Treatment is by surgical removal of the
growth or as much cancerous tissue as
possible. This usually involves salpingo-
oophorectomyand hysterectomyfollowed
by radiotherapyand anticancer drugs.
ovary, disorders ofDiseases and ab-
normalities of the ovaries can occur for
various reasons. Absence of ovaries, or
their failure to develop normally, is rare
and is usually due to a chromosomal
abnormality (see Turner’s syndrome).
Oophoritis (inflammation of an ovary)
may result from infections such as gon-
orrhoeaor pelvic inflammatory disease.
Ovarian cystsare common and usually
noncancerous. Polycystic ovary syndrome
is due to an imbalance of sex hormones.
Ovarian cancer (see ovary, cancer of)
occurs mainly in women over 50. Ovar-
ian failure causes premature menopause
in about 5 per cent of women.
ovary, polycystic A condition, also
called Stein–Leventhal syndrome, that
is characterized by oligomenorrhea or
amenorrhoea(scanty or absent periods),
infertility, hirsutism(excessive hairiness),
and obesity. Often, there are multiple
ovarian cysts. Most women with poly-
cystic ovaries begin menstruation at a
normal age, but after a year or two peri-
ods become highly irregular and then
cease. Hirsutism and obesity occur in
about 50 per cent of cases.
The condition results from an imbal-
ance of two gonadotrophin hormones:
follicle-stimulating hormone (FSH) and
luteinizing hormone (LH). This hormon-
al imbalance is associated with raised
levels of testosteroneand oestrogen.
Treatments include clomifene and oral
contraceptives. Polycystic ovaries are
often associated with high oestrogen
levels in the body, which increase the
risk of endometrial cancer (see uterus,
cancer of); treatment with progesterone
may be recommended for this problem.
overbiteOverlapping of the lower front
teethby the upper ones. A slight degree
of overbite is normal as the upper jaw is
larger than the lower jaw. In malocclu-
sion, overbite may be greater than
normal or the lower teeth may project
in front of the upper teeth.
overbreathingA common name for
hyperventilation.
overcrowding, dentalExcessive crowd-
ing of the teethso that they are unable
to assume their normal positions in the
jaw. Dental overcrowding is commonly
inherited and may occur because the
teeth are too large for the jaw or the jaw
is too small to accommodate the teeth.
Premature loss of primary molar (back)
teeth can cause the permanent teeth
beneath them to move out of position
and crowd the teeth further forward.
Overcrowded teeth may lead to maloc-
clusionor may prevent certain teeth from
erupting through the gum (see impac-
tion, dental). They can be difficult to clean,
increasing the risk of dental decay (see
caries, dental) and periodontal disease.
Teeth may need to be extracted to
allow room for others. Usually an ortho-
dontic applianceis fitted to the remaining
teeth to position them correctly.
over-the-counter (OTC) drugA drug
that can be bought without a prescrip-
tion at a chemist’s or other store.
overuse injuryAlso called repetitive
strain injury, a term, for any injury caused
by repetitive movement of part of the
body. Symptoms include pain and stiff-
ness in the affected joints and muscles.
Examples include epicondylitis: painful
inflammation of one of the bony promi-
nences at the elbow, caused by the pull
of the attached forearm muscles during
strenuous activities (see golfer’s elbow;
tennis elbow). Overuse injuries of the fin-
gers, thumb, and wrist joints may affect
assembly-line and keyboard workers, and
musicians; injuries of the neck may affect
violinists. Rest relieves the symptoms.
A change in the technique used during
the activity may prevent recurrence.
overweightSee obesity.
ovulationThe development and release
of an ovum(egg) from a follicle within
an ovary. During the 1st half of the
menstrual cycle, follicle-stimulating hor-
mone(FSH) causes several ova to mature
in the ovary. At mid-cycle, luteinizing
hormone(LH) causes 1 ripe ovum to be
released. Signs of ovulation include a
rise in body temperature, changes in the
cervical mucus, and sometimes mild
abdominal pain (see mittelschmerz). A
yellow mass of tissue called the corpus
luteum, which forms from the follicleOVARY, DISORDERS OF OVULATION
O