first component the sinus
and mastoid are small air spaces within skull bone former closely associated with air ways and later to hearing system
the findings possibly indicating some infection.
you need consult doctor
the pituitary gland
controls all the body functions guided by hormones- and is main center for over all control
is fluid filled small bubble in body- its presence in pituitary gland can be by birth / on later stage in life without any consequences, Or can cause comprehensive effect on gland and disrupt hormonal
functions. In your case and with given MRI findings the former appears true- i. e. not much of problem
Still my suggestion is meet your doctor.