Bma Illustrated Medical Dictionary

and abdomen; in women, it occurs on
the breasts, hips, and thighs.
adjuvantA substance that enhances
the action of another substance in the
body. The term is usually used to des-
cribe an ingredient added to a vaccine
to increase the production of antibodies
by the immune system, thus enhancing
the vaccine’s effect. Adjuvant chemother-
apy is the use of anticancer drugsin
addition to surgical removal of a tumour.
Adlerian theoryThe psychoanalytical
ideas set forth by the Austrian psychia-
trist Alfred Adler. Also calledindividual
psychology, Adler’s theories were based
on the idea that everyone is born with
feelings of inferiority. Life is seen as a
constant struggle to overcome these
feelings; failureto do so leads to neuro-
sis. (See also psychoanalytic theory.)
adolescenceThe period between child-
hood and adulthood, which broadly
corresponds to the teenage years. Ado-
lescence commences and overlaps with,
but is not the same as, puberty.
ADPThe abbreviation for adenosine di-
phosphate, the chemical that takes up
energy released during biochemical reac-
tions to form ATP(adenosine triphos-
phate), the body’s main energy-carrying
chemical. When ATP releases its energy,
ADP is reformed. (See also metabolism.)
adrenal failureInsufficient production
of hormones by the adrenal cortex (the
outer part of the adrenal glands). It can
be acute or chronic. Adrenal failure may
be caused by a disorder of the adrenal
glands, in which case it is called Addi-
son’s disease, or by reduced stimulation
of the adrenal cortex by ACTH, a hor-
mone produced by the pituitary gland.
adrenal glandsA pair of small, trian-
gular endocrine glands located above
the kidneys. Each adrenal gland has
2 distinct parts: the outer cortex and the
smaller, inner medulla.
The cortex secretes aldosterone, which,
together with hydrocortisone and cor-
ticosterone and small amounts of
androgen hormones helps to maintain
blood pressure. Hydrocortisone controls
the body’s use of fats, proteins, and car-
bohydrates and is also important in
helping the body to cope with stress.
Hydrocortisone and corticosterone also

suppress inflammatory reactions and

someactivities of the immune system.

Production of adrenal cortical hor-

mones is controlled by ACTH, which is

produced in the pituitary gland.

The adrenal medulla is part of the

sympathetic autonomic nervous system.

In response to stress, it secretes the

hormones adrenaline (epinephrine) and

noradrenaline (norepinephrine),which

increase heart-rate and blood flow.

adrenal gland disordersA range of

uncommon but sometimes serious dis-

orders due to deficient or excessive

production of hormones by one or both

of the adrenal glands.

A genetic defect causes congenital

adrenal hyperplasia,in which the ad-

renal cortex is unable to make sufficient

hydrocortisone and aldosterone, and

androgensare produced in excess. In

adrenal failure, there is also deficient

production of hormones by the adrenal

cortex; if due to disease of the adrenal

glands, it is called Addison’s disease.

Adrenal tumoursare rare and generally

lead to excess hormone production.

In many cases, disturbed activity of

the adrenal glands is caused, not by

disease of the glands themselves, but

by an increase or decrease in the blood

level of hormones that influence the

action of the adrenal glands. For exam-

ple, hydrocortisone production by the

adrenal cortex is controlled by ACTH,

which is secreted by the pituitary gland.

Pituitary disorders can disrupt produc-

tion of hydrocortisone.

ADJUVANT ADRENAL GLAND DISORDERS

A

Blood vessel

Kidney

Kidney

Adrenal

cortex

Adrenal

gland

LOCATION

ADRENAL GLANDS

Adrenal

medulla

Fat

STRUCTURE OF ADRENAL GLAND