  1. Primary: at the site of the gland

  2. Secondary: Pituitary

  3. Tertiary: Hypothalamus
• Tropic hormone


  A hormone that controls the biosynthesis and secretion of hormones from other target endocrine glands
• Negative feedback

  Causes inhibition of release
• Positive feedback

  Causes more to be released
• Down Regulation


  • Prolonged, excessive stimulation of the endocrine system
  • Leads to decrease in number of receptor sites
  • Receptor insensitivity
  • System is depleted; hormone cannot cause desired effects
• Example: taking excessive steroids
• Hypothalamus


  Hypothalamic hormones regulate the synthesis and secretion of pituitary gland hormones
• Anterior Pituitary Gland Hormones

  • Growth Hormone (GH)
  • Thyroid Stimulating Hormone (TSH)
  • Adrenocorticotropic Hormone (ACTH)
  • Follicle Stimulating Hormone (FSH)
  • Luteinizing Hormone (LH)
  • Prolactin
  • Melanocyte-Stimulating Hormone (MSH)
• Posterior Pituitary Gland Hormones

  • Antidiuretic Hormone (ADH)
  • Oxytocin
• Hypopituitarism


  Decreased secretion of anterior pituitary gland hormones
• Causes of Hypopituitarism


  • Congenital
  • Destruction of anterior pituitary
  • Deficiency of hypothalamic hormones: due to stress, change in body weight, anorexia, bulimia, heart failure
• Hyperpituitarism


  Oversecretion of anterior pituitary gland hormones
• Causes of Hyperpituitarism


  • Pituitary Adenomas
  • Hypothalamic lesions
• Antidiuretic Hormone (ADH)


  • Synthesized by hypothalamus, stored and secreted by posterior pituitary
  • Essential to maintain body's fluid balance through reabsorption of water by the kidneys
  • Anti-urine production
• Diabetes Insipidus


  • Decreased ADH secretion or renal response to ADH resulting in excess water loss
  • Fails to concentrate urine
• Clinical Manifestations of Diabetes Insipidus

  • Extreme thirst
  • Dehydration
  • Polyuria
  • Enuresis (bed wetting)
  • Hypernatremia
  • Pee a lot
• Causes of Diabetes Insipidus


  • Neurogenic (Central): Diseases that affect hypothalamic-neurohypophyseal system, Head injury, Brain surgery, Gestational
  • Nephrogenic: Congenital, Pyelonephritis, Lithium toxicity, Electrolyte disorders, Chronic hypercalcemia, Hypokalemia
• Syndrome of Inappropriate Antidiuretic Hormone (SIADH)

  Failure for negative feedback system to regulate ADH resulting in excess water retention (too much ADH)
• Clinical Manifestations of SIADH

  • Water retention/intoxication
  • Dilutional hyponatremia (diluted blood)
  • Muscle cramps/weakness
  • N/V/D
  • Lethargy, disorientation, HA
  • Confusion, depression of DTR
  • Seizures, coma
  • Decreased urine output; concentrated urine
  • Don't pee enough
• Causes of SIADH


  • Surgery, trauma, tumors secreting ADH
  • Pain/stress
  • Temperature changes
  • HIV
  • Intrathoracic conditions (pneumonia, ventilation)
  • Conditions that affect CNS: Hydrocephalus, Head injury, Encephalitis
• Growth Hormone


  • Essential for growth
  • Peak levels secreted occurs after onset of sleep
• Increased Secretion of Growth Hormone


  • Gigantism: Excess of GH before puberty and fusion of long bones, Increased height
  • Acromegaly: GH excess after puberty and fusion of long bones, No increase in height, Soft tissues continue to grow, Bones in hands, feet, & face continue to grow (small bones), Muscles continue to grow
• Decreased Secretion of Growth Hormone in Children


  • Causes: Abuse/Neglect, Pituitary Tumors, Agenesis of Pituitary
  • Clinical Manifestations: Normal intelligence usually but can have mental retardation or minor learning disabilities, Short stature or dwarfism, Obesity with immature facial features, Delay in skeletal maturation, Delayed puberty, Microphallus in males
• Decreased Secretion of Growth Hormone in Adults

  • Causes: Preexisting from childhood, Pituitary tumor, Treatment of pituitary tumor
  • Clinical Manifestations: Decrease in lean body mass, Increase in fat mass, Decreased bone mineral density, Reduced exercise capacity, Diminished sense of well-being
• Thyroid


  • Butterfly-shaped structure located immediately below the larynx in the anterior middle portion of neck (not normally palpable)
  • Efficient in use of iodine
  • Thyroid hormones (T3 & T4) regulate growth and development of children, metabolism and protein synthesis, cardiovascular and respiratory functions, GI motility, neural control of muscle function and tone
• Thyroid Tests


  • TSH (precursor/tropic hormone): Test to differentiate between primary or secondary thyroid disorders (thyroid prob. vs anterior pituitary problem)
  • T3 (Triiodothyronine): Active form of hormone, Measures amount of T3 available
  • T4 (Thyroxine): Body metabolism regulator, Has to be converted to T3 to be used, Measures how much T4 is available
• Hypothyroidism


  Decreased secretion of thyroid hormones
• Causes of Hypothyroidism


  • Congenital
  • Thyroidectomy
  • Ablation of thyroid
  • Medications
  • Iodine Deficiency
  • Hashimoto thyroiditis (autoimmune disorder)
• Clinical Manifestations of Hypothyroidism


  • Slows metabolism
  • Weight gain
  • Myxedematous features
  • Impaired growth in children
  • Mental sluggishness
  • Decreased cardiac output
  • Constipation (from decreased gastric metabolism)
  • Cold intolerance
  • Decreased sweating
  • Dry, coarse hair and skin
• Myxedema Coma


  • End stage hypothyroidism or severe hypothyroidism
  • Pathophysiology: Carbon dioxide retention and hypoxemia, Fluid and electrolyte imbalance, Hypothermia
• Clinical Manifestations of Myxedema Coma

  • Coma
  • Hypothermia
  • Cardiovascular collapse
  • Hypoventilation
  • Hyponatremia
  • Hypoglycemia
  • Lactic acidosis
• Hyperthyroidism


  Hypersecretion of thyroid hormones
• Causes of Hyperthyroidism


  • Grave's Disease (autoimmune disorder)
  • Thyroid tumor
  • Diffuse goiter (does not always cause dysfunction of thyroid)
• Clinical Manifestations of Hyperthyroidism

  • Weight Loss
  • Increased appetite
  • Exophthalmos
  • Muscle shakes
  • Thin, silky hair and skin
  • Tachycardia and palpitations, dysrhythmias
  • Nervousness, anxiety
  • Irritability
  • Fatigue
  • Heat intolerance
  • Tachypnea, Dyspnea
  • Excessive sweating
• Thyroid Storm


  • Precipitating Factors: Infection, Stress, Diabetic Ketoacidosis, Trauma, Manipulation during thyroidectomy
  • Clinical Manifestations: Tachycardia, angina, dysrhythmias fatal, Extreme hyperthermia, Agitation, restlessness, Delirium, coma, Hepatomegaly with jaundice, Weakness with muscle wasting
  • Extreme and life-threatening form of thyrotoxicosis
  • Mortality rate is high