Cardiologists

• Cardiologists specialize in the diagnosis and treatment of heart conditions. Some typical specialties of cardiologists include congenital heart defects, artery disease and heart failure.
  
  

Gastroenterologists

• Gastroenterologists specialize in diagnosing and treating disorders of the gastrointestinal tract, the organs from mouth to anus. Gastroenterologists study such subjects as cancer of the digestive tract, stomach acidity levels and ulcer production.
  
  

Hematologists

• Hematologists specialize in diagnosing and treating disorders of the blood, the bone marrow and the circulatory system. They study such subjects as leukemia, lymphoma, hemophilia and the properties of stem cells.
  
  

Endocrinologists

• Endocrinologists study the behavior of the endocrine system, which produces hormones. Traditionally, a hormone is defined as a chemical secreted by an organ that is then transported through the blood to another organ for a specific purpose.
  
  Endocrinologists work to identify and treat disorders of the pituitary, thyroid and other vital glands.
  
  

Other Types of Internists

• Other types of internists include nephrologists (who specialize in the kidneys), pulmonologists (specializing in the lungs), rheumatologists (specializing in the joints and soft tissues), immunologists (specializing in the immune system) and medical oncologists (specializing in non-surgical cancer treatments).