Endocrinology

Cards (61)

  • Endocrine system
    Network of ductless glands that secrete hormones directly into the blood
  • Endocrine system
    • It is considered to be the regulatory hormone of the body
    • It is regulated by means of control of hormone synthesis rather than by degradation
  • Hormones
    Chemical signals produced by specialized cells, secreted into the blood stream and carried to a target tissue
  • Hormones
    • Play an important role in the growth and development of an individual
    • Regulated by metabolic activity either positive or negative feedback mechanism
  • Major function of hormones
    To maintain the constancy of chemical composition of extracellular and intracellular fluids, and control metabolism, growth, fertility and responses to stress
  • Positive feedback mechanism
    A system in which an increase in the product results to elevation of the activity of the system and the production rate
  • Negative feedback mechanism
    A system in which an increased in the product results to decreased activity of the system and the production
  • Types of hormone secretion
    • Endocrine
    • Paracrine
    • Autocrine
    • Juxtracrine
    • Intracrine
    • Exocrine
    • Neurocrine
    • Neuroendocrine
  • Peptide and protein hormones
    • Synthesized and stored within the cell in the form of secretory granules and are cleaved as needed
    • Cannot cross the cell membrane due to their large molecular size and thus produce the effects on the outer surface of the cells
    • They are water soluble and not bound to carrier protein
  • Steroid hormones

    • Lipid molecules that have cholesterol as a common precursor
    • Produced by adrenal glands, ovaries, testes, and placenta
    • Water insoluble (hydrophobic) and circulate bound to a carrier protein
  • Examples of steroid hormones
    • Aldosterone
    • Cortisol
    • Estradiol
    • Progesterone
    • Testosterone
    • Activated vitamin D
  • Amine hormones

    Derived from an amino acid and they are intermediary between steroid and protein hormones
  • Examples of amine hormones
    • Epinephrine
    • Norepinephrine
    • Triiodothyronine
    • Thyroxine
  • Hypothalamus
    • Portion of the brain located in the walls and floor of the third ventricle
    • Above the pituitary gland, and is connected to the posterior pituitary by the infundibulum (pituitary stalk)
    • The link between the nervous system and the endocrine system
  • Anterior pituitary
    • Largest portion of the gland
    • The "true endocrine gland"
    • Regulates the released and production of hormones such as prolactin, growth hormone, gonadotropins (FSH and LH), TSH and ACTH
    • Hormones secreted by the anterior lobe are either peptides or glycoproteins
  • Intermediate lobe

    Little functional capacity
  • Posterior pituitary

    For storage and release of oxytocin and vasopressin
  • Five types of cells in anterior pituitary
    • Somatotrophs
    • Lactotrophs or Mammotrophs
    • Thyrotrophs
    • Gonadotrophs
    • Corticotrophs
  • Growth hormone (somatotropin)

    • Most abundant of all pituitary hormone
    • Controlled by GH-RH (the amount of release) and somatostatin (governs the frequency and duration of secretory pulse)
    • Structurally similar to prolactin and human placental lactogen
    • Secretion is erratic and occurs in short bursts
    • Overall metabolic effect is to metabolize fat stores while conserving glucose
  • Major stimuli for growth hormone
    • Deep sleep (markedly increased GH)
    • Stress
    • Fasting
    • High protein diet
  • Pharmacologic stimuli for growth hormone
    • Sex steroids
    • Apomorphine
    • Levodopa
  • GH suppressors
    • Glucocorticoids
    • Elevated fatty acids
  • Conditions with increased GH
    • Acromegaly
    • Gigantism
    • Chronic malnutrition
    • Renal disease
    • Cirrhosis and sepsis
  • Conditions with decreased GH
    • Hyperglycemia
    • Obesity and hypothyroidism
  • GH deficiency (GHD)
    • Idiopathic Growth Hormone Deficiency is the most common cause in children
    • In children with pituitary dwarfism, normal proportions are retained and show no intellectual abnormalities
    • Pituitary Adenoma is the most common etiology in adult-onset GH deficiency
  • Acromegaly
    Due to overproduction of GH (>50 ng/ml or 2210 pmol)
  • Diagnostic tests for GH deficiency
    • Screening test: Physical Activity Test (Exercise Test)
    • Confirmatory test: Insulin tolerance test (gold standard) or Arginine stimulation test
    • Interpretation: failure of GH to rise >5ng/ml (adults) and >10 ng/ml (child) in all the test is confirmed of GH deficiency
  • Diagnostic tests for acromegaly
    • Screening test: somatomedin C or insulin-like growth factor 1 (IGF-1)
    • IGF-1 is produced in the liver
  • Pituitary Adenoma
    The most common etiology in adult-onset GH deficiency
  • Patient preparation for GH Deficiency test
    Complete rest 30 minutes before blood collection
  • Specimen requirement for GH Deficiency test
    Preferably fasting serum
  • Screening test for GH Deficiency
    Physical Activity Test (Exercise Test)
  • Result of Physical Activity Test
    Elevated serum GH
  • Confirmatory test for GH Deficiency
    1. Insulin tolerance test-gold standard
    2. Arginine stimulation test-2nd confirmatory test
  • Procedure for GH Deficiency test
    24 hour or night time monitoring of GH
  • Interpretation of GH Deficiency test
    Failure of GH to rise >5ng/ml (adults) and >10 ng/ml (child) in all the test is confirmed of GH deficiency
  • GHD in childhood

    Defined by failure of serum GH to reach defined levels when at least two different pharmacologic stimuli are used
  • Screening test for Acromegaly
    Somatomedin C or insulin-like growth factor 1 (IGF-1)
  • IGF-1
    Produced in the liver, increased in patients with acromegaly, low in GHD
  • Confirmatory test for Acromegaly
    Glucose Suppression Test - OGTT (75g glucose)