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• Hormones


  Organic compounds produced by the endocrine system and secreted directly into the blood to act near to their site of release or at a distant organ in the body
• General functions of hormones

  • Regulation of metabolism
  • Growth
  • Homeostasis
  • Behaviour
  • Reproduction
• Classification of hormones by chemical composition

  • Amino acid derivatives (e.g. thyroid hormones, epinephrine, norepinephrine, serotonin)
  • Polypeptides (e.g. pituitary hormones like oxytocin, ADH, ACTH)
  • Proteins and glycoproteins (e.g. insulin, growth hormone, TSH, LH, FSH, parathyroid hormone, prolactin)
  • Steroids (e.g. adrenal cortical hormones, sex hormones like estrogens, progesterone, androgens)
• Classification of hormones by mechanism of action

  • Group 1: Bind to intracellular receptors
  • Group 2: Bind to cell surface receptors
• Hypothalamus


  Part of the central nervous system located at the base of the brain just above the pituitary gland, secretes releasing hormones, vasopressin (ADH) and oxytocin

  
• Hypothalamic releasing hormones


  • Corticotropin-releasing hormone (stimulates ACTH release)
  • Thyrotropin-releasing hormone (stimulates TSH and prolactin release)
  • Growth hormone-releasing hormone (stimulates GH release)
  • Somatostatin (inhibits GH, gastrin, glucagon, insulin, TSH, prolactin release)
  • Gonadotropin-releasing hormone (stimulates FSH and LH release)
  • Dopamine (inhibits prolactin release)
• Pituitary gland


  Often called the "master gland" as its hormones control other endocrine glands
• Anterior pituitary hormones


  • ACTH (stimulates adrenal glands)
  • GH (essential for growth and healthy body composition)
  • FSH (ensures normal ovary/testes function with LH)
  • LH (ensures normal ovary/testes function with FSH)
  • Prolactin (stimulates breast milk production)
  • TSH (stimulates thyroid gland)

  
• Posterior pituitary hormones


  • ADH (increases water absorption in kidneys)
  • Oxytocin (involved in childbirth, breast milk production)
• Types of pituitary tumors


  • Secretory (secrete excess hormone)
  • Non-secretory (don't secrete excess hormone)
• Pituitary apoplexy


  Sudden disruption of pituitary function due to bleeding or trauma, can be life-threatening
• Disorders from pituitary hormone overproduction

  • Acromegaly/gigantism (excess GH)
  • Cushing's disease (excess ACTH)
  • Galactorrhea (excess prolactin)
  • Erectile dysfunction (excess prolactin)
  • Infertility (excess prolactin)
• Disorders from pituitary hormone underproduction

  • Dwarfism (lack of GH)
  • Central diabetes insipidus (lack of ADH)
  • Hypopituitarism (lack of multiple hormones)
• Thyroid hormones


  Thyroxine (T4) and triiodothyronine (T3), formed by adding iodine to tyrosine in thyroglobulin
• Functions of thyroid hormones

  • Increase metabolism and heat production
  • Regulate growth of long bones (with GH)
  • Stimulate protein synthesis
  • Increase catecholamine effects
• Goitre


  Enlargement of the thyroid gland, may cause difficulty breathing/swallowing, can have normal, decreased or increased thyroid function
• Hypothyroidism


  Insufficient thyroid hormone (T3, T4) production, can be due to thyroid, pituitary or hypothalamic disease, causes symptoms like fatigue, weight gain, cold intolerance, constipation
• Hyperthyroidism (thyrotoxicosis)


  Excessive thyroid hormone (T3, T4) production, most commonly due to Graves' disease (antibodies activating TSH), can also be from toxic multinodular goitre or thyroiditis, causes symptoms like exophthalmos, sweating, tachycardia, weight loss, tremor
• Adrenal glands


  Small triangular glands located on top of each kidney, consist of an outer cortex and inner medulla
• Hyperthyroidism


  Excessive production of thyroid hormones
• Hyperthyroidism


  • Most patients have an enlarged thyroid gland (goitre)
  • Most cases are due to Graves disease which results from the production of antibodies that activate TSH production and in turn produces excessive amounts of T3 and T4
  • These antibodies are called: Thyroid-stimulating IgG (TSI)
  • Also, sometimes due to toxic multinodular goitre (Plummer disease), and thyroid inflammation (thyroiditis)
• Hyperthyroidism symptoms and signs

  • Exophthalmos (protrusion of eye ball)
  • Excessive sweating
  • Heat intolerance
  • Tachycardia
  • Hypertension
  • Fatigue
  • Weakness
  • Weight loss
  • Tremor (usually fine shaking)
  • Nervousness, agitation, anxiety
  • Pretibial myxedema (nodular lesion over the anterior aspect of lower legs)
• Adrenal glands


  Small, triangular glands located on top of each kidney (one on each side)
• Adrenal gland


  • Outer region called the adrenal cortex
  • Inner region called the adrenal medulla
• Hormones of adrenal cortex

  • Glucocorticoids
  • Mineralocorticoids
  • Androgens
• Steroid hormones

  All contain steroid ring and derived from cholesterol
• Major steroid hormones secreted by the human adrenal cortex

  • Cortisol
  • Corticosterone
  • Aldosterone
  • Dehydroepiandrosterone (DHEA) sulphate
• Cushing's syndrome


  Overproduction of glucocorticoids
• Cushing's disease


  • Occurs when a person is exposed for a long time to high levels of adrenal glucocorticoids (cortisol)
  • Results in hyperglycaemia, High blood pressure, Weight gain and fat distribution mostly in the abdominal region, Poor wound healing, High blood pressure, Irritability, anxiety, mood swings, and/or depression
  • May occur if the person takes high dose steroids to treat other problems, such as rheumatoid arthritis, inflammatory bowel disease, lupus, and severe asthma
  • In some cases, a tumor on the pituitary gland, which stimulates the adrenal glands to produce cortisol, can lead to Cushing's disease
• Adrenal insufficiency (Addison's syndrome)

  Underproduction of glucocorticoids
• Primary adrenal insufficiency


  • Results from the destruction of the adrenal cortex, and usually an autoimmune condition in which a patient's immune system uses its antibodies to attack and destroy its own adrenal glands
  • Some less common causes include: Tuberculosis, adrenal tumors and other infections
• Secondary adrenal insufficiency


  More common form and is due to a lack of adrenocorticotropin (ACTH) which stimulates the adrenal glands to produce cortisol
• Adrenal insufficiency results in hypoglycemia, anoroxia, weight loss, intolerance to stress and severe weakness
• Conn's syndrome


  Overproduction of mineralocorticoids
• The classical manifestations include hypertension, hypokalemia, hypernatremia and alkalosis
• Adrenal cancer (primary adrenal carcinoma)

  Rare, aggressive form of cancer in which cancer cells are found in the adrenal cortex, the outside layer of the adrenal gland
• Adrenal incidentaloma


  Adrenal cancer
• Hormones of adrenal medulla

  • Epinephrine
  • Norepinephrine
  • Dopamine
• Pheochromocytomas


  Tumors that develop in the adrenal medulla, which can cause overproduction of catecholamines
• Excess of catecholamines causes high blood pressure in most of the cases