70% to 80% of young adults are affected by
acne, a common skin disorder affecting the face, neck, chest,
and back. Though not physically disabling, this skin disease
can cause severe emotional stress due to permanent facial scarring
and due to its persistence. It usually occurs during difficult
period of growing up and development of a young adult. Appropriate
treatment is needed to dramatically improve the lives of the
affected individuals.
Plugged sebum and keratin lodged in the follicular ducts called
comedones are the primary lesions of acne. These are usually
non-inflammatory. However, if these comedones rupture the follicular
wall, an inflammatory reaction to the sebum produces papules,
pustules, and cysts. Propionibacteria, anaerobic bacterium that
lives in the microenvironment of hair follicles, also promotes
inflammatory lesions. If the immune system detects bacteria
in the ruptured hair follicles, it responds and tries to kill
them, resulting to inflammatory lesions. These lesions may produce
scars if the inflammation is intense enough.
What causes the increased production of sebum and does this
lead to acne? Several factors maybe involved in this process.
Androgens
Androgens have been shown in numerous studies to be a major
contributory factor in the production of acne. The gonads and
the adrenal glands produce most androgens. However, some androgens
are also produced locally by the sebaceous glands from the adrenal
precursor hormone DHEA.
The interaction of the major androgens like testosterone with
the sebaceous glands through androgen receptors is well known.
However, the cellular or molecular mechanism by which androgens
stimulate sebum production is not yet fully understood. The
cells of the basal layer of the sebaceous glands and the outer
root sheath, keratinocytes of the hair follicle, contains the
androgen receptors.
These five pieces of clinical evidence shows the important
role of androgens in stimulating sebum production.
- The higher serum levels of DHEAS (a precursor of testosterone)
in pre-pubertal period causes the development of early acne.
- The lack of functional androgen receptors in androgen-intensive
subjects inhibits sebum production thus prevents acne
development.
- Tumors of the ovary of adrenal gland that produces
androgen are also associated with acne.
- Testosterone and
DHEAS administration systematically also increases the size
and secretion of sebaceous glands.
- Higher serum androgen
levels often cause severe acne.
Hormones, therefore, are clearly involved in acne development.
Acne Causing Stress
The onset of acne in women coincides with menarche, although
its prevalence varies widely. It has also been interestingly
identified that women over 25-years of age, some even in their
forties, have low grade persistent acne. Stress induced secretion
of adrenal androgens is believed to be the cause of this condition.
Until recently, emotional stress has been anecdotally linked
to acne because objective assessment has been lacking. Studies
though, show that there is statistical correlation between stress
and acne.
Role of Growth Hormones in Acne Development
Produced by the pituitary gland, growth hormone stimulates
growth by acting on the liver and peripheral tissues to stimulate
insulin growth factor production (IGF), also known as somatomedians.
The more prevalent IGF-1 and also the IGF-2 are the two types
of IGF, which is a known promoter of keratinocyte activity,
and increased sebaceous gland oil production. Because of this
sebaceous gland oil increasing production property, growth hormone
may be involved in acne development. During adolescence, the
growth hormone secretion and IGF-1 serum levels are at their
highest, which explains why acne is also widespread at this
age. Production of IGF-1 molecules can also happen locally in
the skin where they can interact with the IGF receptors on the
sebaceous glands, increasing sebum production. The development
of acne in teens may also be contributed to the growth that
occurs in them.
Diet Can Cause Acne
Development of acne due to diet has been traditionally dismissed
as a myth. However, the observation that acne is almost absent
in non-westernized cultures and the presence of acne in western
or westernized cultures suggests that diet and the environment
could be causes. The high glycemic diet of the West, as suggested
by one study, could cause acne by producing hyperinsulinemic
states.
Genetic Factors in Acne Development
Facial oiliness or seborrhea is another factor believed to
be a pre-conditioned for acne. The genetic make up of a person
partly affects the degree of oiliness that an individual experiences.
As some genes code for a higher level of sebaceous gland activity
and oil production, they may also play a role in the kind of
sebum that is produced. Some genes also code for higher levels
of the production of cholesterol, a relatively sticky substance.
Cholesterol produced by the sebaceous glands serves as the binding
agent of the oils and the dead cells in the hair follicle canal,
which forms the nucleus of the sebum plug.
