PMS II - Exam 1

• Endocrine glands


  • Pineal gland
  • Hypothalamus
  • Pituitary
  • Thyroid
  • Parathyroid gland
  • Thymus
  • Adrenal glands
  • Pancreas
• Pineal gland


  • Regulation of sleep/wake cycle
• Hypothalamus


  • Connection between nervous and endocrine system, important coordinator of endocrine system

  
• Pituitary


  • Located in sella turcica, tumor here can cause compression on optic chiasm resulting in tunnel vision (loss of peripheral vision)
• Thyroid


  • Involved in a lot of pathology

  
• Parathyroid gland


  • Attached on posterior thyroid, involved in calcium metabolism
• Thymus


  • Immune function, shrinks in adulthood (important in first years of life)
• Adrenal glands


  • 2 basic structures - cortex and medulla, medulla secretes catecholamines, cortex has 3 layers which secrete cortisol, aldosterone, and secondary sex hormone
• Pancreas


  • Endocrine and exocrine function, endocrine = somatostatin, insulin, glucagon
• Glands with hypothalamus-pituitary control (HP axis)

  • Thyroid
  • Adrenal (cortex)
  • Ovary/testes

  
• Roles of endocrine system

  • Regulation of metabolism, water, and electrolytes
  • Adaptive changes (to environment)
  • Promotes growth and development
  • Sex differentiation, control of reproduction
  • Production of RBCs (EPO from kidneys)
  • Cooperation with nervous system and immune system
• Hormones


  Chemical substances released into blood and have effects on distant sites
• Glands and other tissues (kidney, intestine, myocardium) may secrete hormones
• Any given hormone affects a limited number of cells called target cells
• Target cells have receptors for specific hormones
• Peptide (Water-Soluble) Hormones


  Cannot cross cell membrane, receptor on cell surface, requires 2 messenger system to enter target cell
• Steroid (Lipid-Soluble) Hormones


  Can cross cell membrane, requires carrier protein in blood, receptor in nucleus or cytoplasm, goes directly to nucleus where they modify protein and enzyme synthesis
• Steroid hormones


  • Cortisol
  • Aldosterone
  • Testosterone, androgens
  • Estrogens, progesterone
• Steroid hormone mechanism of action is also found in thyroid hormone (called secosteroid) and vitamin D3 (dihydroxycholecalciferol)
• Primary endocrine disorder


  Happens within the endocrine gland (in HP axis) itself, can result in increased or decreased secretion

  
• Secondary endocrine disorder


  Happens when problem in pituitary
• HPT axis pathway


  1. Hypothalamus secretes TRH (thyroid releasing hormone)

  2. TRH stimulates anterior pituitary to secrete TSH (thyrotropin/thyroid stimulating hormone)

  3. TSH stimulates thyroid gland to secrete T3 (triiodothyronine) and T4 (thyroxine)

  4. Negative feedback loop: thyroid gland will send negative feedback to anterior pituitary and hypothalamus
• Types of hyperthyroidism


  • Primary Hyperthyroidism: problem in thyroid gland
  • Secondary Hyperthyroidism: problem in pituitary
  • Tertiary Hyperthyroidism: problem in hypothalamus
• Types of hypothyroidism


  • Primary Hypothyroidism
  • Secondary Hypothyroidism
  • Tertiary Hypothyroidism

  
• Factors controlling endocrine activity


  • Rate of production
  • Rate of degradation and elimination
  • Rate of binding with carrier (transporter)
  • Rate of delivery
• Negative (opposite) feedback


  TRH, TSH, T3/T4, Glycemia + insulin level, Calcemia + PTH level

  
• Positive (enhancing) feedback


  Oxytocin, estrogen
• Some hormones activated prior to release (GH, insulin) vs. activated after release (T4 -> T3)
• Abnormal liver function can cause accumulation of certain hormones (e.g. end-stage liver disease can cause gynecomastia due to inability to regulate estrogen elimination)
• Thyroxine (T4) bound to carrier 99% with half-time of 6 days, Aldosterone bound to carrier 15% with half-time of 20 min

  
• Up/down regulation of receptors on target cells
• Thymus is the site of T lymphocyte maturation
• Cardiac tissue that synthesizes hormone: ANP
• Hormones stored in vesicles do not need any transport to go into the blood, you can't get into the membrane of the target cell because they are lipid soluble so you attach to receptor instead, and from there a second messenger comes and goes into the cytoplasm of a target cell to produce the effect. Act fast
• Hormones that appear fast are degraded by catecholamines
• Patients in end stage or dialysis have low elimination of hormones
• T4 is less active than T3
• Only free hormone is active, needs to release carrier to release effect
• Low amount of hormone, target cells would bring up more receptors
• High hormones, withdraw receptors