thyroid gland - found right below Adam’s apple in the neck 

• promotes growth/brain development
• responsible for metamorphosis in amphibians
• calcitonin - lowers blood calcium level
• also releases triiodothyronine (T3) and thyroxine (T4)

parathyroid glands - 4 small glands attached to the thyroid gland 

• stimulates release of calcium from bones
• parathyroid hormone (PTH) - 1 of 2 hormones humans can’t live w/o
  • released in response to falling calcium levels
• osteoclasts (bone cells) stimulated to release calcium
• kidneys stimulated to reabsorb calcium in urine by vitamin D

adrenal glands - found above kidneys, contains adrenal medulla (inside), adrenal cortex (outside) 

• adrenal medulla - receives neural info from sympathetic division
  • secretes epinephrine/norepinephrine
  • produces fight or flight response due to sympathetic nerves
• adrenal cortex - produces steroids (called corticosteroids)
  • maintains glucose levels, stimulates gluconeogenesis
  • glucocorticoids - breaks down muscle proteins into amino acids, amino acids into glucose
  • aldosterone - 1 of 2 hormones humans can’t live w/o, stimulates kidneys to reabsorb Na+ and secrete K+

pancreas - located next to stomach, connected to duodenum 

• secretes bicarbonate and enzymes into small intestine
• islets of Langerhans - secretes insulin in beta cells, glucagon in alpha cells
• type I diabetes - lacking insulin-secreting cells, but have insulin injections
• type II diabetes - cells have reduced sensitivity to insulin
  • can only be helped by diet
• insulin stimulates absorption of glucose
• glucagon stimulates hydrolysis of glycogen >> antagonistic to insulin

other endocrine glands - 

• molting/metamorphosis used for growth since exoskeletons don’t expand
  • brain hormone secreted >> ecdysone produced in thorax >> molting
  • juvenile hormone used up >> metamorphosis no longer inhibited
• sex steroids - estrogen/progesterone in females, testosterone in males
  • androgens - determines male sex characteristics, overcomes the default female setting in mammals
  • estrogen - determines female sex characteristics, overcomes the default male setting in birds
• pineal gland - aka “third eye”, secretes melatonin to regulate amount of sleep
  • maintains sleep, seasonal changes during migration, hibernation, mating
• thymus - produces T cell lymphocytes
  • found in front of chest

endocrine-disrupting chemicals - low concentrations of target cells in blood 

• small change in concentration >> big changes in effect on organ
• agonist - chemical that mimic hormone
  • can bind to receptor proteins
• antagonist - doesn’t mimic hormone, but stops hormones from binding