The endocrine system is made up of glands that produce and secrete hormones which regulate organs and bodily functions. Major glands include the hypothalamus, pituitary, thyroid, and reproductive organs. Hormones are chemical messengers that coordinate different body parts. The endocrine system uses feedback loops so hormone levels remain stable in the bloodstream. Exocrine glands also secrete substances but release them onto organ surfaces through ducts rather than into the bloodstream. Pernicious anemia is a type of anemia caused by the inability to absorb vitamin B12 due to lack of intrinsic factor. Sickle cell anemia is an inherited blood disorder where red blood cells become misshapen and can block blood vessels,