Endocrine System

• Hormones are chemical substances secreted by endocrine cells that regulates metabolic activities of other cells in the body.
• What are the major endocrine organs?

  • Pineal gland
  • Hypothalamus
  • Pituitary gland
  • Thyroid gland
  • Parathyroid glands
  • Thymus
  • Adrenal glands
  • Pancreas
  • Ovaries
  • Testis
• Hormones are synthesized and released in response to humoral stimuli, neural stimuli, and hormonal stimuli
• What are the three types of hormones?

  1. Steroids (from cholesterol)
  2. Peptides (chains of amino acids)
  3. Monoamines (single amino acid)
• what is the pituitary gland?

  • makes hormones that instructs other glands to make hormones
  • Located at the base of the brain beneath the hypothalamus
  • has 2 lobes: posterior pituitary lobe and anterior pituitary lobe
• Hypopituitarism is when the pituitary gland does not produce one or more of its hormones or not enough of them
• what does the posterior pituitary lobe do?


  • aka neurohypophysis
  • regulates oxytocin and ADH
  • carried by nerves (neural tissue)
  • not regulated by hypothalamus
• Antidiuretic Hormone (ADH) is also known as vasopressin that retains water by kidneys decreasing urine production
• What does the anterior pituitary lobe do?


  • regulated by the hypothalamus
  • aka adenohypophysis (glandular tissue)
  • releases ACTH, LH, TSH, prolactin, growth hormone
• Human growth hormone


  • aka somatotropin
  • in children, it stimulates growth. In adults, it helps maintain skeletal muscles and bones 
  • promotes protein synthesis and encourages use of fats for fuel
• Thyroid-stimulating hormone (TSH)


  • aka thyrotropin
  • stimulates the thyroid gland to produce thyroid hormones
  • stimulated by thyrotropin-releasing hormone (TSH)
  • High TSH = hypothyroidism (lack of thyroid hormones)
  • Low TSH = hyperthyroidism
  • Low TSH = hypothyroidism