Depression in physiology and medicine refers to a lowering, in particular a reduction in a particular biological variable or the function of an organ. It is in contrast to elevation.

For example, it is possible to refer to "depressed thyroid

Thyroid

The thyroid gland or simply, the thyroid , in vertebrate anatomy, is one of the largest endocrine glands. The thyroid gland is found in the neck, below the thyroid cartilage...

 function" or to a depression of blood flow in a particular area.

Further examples:

• Depression of the central nervous system
  Central nervous system
  The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
  
   of an animal may be expressed as drowsiness or sleep, lack of coordination and unconsciousness
  Unconsciousness
  Unconsciousness is the condition of being not conscious—in a mental state that involves complete or near-complete lack of responsiveness to people and other environmental stimuli. Being in a comatose state or coma is a type of unconsciousness. Fainting due to a drop in blood pressure and a...
  
  .