Happy holidays!
Brown fat is a special fat that functions to generate heat
for the body. Brown fat usually locates in the neck, shoulder, and along the
spine. Brown fat is common in newborn babies and its purpose in babies is to
protect babies from hypothermia. This is important as babies have a relatively
larger body surface area and are more sensitive to ambient temperature. Brown
fat is gradually lost as we become adults but persists in some. Brown fat is
activated to produce heat when the body senses that its temperature may drop. The
way the brown fat is activated to produce heat is by catecholamines.
In people with pheo, brown fat can be activated, likely due
to the catecholamines released by pheo. The extent of brown fat activation is
very variable. Most older people with pheo don’t show much brown fat activation.
In young adults with pheo, brown fat activation can be extensive. Brown fat is
very positive in FDG PET and somewhat positive on DOTATATE PET, so it can cause
concern to those uninitiated on this phenomenon. Most radiologists can tell
brown fat from pheo very readily. Thus brown fat activation associated with
pheo is mostly an interesting observation; it can also help make the pheo
diagnosis in a person with adrenal mass and brown fat activation.
Dr. Pheo
