PITUITARYTUMOURS
DISORDERSOFTHE PITUITARYGLAND
Any abnormality of the pituitary gland
usually means that it produces either
too much or too little of one or more
hormones, causing changes elsewhere
in the body. Locally, serious effects may
be caused by enlargement of the gland;
for example, it may press on the nearby
optic nerves and cause visual defects.
Congenital and genetic disorders
Deficiency of
grow th h o rm o n e
may be a
genetic disorder, or it may be due to
congenital absence or undergrowth of
the pituitary or to damage to the gland
sustained during birth. Whatever the
cause, deficiency of growth hormone
leads to
s h o rt sta tu re
.
Congenital growth hormone
deficiency may also be associated with
deficiency of other pituitary hormones,
notably
A CTH
(adrenocorticotrophic
hormone),
g o n a d o tro p h in h o rm o n e s
,
and
thyroid-stimulating hormone (TSH).
Tumours
P ituita rytu m o u rs
are usually noncancerous
but may cause either overproduction of
pituitary hormones (hyperpituitarism) or
underproduction (hypopituitarism), as well
as headaches and loss of the visual field.
Injury
Birth injury may cause loss of pituitary
function, as may head injuries at any age.
Impaired blood supply
Rarely, the pituitary may suffer deprivation
of its blood supply as a result of pressure
exerted on its blood vessels from a growing
tumour. This may cause a sudden loss of
pituitary function, which may be fatal, or a
more gradual loss, which produces signs of
general underactivity of the gland.
A similar deprivation of blood supply
may occur as a complication of massive
blood loss associated with childbirth
(Sheehan’s syndrome).This may lead to
failure of milk production, and a wide
range of secondary effects due to the
resultant underactivity of other
endocrine glands. Impaired blood
supply may also occur due to
v a sc u litis
or pressure on the gland from an
a n e u rysm
of a nearby artery.
Radiation
Radiotherapy for a pituitary tumour may
cause general underactivity of the gland.
INVESTIGATION
Techniques include analysis of pituitary
hormones in the blood or urine, and of
hormones from other endocrine glands
under pituitary control; pituitary
X-rays,
CTscanning,
or
MRI; angiography,
to
show blood-vessel displacement by a
pituitary tumour; and, possibly, a visual
field test (see
vision tests).
P
I t r e g u l a t e s t h e a c t i v i t i e s o f o t h e r e n d o -
c r i n e g l a n d s a n d m a n y b o d y p r o c e s s e s
( s e e
e n d o c rin e s y s t e m ).
F o r i n f o r m a t i o n o n d i s o r d e r s t h a t c a n
a f f e c t t h e p i t u i t a r y g l a n d , s e e t h e p i t u -
i t a r y g l a n d d i s o r d e r s b o x .
STRUCTURE
T h e p i t u i t a r y g l a n d i s a p e a - s i z e d s t r u c -
t u r e a t t a c h e d b y a s t a l k o f n e r v e f i b r e s
t o
t h e
h y p o th a la m u s ,
a
r e g i o n
o f t h e
b r a i n j u s t a b o v e t h e
g l a n d . T h e h y p o -
t h a l a m u s c o n t r o l s p i t u i t a r y f u n c t i o n b y
n e r v o u s s t i m u l a t i o n a n d b y s e c r e t i n g s u b -
s t a n c e s c a l l e d h o r m o n e - r e l e a s i n g f a c t o r s .
T h e p i t u i t a r y g l a n d c o n s i s t s o f t h r e e
l o b e s :
t h e
a n t e r i o r ,
t h e
i n t e r m e d i a t e ,
a n d t h e p o s t e r i o r .
FUNCTIONS
T h e t h r e e l o b e s o f t h e p i t u i t a r y p r o d u c e
a r a n g e o f h o r m o n e s . F o r f u r t h e r i n f o r -
m a t i o n
o n
t h e
i n d i v i d u a l
p i t u i t a r y
h o r m o n e s
a n d
t h e i r
e f f e c t s ,
s e e
t h e
i l l u s t r a t e d b o x , o v e r l e a f .
T h e a n t e r i o r l o b e p r o d u c e s m o s t o f t h e
p i t u i t a r y h o r m o n e s i n c l u d i n g
g ro w th h o r-
m o n e ,
p ro la c tin ,
A C T H
( a d r e n o c o r t i c o -
t r o p h i c h o r m o n e ) , T S H ( t h y r o i d - s t i m u l a t -
i n g
h o r m o n e ) ,
a n d
t h e
g o n a d o t ro p h in s
F S H
( f o l l i c l e - s t i m u l a t i n g
h o r m o n e )
a n d
L H
( l u t e i n i z i n g
h o r m o n e ) .
T h e
i n t e r -
m e d i a t e
l o b e
s e c r e t e s
m e l a n o c y t e - s t i m -
u l a t i n g h o r m o n e ( M S H ) . T h e s e c r e t i o n o f
t h e s e h o r m o n e s i s t r i g g e r e d b y h o r m o n e -
r e l e a s i n g f a c t o r s f r o m t h e h y p o t h a l a m u s .
T h e p o s t e r i o r p i t u i t a r y l o b e s e c r e t e s
A D H
a n d
oxyfoc/'n
. T h e s e h o r m o n e s a r e a c t u a l l y
p r o d u c e d i n t h e h y p o t h a l a m u s , a n d p a s s
d o w n n e r v e f i b r e s t o b e s t o r e d i n t h e p o s -
t e r i o r l o b e u n t i l t h e y a r e n e e d e d .
p itu ita r y tu m o u rs
G r o w t h s i n t h e
p it u it a r y g la n d .
P i t u i t a r y
t u m o u r s
a r e
r a r e ,
a n d
u s u a l l y
n o n -
c a n c e r o u s , b u t t h e y c a n p u t p r e s s u r e o n
t h e
o p t ic n e rv e s ,
c a u s i n g v i s u a l d e f e c t s .
CAUSES AND SYMPTOMS
T h e
c a u s e s
o f
p i t u i t a r y
t u m o u r s
a r e
u n k n o w n . O n e t y p e , c a l l e d a n e n d o c r i n e
i n a c t i v e t u m o u r ,
c a u s e s t h e d e s t r u c t i o n
o f s o m e o f t h e h o r m o n e - s e c r e t i n g c e l l s
i n
t h e
p i t u i t a r y
g l a n d .
T h i s
l e a d s
t o
i n a d e q u a t e h o r m o n e p r o d u c t i o n , c a u s -
i n g p r o b l e m s s u c h a s t i r e d n e s s , l o s s o f
a p p e t i t e ,
s y m p t o m s
o f
h y p o th y ro id is m
( u n d e r a c t i v i t y
o f
t h e
t h y r o i d
g l a n d ) ,
a n d c e s s a t i o n o f m e n s t r u a l p e r i o d s
o r
r e d u c e d s p e r m p r o d u c t i o n .
T u m o u r s m a y a l s o c a u s e t h e g l a n d t o
p r o d u c e
e x c e s s i v e
a m o u n t s
o f c e r t a i n
h o r m o n e s . T u m o u r s o f t h e a n t e r i o r l o b e
c a n
c a u s e
v a r i o u s
d i s o r d e r s .
O v e r p r o -
d u c t i o n
o f
g r o w t h
h o r m o n e
c a u s e s
g ig a n t is m
o r
a c ro m e g a ly .
E x c e s s t h y r o i d -
s t i m u l a t i n g
h o r m o n e
( T S H )
c a n
l e a d
t o
h y p e rt h y ro id is m .
E x c e s s a d r e n o c o r t i c o -
t r o p h i c
h o r m o n e
( A C T H )
c a n
c a u s e
C u s h i n g ’s
d i s e a s e
( s e e
C u s h in g ’s s y n -
d ro m e
) .
A n
i n c r e a s e
i n
p r o l a c t i n
c a n
c a u s e
g a la c t o rrh o e a
( a b n o r m a l m i l k p r o -
d u c t i o n ) ,
a m e n o rrh o e a
( a b s e n c e o f m
e n -
s t r u a l p e r i o d s ) , a n d
in fe rt ilit y
i n w o m e n .
I n
m e n ,
i t
c a n
c a u s e
im p o t e n c e ,
i n -
f e r t i l i t y ,
fe m in iz a t io n ,
a n d g a l a c t o r r h o e a .
T u m o u r s t h a t a f f e c t t h e p o s t e r i o r p i t u -
i t a r y
m a y
d i s r u p t
t h e
p r o d u c t i o n
o f
a n t i d i u r e t i c h o r m o n e ( A D H ) a n d l e a d t o
d ia b e t e s in s ip id u s .
P r e s s u r e
f r o m
t u m o u r
e n l a r g e m e n t
m a y
c a u s e
h e a d a c h e s ,
c r a n i a l
n e r v e
p a ra ly s is ,
a n d d e f e c t s o f v i s i o n .
DIAGNOSIS AND TREATMENT
D i a g n o s i s i s m a d e u s i n g
b lo o d te s ts
t o
m e a s u r e h o r m o n e l e v e l s ; X - r a y s ;
M R I
o f
t h e p i t u i t a r y ; a n d , o f t e n ,
v is io n te sts.
T r e a t m e n t
m a y
c o n s i s t
o f
s u r g i c a l
r e m o v a l
o f
t h e
t u m o u r ,
ra d io t h e ra p y
,
h o r m o n e
r e p l a c e m e n t ,
o r
a
c o m
b i n a -
t i o n
o f
t h e s e
t e c h n i q u e s .
T h e
d r u g
b ro m o c rip t in e
m a y b e u s e d ; i t c a n r e d u c e
p r o d u c t i o n
o f
c e r t a i n
h o r m o n e s
a n d
s h r i n k s o m e t u m o u r s .
p ity r ia s is a lb a
A c o m
m o n s k i n c o n d i t i o n o c c u r r i n g i n
c h i l d h o o d a n d a d o l e s c e n c e , p a r t i c u l a r l y
i n d a r k - s k i n n e d c h i l d r e n , t h a t i s c a u s e d
b y
m i l d
e c z e m a
.
I r r e g u l a r ,
f i n e ,
s c a l y ,
p a l e
p a t c h e s
a p p e a r
o n
t h e
f a c e ;
t h e
p a t c h e s m a y b e
m o r e
n o t i c e a b l e
a f t e r
e x p o s u r e t o t h e s u n ,
b e c a u s e t h e y t a n
p o o r l y .
T h e
c o n d i t i o n
c a n
u s u a l l y
b e
c l e a r e d u p w i t h
e m o llie n t s
.
610
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